While I love radiators, I hate using fossil fuels
SusanHanway
| Posted in Energy Efficiency and Durability on
I live in an 1890 Victorian in Southern Pennsylvania, heated by oil. While I love radiators, I hate using fossil fuels! Is there a way to use green technology to use less oil? My methods to date have been uncomfortable – installing a wood stove.
Is there a way of boosting the boiler with green energy? Would geothermal help? I’m newly divorced and ignorant about systems!
Thanks, Susan
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Susan. I suspect follow-on posters will suggest that improving your home with more insulation and air sealing will be the best way to mitigate your fossil fuel use. Also, while opinions vary, heating with wood is often considered to be a pretty good way to reduce your carbon footprint. You might want to start by having an energy audit done on your home. Many utilities offer them for free or at a reduced cost.
Thanks Steve,
I'll do that.
I paid for an energy audit years ago that was a bit of a hoax, but thanks for the reminder of PECO's audit. One company came in and blew insulation in the attic and basement. However, he said that the walls aren't able to have stuff blown in, as they're too thin. What do you think about wallpapering with fabric or putting cork on the walls?
Steam, or pumped hot water?
Number of zones?
Model name of the existing boiler and it's BTU-input and D.O.E. output numbers on the nameplate?
With a fuel use history you can calculate the approximate heat load of the house where-is/as-is, prior to any insulation & air sealing up grades. If you are on an regular oil fill-up service they typically stamp a "K-factor" on the end of the slip. If you have some mid or late winter fill up slips, what are the K-factors?
How much wood do you burn per year, and how much oil, approximately?
A ZIP code would give a better shot at guessing the 99% outside design temp, and average wintertime outdoor temps, which are necessary to analyze the problem . (Southern PA covers a range of weather & climate, from US climate zone 4A, to the middle of zone 5A.)
I think fabric and cork would be a waste of money. But redo the audit and provide the information Dana requested. He will reward you with a ton of useful information. This site is an incredible resource for homeowners who want to do the right thing by the planet and their pocket books.
Thanks Steve and Dana,
Yes, an incredible resource if you're willing to put up with my ignorance! I very much appreciate the help, and want to add that while I don't want to spend money wastefully, I am an environmentalist from way back and can afford to change systems. Is there a way to make geothermal help? (cringe!)
I don't know if it's steam or hot water! (cringe again!) How do I know the number of zones? There's only one thermostat for the house....
The Boiler was made by Peerless Boilers Series WBV/WV Boiler. There are three columns to the right of "Input" : 1.50 1.25 and .75 gallons/hr.
Under DOE Heating Capacity the three columns read: Water 151000 BTU/hr. Water 117000 BTU/hr. Water 117000 BTU/hr.
In looking at last winter's invoices, I don't see a "K Factor". They say "Gallons corrected to 60.0F" but otherwise I only see "sale no., meter no. unit ID, driver no " type of information...
Last winter I burned a cord and a half of wood. (lovely warmth!) My zip code is 19380.
THANK YOU!
Numbers from test results from an audit are pretty important as it pertains to making recommendations about what may be possible .
Odds are pretty good that your radiators are oversized such that low temps can be substituted for the high temps you are now using . This could allow for different types of equipment to be used . There is also a high possibility to use a water to water heat pump for most of the season connected to mass and a wood burning appliance .
Knowing or recommending anything though would require some more accurate information . Posting electric and gas rates available in your area can help in beginning to move in a specific direction and exploring different options until results from a PECO audit are obtained . I do highly doubt that Geo thermal ( GSHP ) would be a good option but then again , that would be based on the balance between utility rates and what the home requires .
Susan,
If you have a hot-water distribution system rather than a steam system, it's possible to invest in a ground-source heat pump system (sometimes called a "geothermal" system) and to hook up that system to your existing hot-water distribution pipes.
I don't recommend that you do that, however -- mainly because it is so expensive that it's hard to justify the cost. That type of system will cost between $18,000 and $40,000.
In your case, if for some reason you wanted to invest $18,000 to $40,000, it would be much better to invest the money in envelope improvement measures: air sealing work, insulation improvements, and perhaps better windows.
If you have any money left over, you might want to invest in a photovoltaic (PV) system and one or two ductless minisplit units. The future is all-electric.
But, if you are romantically attached to radiators, you may end up ignoring my advice.
Not so fast Martin .
https://www.linkedin.com/groups/62696/62696-6161535840448241668
Water to Water HPs are electric also and can do your space heating and domestic hot water . Since you already have emitters in place a retro fit is not only possible but may offer better value , definitely more comfortable than wall warts .
No surprise that PV and wall warts are given as best option here at GBA .
Richard,
Of course heat pumps are electric -- whether you are talking about a ground-source heat pump or an air-to-water heat pump. Choosing one of these heat pumps will definitely lower or eliminate Susan's fossil fuel consumption.
The problem with the ground-source heat pump option, as I noted, is the high cost of these systems.
The problem with air-to-water heat pumps is that they are so unusual that it's hard to find a mechanical engineer to design the system, and it's hard to find a heating contractor to troubleshoot and maintain the system.
For more information on air-to-water heat pumps, see Air-to-Water Heat Pumps.
A water to Water HP does not necessarily require there to be a ground source Martin . It's hard to find a mechanical engineer that is qualified to install any system that actually works in residential or commercial spaces for that matter . Reason being , they are mechanical engineers and think that there must be a mechanical solution to a physical issue . Same issue with contractors , , same issue with those who install mini splits . The issue with contractors , specifiers should not force people to go one route or another . They all need to be trained properly in the less is more forum to get prices down on their particular technology .
How bout doing an impartial piece on different types of systems and including some that require a refrigerant with a 0 GWP like R-718 inside the built environment ?
I looked up the model boiler you have, and it is available in both hot water and steam models, so it's hard to be sure which you have. The label data you list sounds like it is hot water, but it's possible that that is just a standard label that tells you how much heat it would be put out if it was set up for water, but it's actually set up for steam. If you were to post a picture of the boiler and/or a picture of a radiator we could probably recognize which it is.
If you put hot water from a heat pump into radiators that are now run from a boiler, the heat output is much less than it would be now. That could be OK, if the initial system was oversized, and if you do enough envelope improvements. As a bonus, the envelope improvements would reduce the size and cost of the heat pump needed, and reduce the size and cost of the associated well drilling. So I would recommend putting money into the envelope first, and then coming back to considering heating systems. Susan did indicate that she's done some of that, but perhaps there are still opportunities that are reasonably low cost.
If you can't quite make it work after the envelope improvements--if the radiators can't put out enough heat with the lower temperature water, you have the option to add more radiators (you like radiators, right?), which is what I did in my house, or to add "fan coil" units that are basically fan-boosted radiators, which can put out a lot more heat from a small unit, so you might only need to add a few of those. There are nice, efficient, quiet ones available now from HTP and from Chiltrix. I wish those had been available back when I was putting in my system.
A way to split the difference between the standard recommendation of mini-split air source heat pumps and geomthermal water-water systems is an air-to-water heat pump, such as the one available from Chiltrix. It could deliver hot water to radiators, at a little lower efficiency than the geo system, but with a much lower installation cost. You might need to gang several of their units to get enough heat.
One disadvantage of converting your radiators to a new source like that is that it becomes a unique custom designed system and finding the right expertise to get it designed and installed can be difficult. And done wrong, it can have poor performance and low efficiency.
In any case the first step is to figure out how much heat you need. Without a K-factor on your bill, it might be possible to estimate from the total gallons used for the season. Or you might be able to call the oil company and ask them if they have a K factor. A difficulty with estimating from total gallons used would be that some of that usage is for hot water...is your hot water heating also from oil?
Richard,
Most HVAC experts use the term "ground-source heat pump" to include heat pumps that use a lake or pond as the heat source. But you're right -- you can use a lake or pond, either directly or indirectly, as a heat source.
A system that uses water from a drilled well as a heat source is also commonly referred to a ground-source heat pump.
Susan. You can determine how carbon-intensive your power needs are by going to this site. https://oaspub.epa.gov/powpro/ept_pack.charts
PECO is a bit better than the national average but still uses coal, gas, and oil to meet about half of its generating needs. As Martin noted, installing solar voltaics would allow you to reduce your personal carbon footprint.
Improving the air sealing and insulation on your home is the first step, however. It will drive any other decisions you make. If you don't have confidence in PECO's program for reducing energy, consider hiring your own energy expert by searching the member list at http://www.resnet.us.
Thanks so much everyone! I will call my oil company to find out whether it is steam or hot water driven.
Thank you so much everyone!
My electricity is 100% from wind power, due to a program PECO accepted. I pay $.1299/KWH and I pay $2.69 per gallon in oil.
As I am not handy, I agree that finding someone to install and maintain a heat pump integrated into the system might be a challenge, but I am intrigued and will look into it..
I love the heat of radiators but hate the idea of using oil, and keep my thermostat at 55, supplementing with the wood stove and electric space heaters. The idea of an electric heat pump working with the radiators is wonderful. Martin and Steve, would the solar system be worth cutting old trees? Trade-offs, trade-offs!
Charlie, I will add up how much oil I used, but my daughter is living with me after college, and this winter I will not be able to be so stoic!
I will call PECO today for an energy audit.
THANK YOU again. I feel so lucky!
Cutting Old Growth trees is a very environmentally unfriendly prospect . Those trees would be on the South side which would increase your cooling demand . You already have a renewable source for electric anyway .
How do you presently make hot water ?
Do you keep the temp at 55* by choice or just to save on fuel oil and/or burn less ? There are many options to use and many ways to hedge against using fossil fuels or keeping their use to a bare minimum .
A heat pump of some kind sounds like a great opportunity for you, given those prices. A heat pump's performance is measured by COP, which is the ratio of heat output to electric energy input. The COP varies with outside temperature and lots of other things, but is generally in the range of 2 to 4, sometimes up to 5 or 6. That lowest COP of 2 only happens with an air-source heat pump on the coldest days in a cold climate. And even with a COP of just 2, you'd be paying less for heat than you are now. In practice, you'd probably pay less than half what you are paying now, not even counting any envelope improvements. And given your selection of wind power, your carbon footprint would not just be reduced but effectively eliminated.
Also, if you are heating only to 55, the radiators will be more effective with low temperature water than they are for heating to 72. The only problem is that once you have a low-environmental impact, low cost heating system, you might be inclined to increase the temperature closer to 72, so designing the heating system to be capable of that is a good idea, for you as well as your family and for future residents of the building.
First things first: It's premature to prescribe ANY sort of solution before getting a handle on the actual heat load that needs to be served, and we don't yet have enough information to make that estimate.
How many gallons, on which exact fill-up dates, in the December through March time frame?
What (if any) other information was next to the "Gallons corrected to 60.0F" on the slip? Was it a "gallons per heating degree day" number, using 60.0F as the base temperature?
If the burner is jetted to 0.75 gallons per hour the DOE output for the smaller get should be something like 90,000 BTU/hr- it can't be delivering 117,000 BTU/hr unless it has a ~1.0 gph jet. The 4-plate WMV-04 when jetted with a 0.95gph nozzle comes in at 117,000 BTU/hr (=117MBH ) of heating capacity, and 151,000 BTU/hr if jetted to 1.25 gph, according to the short sheet product ratings table about half-way down this page:
http://www.peerlessboilers.com/Products/ResidentialBoilers/SeriesWBVWV/tabid/118/Default.aspx#dnn_productratings
Are you sure it doesn't say 0.95. not 0.75?
With only one thermostat it has only one zone. If it's pumped hot water there should be a pump plumbed into on the system pipes, usually located near the boiler that turns on whenever you bump the thermostat up to call for more heat. There will also be an expansion tank on the system plumbing. If it's steam there will be no pump, no tank. A picture of the boiler that includes the near-boiler plumbing would make it obvious. The controls that come with the boiler differ in appearance too, between the steam version...
http://www.peerlessboilers.com/DesktopModules/Bring2mind/DMX/Download.aspx?EntryId=283&PortalId=0&DownloadMethod=attachment
and the hot water version...
http://www.peerlessboilers.com/DesktopModules/Bring2mind/DMX/Download.aspx?EntryId=284&PortalId=0&DownloadMethod=attachment
Figured out which one you have yet?
Is the 0.1299 /kwh the energy portion of the bill only, or does that involve the grid charges as well? (Divide the total bill $ by the total kwh used.)
The heat content of a cord hardwood runs in the 20 to 25 million BTUs depending on species, so for 1.5 cords you went through about 30-38,000,000 BTUs of wood. (The source fuel energy equivalent of about 225-275 gallons of oil.) The efficiency of wood stoves varies between 67% and 85% (in rare instances higher), but if you know the model number of your woodstove we can look that
ZIP code 19380 (West Chester PA) is in climate zone 4A, and has a 99% outside design temperature of about +14F. (Philly's is +15F, Reading's is +13F.)
Dana, the "corrected to 60 F" just means the gallon measurement is corrected for the expansion/contraction of the fuel oil at the temperature it was when it was delivered.
Thanks so much again, all. This is nothing short of AMAZING! Mr. Sullivan - 72 sounds like heaven!
Mr. Dorsett, I think it is the hot water version as there is a little box with pipes in the upper left quadrant. I'll try to attach a photo of my boiler. And you're right - it does say .95 not .75. I apologize.
For 2016, I only have three invoices in my file: 1/8, 3/10 and 6/19, and I can't find one for December, 2015, so I'll have to call my oil company.
And you were also right about the $.1299 not being the total. If I divide my latest bill ($179.83, thanks to my daughter liking A/C), by the kph (865) = $.20789. PECO lists "customer charge" $8.43, Distribution charges (@ $.06825), Ethical Electrical Charges Generation and Transmission @ $.1299. Somehow getting solar panels on my roof without cutting down old growth trees is looking better...
More information to come, and PECO is doing the energy audit September 9!
THANKS! Susan
Susan ,
What is your end goal or wishes ?
Once there is a bit of information maybe we could help you explore your options with realistic ideas that meet your wants and needs .
I will be in Devon tomorrow and again in a week or 2 , maybe I could take a look at the house and consult a bit , N/C for initials . Let me know
Thanks Richard! My end goal is to have a comfortable home in the winter that uses minimal fossil fuels.
Currently I am minimizing my oil use, but, as my son says, "There's a reason why they developed central heating." It takes a while for the wood stove to heat up the downstairs, and it doesn't reach the upstairs. If I have an electric space heater in my bedroom and want to get something from the kitchen, I'm cold for a while. It's not terrible, but it's not comfortable.
So what I'd really like is to use my radiators, but have them helped by some green source. I plan to renovate my kitchen, and in doing so, hope to have an architect or builder who can integrate green energy with my current oil fueled radiator system. For example, if there was a way of adding solar panels on the roof of my new kitchen addition that were able to boost the oil burner (now here I'm obviously showing my lack of knowledge about systems - but I'm speaking hypothetically!), that would be great.
Or if I could supplement with solar and continue to use my somewhat expensive, but green electricity (Wind powered) with some kind of a heat pump that was integrated into my oil system, that would be great.
I work, but am home on Fridays, and would love to talk to you! Best, Susan
Don't allow an architect or engineer tell you what you need . You'll do better using an integrated design and project delivery approach . Let guys who clean up after architects and engineers work it out as a team and send those professionals the details and assemblies . Feel free to contact me . [email protected]
Richard,
This constant bashing of other professionals and posturing as the only just man is getting a bit tiresome.
Susan,
Some GBA readers, including Richard McGrath, who (as far as I know) is a designer of hydronic heating systems, advocate in favor of fairly complex hydronic heating systems that require "an integrated design and project delivery approach."
Others, including me, advocate in favor of simple heating appliances that require a bare minimum of system design and no engineering. Examples of these appliances include ductless minisplits and simple space heaters.
No matter how you heat your house, it's a good idea to perform a heat loss calculation (for example, a Manual J calculation) as Dana Dorsett is urging you to do.
But before you take the plunge to invest in more heating equipment, take a deep breath. Remember, a hydronic heating system is just one possible approach.
Martin ,
I , as a rule only really comment on those discussions where one's requests include a hydronic solution . I also always as you may recognize , suggest a comprehensive room by room heat loss and careful consideration of the project along with an individuals wants and needs . I offer folks and potential clients free consultation which mostly includes measuring a building while within said building , in as much as that may be possible . Some are remote and plans must be used . A Manual J or ASHRAE Heat loss calc is always performed .
While hydronic systems certainly can be complex it is fairly well known that the IPDD approach is a good idea even when a hydronic system is not what is wanted or called for . The failures regularly experienced when there is no hydronic system are well documented . If they were not the number of GBA discussions would be far less and many experts including some GBA contributors would not have been able to study these failures and figure out what went wrong .
What you do not know is that many projects and owners receive the advice that a home or a strategy is not a good candidate for a hydronic solution and I recommend something other than .
Malcolm ,
I apologize if you take what I do as bashing . I assure you that is not my intent . My intent , as many GBA readers is to lessen others chances of receiving a crummy job because they trusted that a mans investment into a school of higher education in some way makes him the end all , be all . We call a man that passed Engineer whether he was at the top or bottom of the class . Many of these men do not really grasp what happens in the real world . I personally know men that specify mechanical systems but do not understand The Pump Affinity Laws , nothing could be worse than that when specifying equipment that will become an integral part of a system and in fact can be catastrophic from that point of view . I also believe that when one wants to explore an option that they be offered experienced professional help in that area .
I however do not posture as the only just man , just one that can help folks wanting to know about hydronic solutions from someone who you'd be hard pressed to find a negative story about after 30+ years of operation and designing in cooperation with some of the most well known folks in the HVAC and building performance industries .
Maybe you are an engineer , maybe you are very good at your job whatever it is . That is not however the rule but in fact is the exception .
Susan: Is natural gas available at your house? $2.79 per gallon of oil is insanely expensive, perhaps because oil heat is rare in your area. That price is about a dollar more per gallon than my neighbors in Maine are paying.
If you tighten up your envelope, switching to a gas boiler may be the cheapest alternative. It's still fossil fuel, but the money spent on air sealing, insulation or storm windows may mean you'll use a lot less fuel.
I wouldn't worry about using old growth trees. Firewood is typically produced from trees or parts of trees unsuitable for use as lumber. And in all likelihood, all the old growth lumber in your area was cut a very long time ago.
Yours is definitely a hydronic (pumped hot water) system. The big green cylinder over the boiler is the expansion tank, and there's a flexible conduit between the black circulation pump (on the plumbing on the right side of the picture) and the grey control box on the boiler itself. This gives you more and different options than if it were a steam system.
It also means that the radiators are sized for operation at a lower water temperature than 215-220F steam, and at least remotely possibly within the range of output temperature of heat pump solutions. But that would take a more detailed analysis. With more fuel use (and exact fill up dates, remember) it's possible to put an realistic upper bound on the whole-house heat load, and from there we can look at how much radiation you have per room to estimate the water temp requirements.
At ~21 cents/kwh an electric space heater is pretty expensive to operate compared to an oil boiler even at $2.79/gallon, which is more expensive than the $2.00-2.50/gallon seen in much of New England this past winter, but WELL below the recent 5-year average. Every kwh delivers 3412 BTU of heat into the house, so normalizing to dollars per million BTU (MMBTU) that's $0.21 x (1,000,000/3412) = $61.55/MMBTU.
A gallon of oil is good for at least 138,000 BTU/gallon source fuel energy (it varies- could be as high as 142,000 BTU/gallon) , and burned in an 85% efficiency in a boiler delivers 0.85 x 138,000= 117,300 BTU/gallon. Normalizing to MMBTU that's $2.79 x (1,000,000/117,300)= $23.79 /MMBTU.
For a lot of upfront money and a bunch of plumbing you COULD micro-zone the house and only heat the rooms you want, when you want using the radiators, but there may be better solutions, depending on how your load numbers work out.
In your location air source heat pumps can operate fairly efficiently if the water temperature requirements are under 110F (TBD), and would usually be much cheaper than ground source heat pump solutions up front, and would still beat the fossil burner on operating cost. But until we know more we don't really know if that's an option.
Ductless air-air systems can operate comparable or better efficiency (and they air condition at high efficiency) but we don't know if that's really a likely solution here either.
To beat oil on operating cost the seasonal average performance of an electric heat pump solution would have to be at least $61.55 / $23.79= 2.6 (HSPF = 8.9) or higher, which is a pretty reasonable expectation for optimally sized air source heat pumps in your not-so-severe climate. If you go for a larger amount of rooftop solar you'll likely be paying considerably less than 21 cents/kwh (on a lifecycle basis) for electricity too, especially after federal, state, & local subsidies are applied.
With the fuel-use numbers we can put an upper bound on the whole-house load, which may steer it one way or the other, but you really need the room-by-room load numbers before making a decision on the approaches for heating the whole house, or whether it makes sense to micro-zone it.
If you're in a rural area and have good access to cheap firewood an outdoor wood boiler MAY be another option, but there are some local air pollution issues to contend with when taking that approach too.
Wow! Again I'm amazed and dazed and impressed and in need of some note taking and research to figure all of this out!
Mr. McGrath, I certainly am wary of engineers or architects who don't understand these systems. Because I sure don't!
Mr. Sheehy, I'll check on natural gas. Yes, it's another fossil fuel! However, it may be more efficient?
Mr. Dorsett - Yay - we know it's hot water! I'll get those numbers on oil usage. When you say air source heat pumps, would that go through the radiators?
Dana makes very good points . I would suggest if possible using 2014 -15 fuel usage as opposed to 2015 -16 usage as last winter was very mild .
Most cast iron radiator systems were piped in a manner that would allow the use of TRVs at each radiator . This allows room by room zoning using simple wireless , mechanical thermostatic valves and improved comfort . It also allows for constant circulation and smaller equipment to be used and reduces short cycling .
Use any year's oil use you like, as long as it's wintertime usage only, and you have the EXACT dates. With your ZIP code we can look up the actual weather data, which is far more accurate than using the 25 year averages or some other WAG on the temperatures over those periods.
There are air source heat pumps with hot water output, but it's something a long shot. If you need water temperatures over 110F to get enough heat out of the radiators at the coldest outdoor that won't be a very efficient solution can be made to work. Most hot water systems need something like 130-160F water for the radiators to emit enough heat to keep the rooms above 68F at the 99% outside design temp (a code requirement), but if your heating system was originally steam and designed to heat the house with the windows open, you might have water temp requirements low enough. But like I said, that's a long shot.
If natural gas is available it's possible to run gas equipment much more efficiently using a condensing modulating boiler than with an oversized oil burner, and the operating cost is typically about half that of oil (but that varies widely with location.) Oil boilers need to run at much higher temperatures than condensing gas to avoid self-destruction from condensing it's highly acidic exhaust inside the boiler. Natural gas exhaust is also acidic, but much milder, mild enough that stainless steel can be used as the internal heat exchanger. The higher the operating temperature, the greater the proportion of heat that gets sent up the flue. The higher the mass and the larger the oversizing factor of the boilerl, the greater the standby loss. It's highly likely that swapping in a right-sized condensing gas boiler for your cast iron boiler would cost well under half the amount to operate, and put well under half the amount of carbon into the atmosphere, along with much lower amounts of unhealthy combustion by products, due to the simplicity of the molecular structure of the fuel compared to oil.
Propane is a similarly simple molelcule and also clean burning, somewhat higher carb than natural gas, but usually much higher cost than oil in $/MMBTU terms. But like natural gas, there are many condensing modulating boiler options for running the system at minimum operating temperature/maximum efficiency.
Hi Susan. You are getting great advice on the mechanical systems, but don't forget that the first step is improving your insulation and limiting leakage. With a tighter house, you can use a smaller gas boiler, for example. In the end, you can create a home that is more comfortable to live in while using less energy.
Yes, thank you Mr. Knapp, and I'm so grateful. And yes, I needed that push to get the PECO energy audit.
Mr. Dorsett, as much as I want a green house, I'm thinking that natural gas may be the way to go. Perhaps I can just trim my old trees shading my house enough to add solar panels for a new electric hot water heater (currently it's oil heated).
It's so kind of you to consider using past year winter oil consumption numbers, which I have for 2012/2013. This was before I got the wood stove, and before I kept the house so cold or used so many electric space heaters. I probably kept the house at around 65.
Let me know if I can do any of the leg work in researching temperatures or whatever. Here are my oil purchases for 2012/13:
December 10, 2012 - 233.1 gallons (@$3.579!)
January 4, 2013 - 236.3 gallons
January 16, 2013 - 95.7 gallons
January 26, 2013 - 115 gallons
February 8, 2013 - 112 gallons
March 14, 2013 - 83.3 gallons
April 2, 2013 - 95.2 gallons
Thank you AGAIN, Susan Hanway
So starting on 10 December 2011 on through 14 March 2013 you used.
236.3 + 95.7 + 115 + 112 + 83.3 = 642.2 gallons.
At 85% efficiency that 85% efficiency x 140,000 BTU/gallon x 0.85= 76.42 million BTUs (MMBTU) of heat delivered into the heating system.
If you kept the place at 65F on average, let's use 60F as the degree-day base. The degreedays.net website is currently having database access problems, so we'll have to wait to download the weather data. Hopefully they will have weatherstation data available that goes back that far. I'll dig around a bit, see if I can't find a similarly easy web source for that data.
---edited to add----
At much lower granularity (and bigger error than daily data) http://www.weatherdatadepot.com/? comes up with monthly base 60F HDD of:
Dec 2012----622 HDD
Jan 2013-----814 HDD
Feb 2013----778 HDD
Adds up to 2214 HDD
76.42 MMBTU / 2214 HDD is 34,517 BTU/ HDD
With 24 hours in a day that's 34,517 / 24= 1438 BTU per degree-hour.
Assuming a design temp of +14F and the base temp of 60F, thats 60F-14F= 46F heating degrees to keep it at 65F, but at a code-legal 68F that would have to be bumped to 49 heating degrees. The implied 99% heat load is then roughly
49F x 1438 BTU per degree-hour = 70, 462 BTU/hr, at +14F outside, +68F inside.
Call it 70.5K give or take 7K.
That's quite a heat load for a single air source heat pump to handle, but it's easy to find a modulating condensing gas boiler to handle that much load. But if the place is air-leaking and has little to no insulation it may be possible to cut 20-30 BTU/hr off that load, depending on the where-is-as-is state of the building.
I'm guessing it has no foundation insulation, which is usually easy & safe to retrofit into unfinished basements, pulling a good 10,000 BTU/hr or more off the load in most cases. Air sealing an old Victorian is sometimes difficult, but there may be another fairly easy 10K of load to shed there too.
How many square feet of house is this? Is the air usually super dry in winter, or do you get condensation on the windows a lot?
Dana is correct again . We must not forget though that probably 20% of your usage is water heating . Both the boiler and water heater also have terrible thermal efficiency and suffer great standby and stack losses . In other words loads are quite probably lower than stated above .
PECO gas rates and electric rates must also be examined to determine the true environmental and economical impacts on which is the BEST choice for Susan and Earth . This is true for a leaky house or a tight house . How is electricity generated by PECO in your area ?
A 90%+ AFUE high mass boiler capable of making high temp supply fluid yet allowing a large Delta T of say 40* ( perfect for cast iron emitters) could quite possibly condense , dependent on installed emitter oversizing (probable) for greater than 90% of a heating season . Due to the inherent low resistance these piping systems offer a single ECM circ can handle this easily ( 13 watts?) This same appliance could use 1 other similar ecm circ and a flat plate to offer an on demand DHW solution . These appliances also boast a 90% + thermal efficiency , very little energy lost up a flueway .
Your old boiler almost definitely short cycled for a great portion of the year making reaching a steady state 85% efficiency nearly a pipe dream and thermal losses taken into account bring the system efficiency down to a dismal 70% system efficiency in actuality . Would you agree Dana ?
I would totally agree that the standby losses make the 85% as-used efficiency probably a pipe dream, it might be close if it has the 0.95gph nozzle. With high mass radiation operated as a single zone it probably wasn't short-cycling itself into low efficiency, even if the duty cycle was lower than in an AFUE test. Standby losses to the basement aren't 100% lost, but if it isn't insulated more than half the standby loss is true loss. And if the boiler room is the warmest place in the house during cold weather, even the actual heat load is higher.
AFUE testing presumes 1.7x oversizing. If we take the ~70K number to be roughly the heat load, 1.7x 70K is 119,000 BTU/hr. So if the boiler is jetted with the 0.95 gph nozzle (= 117,000 BTU/hr output), the thing should (or could, if properly adjusted) come pretty close to hitting it's AFUE efficiency, but with the 1.25gph nozzle (151,000 BTU/hr output, more than 2x the load) it won't make more than 80% as-used AFUE. If it's jetted crazy-high with the 1.5gph nozzle (180K output, nearly 3x over) it'll probably struggle in at ~75%.
Look at system #1 in Table 3, p.9 (p14 in PDF pagination) :https://www.bnl.gov/isd/documents/41399.pdf
An 83.7% AFUE boiler with an embedded tankless coil performs at 74.9% as-used AFUE at 3x oversizing, but still makes 77.9% at fully 2x oversizing. At 1.7x oversizing it should hit pretty close to it's steady-state numbers unless it's truly short-cycling (= burn times shorter than 5 minutes, with more than 5 burns per hour.)
Unless you're filling a large spa tub daily, in the dead of winter the water heating will be less than 10% of the total fuel even though the annual fraction might be as high as 20%. But that hot water fuel use also offsets the (un-calculated) solar gains in the heat load calculation, which would otherwise skew the result to the low side of reality. These are the reasons why it's important to use ONLY wintertime data (low solar gain, higher fraction of the fuel use going toward space heating.
Still, the fuel-use type heat calculation is almost always an upper bound, and at ridiculous oversizing factors it can be quite a bit higher than reality.
If this boiler is going to see another heating season and is tuned up annually, it's worth making sure that it's the 0.95gph jet when the tech is there. Swapping in a new nozzle and re-adjusting the air/fuel mixture is part of the standard maintenance on an oil boiler, so it's not any more work to put in the smallest one, if it happens to be jetted with a larger one. If it's going to see a few heating seasons before something better gets swapped in it's worth adding a retrofit heat purging control too (eg. Intellicon 3250- there are others too) which will exercise the thermal mass of the system to advantage, lengthening burn times while reducing the number of burns, and lowering the average standby temperature for lower standby losses. If it's currently set up at 1.5gph the combination of smaller nozzle and heat purging controls would probably deliver a ~20% reduction in fuel use.
They're back up and running, but degreedays.net only looks back 36 months- they can't deliver a spreadsheet covering the winter of 2012-2013, but they do have data from the winter of 2013-2014, if you have wood + oil use for that season (or more recently) we'd be able to work from that. I'm not sure it really matters though- the order of magnitude of the load is pretty clear using the cruder monthly HDD data from Weather Data Depot.
Regarding the carbon footprint of PECO power generation, she's paying for 100% wind power (see response #14), and is planning to add solar PV on site. Any dirty power a heat pump would be using would be paid back with the greener stuff she's putting on the grid (or paying to have put on the grid.)
Thanks Again!
I'd really love to heat with something other than oil this winter, so I'd better get on it!
Mr. Dorsett, my house is 2,750 square feet in 3 floors. I don't have a spa tub, but more appropriate to the Victorian house, a claw foot tub which I love, but don't use daily.
In winter the air is not super dry and I do get condensation on the windows. I've already had a few windows replaced, and am getting a storm door for my enormous and leaky front door. There's also a storm door on the back door.
I do have a basement, and it is cooler than the rest of the house in winter. When the insulation guy came in he used spray foam in the basement and in the attic, but as mentioned earlier, he said he couldn't do the walls as there was not enough space. In the kitchen (added in the '80s), he said the walls were sheet metal (?).
For the winter of 13/14 I have the following:
11/30/13 - 81.6 gallons
12/17/13 - 95.9 gallons
1/16/14 - 180.7 gallons
2/4/14 - 167.9 gallons
2/28/14 - 170.2 gallons
3/20/14 - 123.2 gallons
I bought the wood stove in the summer of 2014, so it didn't affect the oil usage above
Mr. McGrath, I agree that the oil burner is not efficient, and want a MUCH better heating system.
I'm looking forward to the energy audit next Friday. Thanks AGAIN, Susan
The hot water is then likely to be well under 10% of the total fuel use.
The ~70,000 BTU/hr for 2750' of conditioned space from the previous fuel use calc is about 25 BTU/hr per square foot, which is on the high side for an insulated house or even a reasonably air tight house with no wall insulation, but could be real if that was before foam insulation was installed. (I'll re-run the numbers on the winter 2013-2014 data later, as time allows.)
I'm not sure what "not enough space" would mean, regarding insulating the walls. Can you describe the wall's construction in better detail?
Thank you for your response Mr. Dorsett,
There's about an inch and a half of plaster lathe, only an inch at the most away from the exterior brick! It's 1890 construction...
I was living alone that winter, and my kids only stayed over for Christmas break. Now that my daughter is living with me, the water use is MUCH higher...
This morning I noticed evidence of mice in my (cheaply added on) kitchen, and think that the kitchen may be a big part of the leakiness. Perhaps the front door as well. But I would love ideas about insulating the walls. I was thinking of putting cork or fabric on the walls of a front parlor that I want to use as a home office.
I hope you have a happy Labor Day, Susan
Thank you so much, again, Mr. Dorsett, for your time and expertise. I will try to figure out the bricks!
PECO is coming on Friday and will no doubt be delighted to also suggest gas... I very much appreciate the information on not buying too big a boiler and will read the blog on size, but would never have thought of that on my own. (clearly...)
Would it make sense to gut the interior plaster on just one room? A few winters ago one of my daughter/s friends left a window open (?) shortly before a very cold snap which broke a radiator, causing thousands of dollars of damage and leakage in the front parlor below. I have yet to repair it, as I don't use it, and the insurance company sent in workers who drilled lots of holes in that room.
Thank you again, Susan
Susan,
If your house has structural brick walls, you should read this article before you insulate the walls: Insulating Old Brick Buildings.
Don't be snookered by a contractor whom suggests the 100K boiler either citing domestic hot water demand . Many do that and it is not necessary in most circumstances . Using a 30 gallon IDWH and storing at 140* then mixing temps down offers 50 gallon performance even with the 80K boiler .
The only time that using the larger boiler would be acceptable is if there were a high DHW demand while not using an indirect storage tank but instead a Flat plate heat exchanger for DHW .
Most Victorians are not made of brick- many (most?) are wood framed buildings with wood siding. And, not all brick Victorians have structural brick. Of those with brick exteriors, many are balloon framed 2x4 construction with brick veneer siding, but (alas) not yours.
For the record, how many wythes of brick, &/or how thick is the wall? It's common to see 3-wythe brick of that vintage, but double wythe is also common, and even 4 wythe brick isn't unheard of on taller houses. The thicker the brick, the higher the thermal performance, so knowing the thickness would adjust expectations accordingly.
With your construction insulating the walls would require gutting the interior plaster & trim, or putting insulation and new siding on the exterior, either of which would be a fairly expensive and dramatic upgrade.
So, between 17 December 2013 and 19 March 2014 you used:
180.7 + 167.0 + 170.2 + 123.2 = 641.1 gallons of #2 oil
At roughly 85% efficiency that would deliver 140,000 x 0.85 x 641.1= 76.29 MMBTU into the heating system plumbing.
According to the weather data from KPAWESTC15 in Westtown Township (the nearest weather station with sufficeintly complete data for that period), there were 2774.1 heating degree days.
76.29 MMBTU/ 2774.1 HDD= 27,501 BTU/HDD
or /24=
1146 BTU per degree-hour.
Using the same 49F heating degrees from the cruder estimate done in repsponse #33, that becomes an implied heat load of
49F x 1146 BTU per degree-hour= 56,154 BTU/hr
That's considerably lower than the prior estimate, but at a ratio of ~20 BTU/hr per square foot conditioned space, a more credible number for the described construction.
So, when looking at a gas fired boiler, if you went with ASHRAE's recommended 1.4x sizing you'd be looking at a boiler with about 78,616 BTU/hr of output. Just about any manufacturer's gas boiler that takes 80,000 BTU/hr of fuel input at maximum fire would come pretty close, or at least close enough. Even at a non-condensing 87% efficiency, at maximum fire 80,000 BTU/hr x 0.87= 69,600 BTU/hr, which would be 1.24x oversizing.
At 1146 BTU per degree-hour you would be fully covered for 68F indoors all the way down to [ 68F - (69,600/1146)= ] +7F before it would even start to lose ground temperature-wise, fully 7F below the 99% outside design condition. With a wood stove as auxilliary heat to back it up you'd have huge margin in terms of total capacity.
There are several modulating condensing boilers out there that can fill the bill (eg: Navien NHB 80, HTP UFT-80W, Peerless PF80, Burnham ALP-80, etc), but it's important to not oversize the boiler, and go for a 100KBTU/hr version, especially if you are breaking it up into zones (which might be easy or hard, depending on the particulars.) For a discussion of those isse, see:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/sizing-modulating-condensing-boiler
[Edited to correct]
"At 1146 BTU per degree-hour you would be fully covered for 68F indoors all the way down to [ 68F - (69,600/1146)= ] +7F before it would even start to lose ground temperature-wise, fully 7F below the 99% outside design condition. "
Actually, the balance point, not the interior temp needs to be used for this calculation, so really you wouldn't use ground against a 68F interior temp until:
65F- (69,600/1146)= +4F outdoor temperatures.
But even that is likely to be a higher temp than reality. You'd probably be in negative single-digits before it would actually lose ground, since the 1146 BTU per degree-hour is an absolute upper bound based on an optimisically high as-used boiler efficiency.
[end edit]
Regarding insulating the walls of just one room, yes, it makes sense to do those upgrades when doing a major repair. Heat loss is a function of exterior surface area, R-value, and temperature difference. Any time a room's surface area can economically have it's performance raised (as when repairing a room's wall that has been damaged by water), that's the time to do it.
Regarding HOW that wall is best insulated, read Martin's linked to article. Note, your climate zone (4A) is fairly low-risk for freeze/thaw spalling, and if you have reasonable roof overhangs to limit direct wetting it's even better. The methods by which the floor joists are supported by the wall needs to be considered, but if you're not insulating below the subfloor or above the ceiling there aren't many serious risks here. But the more you can tell about the construction details, the better the advice will be.
Preserving the antique character of the window trim, kick boards & crown moldings may become an issue though, since the wall has to become thicker to insulate on the interior side.
Thanks so much Mr. Dorsett, I'm going to do that, AND I read Martin's article which was very helpful.
PECO came and gave me a lot of good ideas for insulating as well as showing how the contractor who spray foamed the attic and basement a few years ago neglected to air seal many areas, including the wall tops in the attic. He said I have balloon construction.
So I'm going to get new people in to try again! Apparently the attic was only insulated to about an R-19.
Much as I wanted to be green, apparently Ethical Energy, my supposed "Wind power" supplier, is controversial. I have to look into them.
Next time I buy a house I'm going to pay attention to the trees, as my 3 big old trees prevent me from going solar, although I am going to have a supplier come out to see if it's worth trimming them so that I can add solar panels.
So I'm going to convert to a gas boiler, and heed your warnings about not getting one that's too big. I'll be back in touch with questions about that, I'm sure!
THANK YOU ALL! Best wishes, Susan
If you hate using those fossil fuels Susan I suggest getting someone who is good at keeping the boiler off as much as possible while still keeping you comfortable . Take a look at Heatinghelp.com to identify someone in your area . If I can help you not get fooled by paid advertisers look me up 08755
Unfortunately PA legislators & utility regulations don't (yet) have a mechanism for those with unfavorable shade factors to buy into community solar developments and have it "virtually net metered" just as if it were located on your side of the meter on your house. That's possible in a handful of states now, the details of which vary a bit. That may eventually be possible, but not today.
From your prior description of the walls it did not sound like balloon framing, but rather structural brick walls with furring on the interior side onto which the lath & plaster was attached. Is part of the house brick-veneer with structural wood framing, and other parts structural brick, no structural studs?
Or, is it the case that it is just the partition walls between rooms are all open topped into the attic?
Thank you Mr. McGrath, I'll check that out after returning from vacation in October.
Mr. Dorsett, I'll write to my state legislator. Regarding my walls, there is an inch or so between the brick and the lath & plaster. I don't think part of the house is brick-veneer. Yes, I think the partition walls are all open topped into the attic and will ask the auditor.
How do I find the greenest electrical supplier if Ethical Electricity is indeed not wind powered?
And regarding a gas powered boiler, any brands you like best or should I look for the highest efficiency?
Thanks again, Susan
HTP or Lochinvar are the clear leaders Susan
Thanks Mr. McGrath!
And Mr. Dorsett, here is the response I got from the energy auditor:
Great to hear from you!
I would have to agree. I think that you have furring strips with lathe and plaster. I have seen several homes over the years that customers have removed the plaster and studded out the walls to do an r13 in the cavities. This is a ton of work.
As far as the interior walls, they were open at the top and should be air sealed.
The efficiency of any boiler is easily undercut by a bad implementation. It's really about finding the right installer. There are many decent boilers.
If you're running it as a single zone rather than breaking it into multiple zones the turn-down ratio of the boiler doesn't much matter, but if it's smalller zones something with a minimum fire input less than 10,000 BTU/hr is preferred.
Fire tube heat exchanger type boilers tolarate a wide range of pumping rates can almost always be pumped direct, without a separate pump and loop to guarantee the required minimum flow at the boiler. (This is refered to as "primary/secondary" piping.) Going on Richard's short list,Lochinvar is probably still demanding that additional loop- in the past they have voided the warranty if it wasn't included. For their (relatively inexpensive) UFT series fire tube boilers HTP makes a marketing point out of the fact that primary/secondary plumbing isn't necessary, which simplifies the installation, and it would usually be an easy drop-in replacement on systems previously running on a cast iron boiler. That's probably the best bang/buck for a drop-in, with minimal or no zoning changes.
But the UFT-80W previously mentioned will also modulate down to 8000 BTU/hr in, which means you could break it up into more zones if that was desirable. Of course there's a lot more plumbing and design work to break it up into zones, which will then cost more.
I'm not sure how third party electricity suppliers work in PA compared to other places, or what the rules/markets are. What is the controversy surrounding Ethical Energy?
Dana is correct about designer / installers .
Dana ,
KHN model has direct piping capability as per manufacturer . Everyone should always remember however system design and other factors may prevent possibility of direct piping even though manufacturer states Pri / Sec not required .
Thanks for the tip on the KHN series (another low fire tube design, the wave if the future?!)
The KH-085 is probably the right fit, unless she can reduce the heat load a bit more.
Thanks Mr. Dorsett, breaking it into zones seems the most energy efficient when there's no one on the third floor, or when I have my wood stove cranking and the downstairs is 80 degrees.
Thank you for the technical information. There's a local supplier called Oliver whom the previous owners used to put in the central air, and they come highly recommended by both PECO and an independent reviewer.
As to the controversy surrounding Ethical Energy, I'm struggling to find what my PECO energy auditor described through extensive googling, and plan to call them. There was a complaint on a "rip-off" site about the fact that their rates started out low and shot up - but that's what can happen when you choose a variable rather than a fixed rate. My auditor said that they claim to use 100% wind but actually, what I get is a mix of "clean and dirty" electrical sources. However, this is how the New York Times explains it:
Signing up for the service, however, does not mean that the energy flowing into a household or office building actually comes from a specific source; rather, the promise is that the money customers spend will go to support renewable power plants rather than conventional ones. The service companies do this by buying electricity on the wholesale market from clean sources to match the use levels of their customers. That adds renewable energy to the grid over all, theoretically reducing the use of fossil fuels and helping to increase the development of alternative sources by providing revenue for the generators.
The PECO auditor suggested that their electricity was not all from clean sources - that's what I want to find out. However, it sounds like a systemic problem rather than a slimy business.
Be very careful of Utility recommended contractors and reviews Susan . The lack of REAL KNOWLEDGE about all types of systems for heating and A/C is rampant . Those recommendations are self serving to the Utility and anyone whom has a heating system installed who is not freezing and saw a modest fuel usage savings will give a good review . Just like the building assemblies discussed here as opposed to what folks received from their recommended local BEST guy , we can do better , most times , MUCH BETTER . I know men in your area that can design and do the job you're really looking for . My offer to assist you in protecting yourself still stands .
Your old cast iron radiators present a very real opportunity to go many different ways dependent upon heat loss calcs , your wishes , oversizing of those rads (likely) , zoning . Finding someone who knows what to do with them in concert with an efficient source is the challenge .
Thank you again, and Yes, I am learning a LOT! In fairness to the PECO auditor, he said he was not supposed to make any recommendations, and does not use PECO electricity himself. However, he did give incorrect information (which he got from a local tv news network) on Ethical Electricity.
Mr. McGrath, Are you suggesting that I not go with gas? It seemed that the consensus was that geothermal didn't make sense given the load my house is currently carrying. And although the auditor provided good advice about going back to the attic and basement, caulking the windows, etc., Mr. Holladay's wonderful article on brick walls made me realize how limited my options are on insulating the walls - short of spending a LOT of money....
I am not suggesting not going with gas . Nobody should suggest anything without having all the tools to do so . Room by Room heat loss calcs , infiltration numbers , radiation survey and an in depth client interview to determine how he / she and their family live in the home and what and where exactly it is that they want to get to when it comes to fuel usage , budget and whether those things all line up .
If you'd like , I will be in your general area , Wednesday through Friday and may have the opportunity to discuss your project . If you'd like you can send me your contact information .
[email protected]
Third party retail electricity brokers usually offer different mixes of power (50% renewables, 100% wind, etc) at different pricing points. While they can't guarantee the instantaneous power going into your house had the mix you signed up for, in most states by law or regulation they have to purchase the amount & type of power you signed up for in the aggregate over some reasonable period of time, so that on average it matches. These contracts are outside of and in addition any state mandated renewable power that the utilities might be required to purchase to meet any Renewable Portfolio Standard targets, etc. So, when you sign up for renewables through a broker such as Ethical Energy, it really is an addition to the total fraction of renewables going onto the grid.
Micro-zoning with thermostatic radiator valves is a realistic possibility here, but hydronic heating design at that level of detail isn't amenable to a "design by web forum" approach.
Air sealing the partition wall stud bays at the top and other air sealing at the attic floor plane can have a pretty dramatic effect on the total infiltration draw. The is PARTICULARLY true for a three-story house with the high ceilings common in Victorian era homes, with more than 3x the "stack effect" drive of a slab-on-grade ranch house.
Mr. McGrath, I am in Cape Cod this week but am interested in having a better understanding of how you would help the insulation process. Currently I am planning to have a local heating and air conditioning contractor who is highly rated on two different rating sites (like Angie's list) doing the gas boiler installation. First I would meet with them and see whether they know about micro-zoning with trv's.
Mr. Dorsett, thank you - that's what I thought about Ethical Energy, and it's good to know that the air sealing will be helpful.
Hello again wonderful advisors. Progress and new questions:
The Oliver (local heating co.) came over and after I told him that I was willing to pay more for high efficiency, recommended a boiler made by a Bosch subsidiary - Buderus, which he said was direct vent and modulating. What do you think?
On another subject, I talked to several people about insulating the front parlor room where I have to do some work anyway due to flooding. You might recall that I have only about an inch between the brick and the wall, and your recommendation was to tear out the walls and rebuild out, with enough space to put in insulation. However, I've realized that there are pipes on the outside of the wall (I think because they took out a radiator in front of the front window) as well as a radiator against another wall. In addition,
in front of the window where they took out the radiator, on the exterior, is not brick, but vinyl, which has been insulated. A picture or two would be helpful here, I know! To make a long story short, I'm wondering whether there's a way to insulate inside that room, but on top of the wall rather than inside. Foam board? My old idea about padded fabric? Cork? Do I make any sense?
Thanks again, Susan
Susan,
Your question is unclear.
There are three basic ways to insulate a wall in an existing house.
1. If there are studs -- usually 2x4s that are 3.5 inches deep, or 2x6s that are 5.5 inches deep -- you can install insulation between the studs. It's unclear whether your vinyl-sided wall has studs, but it probably does. The wall that is made of structural brick has no studs.
2. Option Two is to install insulation on the interior side of the wall. This might mean a continuous layer of rigid foam, followed by drywall, or it might mean new studs filled with insulation.
3. Option Three is to install insulation on the exterior side of the wall. This usually means a continuous layer of rigid foam, followed by new siding.
Buderus is a quality manufacturer, but the modulation range is only about 3:1 for the smaller oned ( GB142 series) The smallest is the GB142/24, which only modulates down to ~25,000 BTU/hr out at minimum fire in condensing mode, ~75,000 BTU/hr out at high fire in non-condensing mode.
Your design temperature load based on fuel use is about 55,000 BTU/hr, so as long as you don't insulate and air seal the place TOO well the GB142/24, would both cover the load and modulate reasonably well. But with the planned improvements it's likely that your design load will drop well under 50,000 BTU/hr, which would make it less than ideal, only modulating during the colder weather, cycling (but not short-cyclnig) most of the season due to it's limited modulation range.
Under no circumstances should you leat them install the next size up, the GB142/30, which has a minimum modulated output of ~30,000 BTU/hr, which is over half the load of the "before thermal upgrades" version of your house.
The Bosch Greenstar 57 may cover your "after" picture design load just fine, and modulates down to about ~12K-out, but it's marginal at the high end for the "before" picture. The Greenstar 79 would be roughly equivalent to the GB142/24 for output & modulation range. It would cover the peak load with a lot of margin, but only modulates down to ~22K-out (lower would be better.) With a more accurate heat load calculation to know with confidence it will cover the 99% heat load with some margin, the Greenstar 57 would be the better choice.
Thanks Mr. Holladay,
It's been a while since I wrote, so I assumed you might remember! There's only about an inch between the lathe and the brick in my 1890 Victorian. Mr. Dorsett recommended that I might tear out the walls (already damaged) and therefore be able to put in insulation and build a new interior wall out farther into the room.
Susan,
Dana Dorsett is right, of course. You can build a 2x4 wall on the interior side of your existing wall if you want, and you can insulate that new 2x4 wall.
In Comment #59, you asked, "I'm wondering whether there's a way to insulate inside that room, but on top of the wall rather than inside."
I'm not sure what you meant by "on top." I thought you might mean, "on the exterior side" -- which explains why I provided the answer in my Comment #60.
Frankly, your question still confuses me. If you want to take Dana's suggestion to build a new interior 2x4 wall, I guess you are all set.
If you were trying to say something else -- perhaps you were wondering whether you can install a continuous layer of interior rigid foam without installing a new 2x4 wall -- the answer is yes, as I already noted in the answer in my Comment #60.
Mr. Holladay,
I didn't mean to post that last time - I was trying to include a photo and while fooling around, it posted. By "on top" I mean on the surface of the interior wall, so that I don't have to rip out the walls.
There are three reasons I don't want to rip out the interior walls, besides the obvious - cost and mess. 1) existing pipes (hope the photo works), 2. radiator, 3. outside of that room is not all brick (I read your article, and as I live near Philly am not so worried about insulating) but they for some reason added vinyl to a portion of the exterior wall which is insulated. So in my mind that lessens the need for insulating that room, in addition to 1. and 2. (oh, and #4. is existing moldings and 5 large windows in that room).
And here are the interior pipes - right near the wall...
Susan,
As I noted in Comments #60 and #63, you can install a continuous layer of rigid foam on the interior side of your wall, followed by new drywall, if you want. Here is a link to an article that discusses this approach: Walls With Interior Rigid Foam.
It's also possible to hire a plumber to move a radiator or relocate your pipes. Plumbers do that kind of work all the time.
Thanks Mr. Holladay,
So you're saying I can't put anything ON THE SURFACE of the interior wall? It seems like a LOT of work for LITTLE reward to rip out walls when part of the walls are covered by insulated vinyl, as mentioned. I am really not trying to tax your patience - I just want a definitive answer.
Mr. Dorsett, As mentioned I sent the boiler installer your calculations for the heat load. Perhaps he doesn't recognize that I used a wood stove a lot and also had the heat turned down low - I'll e-mail him to make sure he got that. Currently he is adamant that a 100,000 btu boiler is required, as below:
Hi Susan-
I've been doing this for 24 years and I pride myself on my knowledge and I respectfully disagree with these folks.
They may be great at insulating but their load calculation isn't even close. There is no considerations made for pipe loss in basement nor have they said one thing about flow rate with the large cast iron mains that your home has.
You have a load over 100,000 btu unless you are doing something like spray foam insulation which is not feasible.
I would recommend you let them handle weatherization and have an HVAC contractor like us handle the boiler. I am very against oversizing and always err on the side of undersizing. That being said, if I put a boiler in that small you will have issues with maintaining temperature.
Thanks,
Dan
Dan Lippin
Regional Project Manager
Good morning Susan-
Attached is my full, detailed, industry approved Manual J load calculation.
This calculation takes into account construction/insulation, square footage, and hot water piping.
As predicted, my calculation calls for much more heat than the green building folks have called for.
I will get my proposal out to your shortly.
Thanks,
Dan
Susan,
I'm not sure why my answers are confusing you. I wrote, "you can install a continuous layer of rigid foam on the interior side of your wall."
The rigid foam can be installed on the interior side of the existing plaster, using cap nails or adhesive.
I'm not saying that you should do this. I'm saying that if you want to insulate your wall, that's one way to do it. But you don't have to if you don't want to.
Susan: The pipe losses to the basement are already included in a fuel use heat load analysis, and need not be considered separately. In fact, there is no way to even separate those losses out! The beauty of a fuel use load analysis is that it's completely agnostic about the condition of the house or the condition of the heating system. We only have the source fuel BTUs, the nameplate efficiency of the boiler, and the weather data to work with. We don't know of half the output heat was lost to the basement, or if it was only 10%, and it doesn't really matter.
If you were using the wood stove extensively, how many cords of wood, do you use in a year and what is the published efficiency of the woodstove (if you have it)
Extrapolating the load from fuel use to come up with the load at a code-min 68F based on some lower thermostat setting isn't rocket science. Reading over the calculations back in response # 33, your information in #32 that you had kept it at 65F indoors on average. The extrapolated load base on that information up with a design load of ~70,000 BTU/hr, give or take 10%, then was later corrected when better information was available in response #39, to about 56,000 BTU/hr.
Unless you went through 5-10 cords of wood that year &/or had actually kept the thermostat at 50F instead of 65F, the notion that your load is over 100K is simply not credible, since that would imply a boiler efficiency considerably greater than 100%. (An aging oil-boiler's true efficiency is going to be under the 85% assumed in the calculation.) The true efficiency is always lower than nameplate efficiency, which means the true load (including basement losses) is in all likelihood under 56,000 BTU/hr, and that is including the pipe losses to the basement.
At that is before your current ongoing retrofit air sealing & insulation which will pare that down incrementally.
The flow rate in the distribution plumbing can be managed by primary/secondary piping of the boiler if need be. In most retrofits that isn't necessary if you use a fire-tube heat exchanger boiler, but yours could be one of the exceptions that proves the rule. You don't need to install a larger boiler to deal with what is achievable with hydraulic separation between boiler flows & system flows.
The full Manual-J would be a useful document to review, if you can attach it. Nearly all boiler installers & HVAC companies have an inherent bias toward using ultra-conservative assumptions in a Manual-J shooting to the high side (to avoid the 5AM call from the shivering irate customer- it's only human nature). But a fuel use calculation is better than a Manual-J, it's a MEASUREMENT, using the old boiler as the measuring instrument.
Assuming that the old equipment really still operates at it's nameplate efficiency is also shooting to the high side, but there are fewer places to have a thumb on the scale to bias the numbers in a fuel use calculation. HVAC companies nearly always use much higher than reality air infiltration numbers, and they often underestimate window performance, and (even more egregiously) use outside design temperatures 10F or more colder than the 99th percentile temperature bin, and warmer than code-min 68F indoor design temperatures. These errors add up fast, but are easily neutralized by fuel use load estimates. Most of those thumbs can be spotted in the Manual-J, some of which are simple to correct with out re-running the program.
With all due respect to the 24 years of experience, you can't get more out of the boiler than the BTUs of the fuel that went into it, but that's what the contractor's assertions really imply.
Dear Mr. Holladay,:
I think our communication issue has to do with my wishfulness about being able to insulate from the exterior surface of the interior wall, and due to your "closeness to the material." It is probably patently obvious to you that I can't do so. I am looking for explanation or ideas about how to do so.
Mr. Dorsett: Thank you. I am attaching the Manual-J. Perhaps I misled you by saying that I kept the house at 65 degrees last winter. I did not. During the day I had the thermostat at 50. When I came home from work I turned it up to 60, lit a fire, and went up to change in my bedroom, using the electric heater to warm my room to 70. By the time I came down to make dinner (using an electric heater in the kitchen), the wood stove was starting to put out heat. Soon it would override the thermostat - just around the corner. I'll try to find the efficiency of the wood stove. Thanks again, Susan
Also, Mr. Dorsett, I went through a cord and a half last winter.
Here is the latest from the boiler installer:
Hi Susan-
Thanks for the feedback. I did not mean to say that I thought you saw me as unqualified-I was saying that my means of coming up with the sizing of the boiler was the way to go.
My design load (industry standard) is based off of:
House square footage, house construction materials/windows/doors and amount of heat (Btu’s) needed at ACCA (Air Conditioning Contractors of America) sizing guideline of 14-degrees.
This program takes into consideration pipe loss in basement as well.
I unfortunately have to size equipment for the load of the house and the possibility that you could sell the house someday. If I size it assuming that the heat is kept at 60-degrees the load will be wrong for the standard design temperature of 68-degrees.
Sizing based on historical data, fuel usage, fuel pricing is not prudent as all of those are subject to change. Constants that the boiler sizing are predicated upon are all those I have noted above
I have zero doubt that these folks are great at all things involved with weatherization and greening your home but I do not feel comfortable with their sizing of the boiler.
I’ll get that proposal out to you ASAP.
Thanks again.
Dan
Susan,
I'm still struggling. You want to "be able to insulate from the exterior surface of the interior wall." What material are you talking about?
I thought you were talking about insulating on the interior side of the plaster -- but now I'm lost again.
The interior wall means... furring strips? Studs? Plaster? Something else?
Once we figure out what you mean by the "interior wall," we need to determine what you mean by "the exterior surface of the interior wall."
"Perhaps I misled you by saying that I kept the house at 65 degrees last winter. I did not. During the day I had the thermostat at 50. When I came home from work I turned it up to 60, lit a fire, and went up to change in my bedroom, using the electric heater to warm my room to 70."
Garbage in= garbage out. If we don't have the true thermostat settings there is no way to calculate the load from fuel use.
Since you kept it at 50F, but ramped up to something warmer for several hours per day, set's try it using base 50F (perhaps more appropriate for the use cycles described) rather than 60F.
From the prior fuel-use analysis in response #39:
------------
So, between 17 December 2013 and 19 March 2014 you used:
180.7 + 167.0 + 170.2 + 123.2 = 641.1 gallons of #2 oil
At roughly 85% efficiency that would deliver 140,000 x 0.85 x 641.1= 76.29 MMBTU into the heating system plumbing.
------------
Using base 50F the http://www.degreedays.net/# data set for weather station KPAWESTC15 comes up with 1875.2 HDD50 for 17 December through 18 March, and 1862.5 HDD50 for 18 December through 19 March, so for slightly better accuracy we should average them, since the partial day differences on 17 December and 19 March clearly differs. That works out to 1869 as the most likely HDD average for that much fuel use.
76,290,000 BTU/1869 HDD= 40,819 BTU/HDD
/20 hours in a day becomes 1701 BTU/degree hour.
The outdoor design temp is +15F (per the Manual-J, which is a credible number for that location), and assuming a 68F code-min indoor temp the balance point will be about 65F, for a total of (65F-15F=) 50 heating degrees. The implied load is then
50F x 1701 BTU/degree hour= 85,050 BTU/hr
That is quite a bit more than the previously estimated 56,154 BTU/hr, but it's still well under 100,000 BTU/hr.
The 2.5 cords of wood has about 40-45MMBTU of source fuel energy, but in an unrated EPA -legal wood stove you can't assume more than 67% average efficiency. so you're looking at another 30 MMBTU of heat input, but at a warmer room temperature. Using the base 60F numbers from response #39, it came up with 2774 HDD60. The 30,000,000 BTU/ 2774 = 10,815 BTU/HDD, which is 451 BTU/degree-hour. With 50 heating degrees that adds another 451 x 50= 22,550 BTU/hr to the load number.
Add them together and you're at 107,600 BTU/hr, which implies an insanely leaky house or a lot of single pane glass.
And it's 14% higher than the 94,194 BTU/hr calculated in the Manual-J, which could be a function of intentional overestimating the efficiency of the boiler (likely) or overestimating the true net efficiency of the woodstove (also likely).
There is also a great deal of squish in the infiltration numbers, which may have been even higher than the fairly high estimate they used (372 cfm worth 22,498 BTU/hr of heat load). Even the 94,194 BTU/hr heat load number is high for 2750' house, even at low insulation levels (that's nearly 35 BTU/hr per square foot, whereas 20-25 BTU would be a pretty common ratio.)
The Manual-J report attached was only the 2-page synopsis, and does not cover the room by room loads, or the U-factors used, so there's no way to estimate the credibility of those details. To their credit they didn't use an insanely low outside design temp such as +5F or 0F, and they only bumped the indoor design temp by 2F above code-min. If the 1.5 cords of wood and 50F thermostat setpoint are accurate, the Manual-J and fuel use analysis are in reasonably close agreement, since the older boiler is probably closer to 75% efficient as-used. (Assuming 85% efficiency is intended to deliver a firm upper-bound.)
It would not be difficult to improve the infiltration numbers considerably, and even very modest amounts of wall insulation would make big dent in the 31,000 BTU/hr of calculated wall losses.
With blower-door directed air sealing the 22,498 BTU/hr of infiltration loss can be cut in half (probably more than half) peeling more than 10,000 BTU/hr off the heat load. That brings the 94K down to under 84K.
At a 50F delta the 31,062 BTU/hr loss for 2911 square feet of wall works out to about U0.21, which is less than R5. Even half-inch of foil-faced polyiso behind the wall board with a 1/4" air gap to the brick on the interior side of the wall behind half-inch wallboard would roughly cut that number nearly in half (at least for the rooms where you're gutting the wall), without making the wall dramatically thicker (if at all.) For the square feet of wall that you gut & treat that way, reduce the calculated load by 4 BTU per square foot (eg: If you have a 12' x 9' section of wall that you gut and install 1/2" polyiso + 1/2"gypsum board, that's 108 square feet, so subtract 432 BTU/hr from the calculated load.)
The 6272 BTU/hr of floor losses over the ~1200' of crawl space can probably be reduced to under 500 BTU/hr with 3.5" of fluff between the joists and an inch of foil faced polyiso cap-nailed to the bottom of the joists. That's a pretty easy 5K+ of load reduction
So if you modestly insulate 200-300 square feet of wall, insulate the crawlspace floor and do some real air sealing you'd already be down in the 75-78K range.
Insulating exterior walls in unfinished parts of the basement can be easy-pickings, and sealing up the old flue (and chimney chase) for the oil boiler will reduce the whole house infiltration drive, so there's room to save on the whopping 18,000 BTU/hr of pipe losses to the basement. If most of the basement can be sealed & insulated those pipe losses are no longer totally lost- most of those BTUs accrue to the heat load of the first floor by keeping the floors warmer.
Wow! I think I'm driving you both insane - and not in a good way...
Mr. Holladay, By interior walls I mean inside the house. By doing something to the surface of the interior walls I mean putting something on top of the walls inside the house. For example, I often see, in design magazines, people putting fabric on top of the walls instead of wallpaper, and sometimes it's padded fabric. Is that for insulation? What about cork? What about putting that rigid foam on the outside of the wall, LIKE PAINT. Inside the house. And then painting it or wallpapering or whatever. Does that make sense?
Mr. Dorsett - Wow! And to further complicate matters, I forgot to say that I turned up the heat on the weekend to a whopping 65! But that only adds to your belief that I don't need a 100,000 BTU boiler. Thank you! I'll let you know what I hear back...
Susan,
"Exterior" means towards the outdoors.
"Interior" means indoors.
"The exterior surface of the wall" is either vinyl siding or brick.
"The interior surface of the wall" is plaster.
When you wrote, "exterior surface of the interior wall," I'm pretty sure that you meant to write, "the interior surface of the exterior wall." You've been talking about the plaster, not the vinyl siding, although you are using the wrong word to describe the surface.
Read my answer #68 again. Yes, you can add insulation to the interior side of your wall.
I may have over stated the performance improvement with just 1/2" of polyiso, since the Manual-J indicates:
" Wall-Frame, no insulation in stud cavity, R-2 board insulation, brick finish, wood studs"
That doesn't quite match the furring w/plaster & lath on brick stackup described in this thread. If the plaster & lath are about an inch thick (combined) as is often the case with antique horsehair plaster, that layer is worth about R1. The 1" air gap is also worth another R1. At ~6" thickness the brick would be good for about R1.2, at 8" about R1.6, and the exterior + interior air films add another R1. So fudging the brick at R1.5 , you have about R4.5 total, or U0.22, which is pretty close to the U-factor used in the Manual-J, which is probably why the contractor picked it, even if the description wasn't quite to a tee.
If you rip out the plaster & lath and replace it with half-inch gypsum and half-inch polyiso you'd have about R3.5 in the replacement layer, and you'd still have the R2 of air-films (including the gap) and the R1.5 of brick for a total of about R7, or a U-factor of U0.14. That's only about a 1/3 reduction in wall loss, not half.
If the gap is currently about an inch (as described in response #62) it's fine to reduce the gap to as little as 1/4", which gives you room for a bit more polyiso, and much bigger improvements. A full inch of polyiso + 1/2" gypsum replacing the plaster & lath and part of the air channel would cut the wall losses by fully half (or a bit more), and would leave a nominal half-inch of air gap, without losing any interior space.
To bring it fully up to current IRC 2015 performance would require a U-factor of U0.060, or about R16.7 "whole-wall". With R2.5 of air films & brick, and R 0.5 of wallboard that means the continuous foam layer would have to be R13.5, so you'd be looking at 2.5-3" of foam, losing a couple inches of interior space. But that would take more than 70% off the wall loss figures. (If you gutted & insulated with 2.5- 3" of foam everywhere the ~31,000 BTU/hr of wall loss then becomes ~9000 BTU/hr, reducing the heat load by more than 20,000 BTU/hr.)
Hello again Mr. Holladay:
Thank you for the terminology. I did mean exterior surface of the interior wall - as I wrote, "Think Paint". What I'm saying is that it feels like a whimper for a very few bucks to rip out the walls of that room and insulate on the inside of the interior wall. What I'm asking, therefore, is what can I do on top of the wall (think paint!) such as cork, padded fabric, special wallpaper, etc.
In #4 Mr. Knapp said it would be a waste of money. I'm doubling back because it feels, intuitively, like a good idea. Of course, I shouldn't be trusting my intuition and asking advice from you. I'm double checking.
Mr. Dorsett: My highly rated local supplier (Oliver) is drawing a line in the sand and saying they won't go less than 100,000 BTUs. I'm going to read what you've written and what he's written, take notes, and try to figure out what I don't understand. Below is another explanation as to where he's coming from:
Hi Susan-
I had my house spray foam insulated and air sealed, I have the highest efficiency heat pump ever made, and I am one to conserve whenever possible.
I did a job 5 years ago for a gentleman in Landenberg by the name of Levin Claus. It was a geothermal install in an old farmhouse.
I quoted a 5-ton geo and he had 3 other companies quote a 3-ton geo He said all things being equal that he wanted to go with us but wanted the smaller system. I wanted/needed the job badly enough that I downsized the equipment based on the sizing of others and installed the 3-ton unit.
3 months after we started the installation, we went back to completely reinstall everything. We ripped out the undersized 3-ton unit, installed the 5-ton unit that I had recommended, had our well driller come back and upsize the loop, and we ripped out all the brand new ductwork and replaced it with ductwork sized for 5-tons.
If not for my very good track record at Oliver I would have been terminated as the redux cost us $15000+ that we did not go back to the customer for.
The 5-ton unit has worked perfectly.
That being said, If you wish to have to a small boiler installed as these folks are outlining I unfortunately will have to decline the invitation to bid. Your home at minimum needs 100,000 Btu output. I cannot expose Oliver to the type of nightmare that occurred at the Claus residence.
I would love to do the job for you but I just can't grossly undersized a boiler in a very old home that is almost 3000 square feet.
Susan,
I give up.
Look at the drawing. The drawing has labels. (Click on the drawing to make it bigger.)
.
https://www.youtube.com/watch?v=jc_oLZuFwaI
Susan: You have the contractor in the position of being defensive, but like nearly all contractors he's much more concerned about undersizing than oversizing, for the reasons outlined in his geothermal heat pump example. With geo the cost delta is huge, as is the replacement cost, which makes the client very unhappy when they get it wrong in either direction.
With a gas boiler undersized even 25% in capacity the house would never drop to the 50F temps you have been running, and with a wood stove as auxilliary heat you would be able to keep the place at 70F even on the coldest hours of the coldest nights with a 25% undersized boiler. What you would NOT be able to do with an undersized boiler is let it drop to 50F then ramp it back up to 70F quickly, but that's not how a modulating condensing boiler is normally operated.
When contractors dig in their heels and draw lines in the sand I'm usually inclined to look elsewhere. YMMV.
If you want to respect the line in the sand and put in a bid for a 100K boiler, insist that it's minimum modulated output be no higher than 20,000 BTU/hr (which rules out the Buderus 142/30), since you want a boiler that modulates most of the season even AFTER improving the thermal performance of the place. These boilers are not the things of fantasy- they definitely exist:
HTP's UFT-120W delivers more than 105,000 BTU/hr at high fire at non-condensing temperatures, yet can modulate down to about 11,500 BTU/hr in condensing mode. http://www.htproducts.com/literature/UFT-brochure.pdf
NTI's Trinity TX151 delivers over 130,000 BTU/hr at high fire at non-condensing temperatures, and can modulate down to about 18,000 BTU/hr out in condensing mode: http://www.ntiboilers.com/uploads/nti/pdfs/sales/NTI_Bro_Trinity_Tx_SB_HR_Sept2016.pdf
Lochinvar's KH-155 puts out over 140,000 BTU/hr at high fire, yet can modulate down to under 15,000 BTU/hr in condensing mode.
There are others- let them pick one they're willing to support, but don't settle for something that can't ramp low enough. Make an absolute maximum of 20,000 BTU/hr for the min-fire output YOUR line in the sand. :-)
If you insulate the basement, get serious about air sealing and install insulation where its easy or more cost effective, your heat load will be under 70K, maybe even 60K. Say with diligence over a few years time you pare the load down to 70,000 BTU/hr. Using a crude linear approximation (which is close enough to make the point), with a load of 70,000 BTU/hr at 70F indoors, 15F outdors, that's at a difference of 55F. So the load grows by about (70K/55F=) ~1273 BTU/hr for every degree below 70F. The output of the GB142/30 doesn't go below 30,000 BTU/hr, so the outdoor temp at which it stops modulating and only cycles is ( 70F - ( 30,000/1273 ) = ) ~46F. That means it only modulates reasonably well from the beginning of December through the end of February, based on the temperature averages in nearby Coatesville:
https://weatherspark.com/averages/30940/Coatesville-Pennsylvania-United-States
That's not a disaster, but it's not great- you can definitely do better, and should insist on it.
With the Buderus GB142/45 you'd be looking at 45,000 BTU/hr minimum, and it stops modulating when it's above 35F, which means good modulation is only happening during the 6-7 coldest weeks of the winter once you pare the load down to 70KBTU/hr. This IS a disaster, since there's no point to a modulating boiler that can't modulate for at least half the heating season.
The Lochinvar KH-155 it can operate in modulating mode whenever its under 60F outside.
The Trinity TX151 could modulate whenever it's under 55F.
The UFT-120W could modulate nearly all the time, even if you pared the load town to 50,000 BTU/hr (if you're really ambitious in your efforts, and insulate all the walls. )
With a boiler that can modulate even at milder shoulder season temperatures it's possible to adjust the outdoor reset curve so that the burns are nearly continuous, which yields super-stable room temperatures, very high efficiency (higher than in an AFUE test if you get it right, provided you have sufficient radiation), and overall superior comfort.
Dear Mr. Holladay: Blessings upon you and yours. I think we're done with the conversation!
Mr. Taylor: Thanks for the LOL.
Mr. Dorsett: I didn't mean to put him on the defensive, but to have a dialogue. Certainly seeing your texts would be intimidating, but it could also be learning! Thanks again for your advise.
Susan ,
It is unfortunate that contractors in general do not understand what Dana is saying and instead prefer to CTA and participate in the misinformation campaign taught by the utilities and their programs . I wish more contractors and participants understood Equivalent Full Load hours and how to utilize fuel and mass a bit better . My advice is to locate another contractor that better understands these concepts
Thanks Mr. McGrath, I'm going to think about it.
Susan ,
While you're thinking about it I offer this advice . If and while you're trying to find someone else , rfind someone that does a room by room heat loss and while he is in those rooms he should also perform a radiator survey . This will determine what supply water temps will be adequate and how an outdoor reset curve is arrived at . Dana gives very good advice and your present Dan Lippin seems to have not performed the REQUIRED due dilligence to make the BEST recommendations . Try Avanti Plumbing or mechanical , Anthony Tosco should be able to help you in a much more productive way .
Man J calcs are overstated and using and leveraging what you have is oft overlooked by many . Sounds to me as if Dan just wants to install whatever he has readily available and give you heat . He has spec'd a very reliable boiler but I fear he intends on using supply water temps in what we would consider the hgh range in which case it will barely ever condense if at all , when this is done even the best boiler will not condense and thus have efficiencies not much higher than 85% and at that point you may have well gone with a well designed cast iron boiler and saved your money . Please don't allow yourself to fall victim to a Utilities"' Century Club contractor just for a few dollars worth of incentives or rebates . The rght design and installer pay off big for years while a sub standard system will surely disappoint all while you have no course of action .
Mr. Dorsett, Can I trouble you for one more piece of advice before e-mailing the contractor?
To their point that I won't be in this house forever, what if the next owners want the heat at 72 all winter, and what if the improvements don't provide the reduction in BTUs that we need. Is a 100,000BTU boiler then the right choice?
Thanks again, Susan
The Manual-J came in at 94K, and that's probably an overestimate.
If you plan to insulate the basement that will knock at least 10-15K off the total.The piping losses of 18.5K was mostly to the basement, probably an overestimate, since it presumes a water temperature that you probably won't ever need, as well as a basement temperature at least 10F lower than you would have after insulating the basement walls. If you're being conservative, assume insulating the basement only cuts the load by 10K.
That leaves a load of 84K.
The floor over the crawlspace was estimated to be 6.2K. That too is probably an overestimate, but if you insulate with fluff between the joists and continuous rigid foam attached to the bottoms of the joists it will peel at LEAST 5K off the number, but if you want to be conservative, call it 4K.
Now you're down to 80K.
The infiltration loss estimate was on the "seriouisly leaky" side at 372 cfm- that much leakage would be like 4 bathroom fans running constantly! That 22.5K of load is probably overestimating current reality by quite a bit, but if you seal up the tops of your partition walls then use a blower door to find & fix the rest of the big air leaks you'll cut that by more than half. But to be conservative assume it'll only save10K.
Now you're down to 70,000 BTU/hr.
Even if you did NOTHING for thermal upgrades on the building and installed an 80,000 BTU/hr boiler you would still be able to keep the place at 72F indoors @ 15F outdoors unless it was blowing 40 mph+ outside (the conditions under which the house might actually leak that much air.)
Code only requires that the heating system will cover an indoor temp of 68F. You are not required to meet the hypothetical needs of some future owner MIGHT want to do. Spending time & money on some future hypothetical is just silly- it's YOUR house.
Comments as I continue to try to understand the difference between smart green energy advisors who crunch numbers and experienced local contractors who are completely convinced that I need a larger boiler?
Not only did I review the boiler sizing that I was going to recommend (131000 Btu modulating) with my Bosch rep, I also reviewed with two other gentleman in this industry who have over 70 years of collective experience.
I think these people that you l are dealing with are great at making numbers say what they want them to be but I don't think in real life they make any sense whatsoever. How much wood you burn, how much oil you have used, what the temperature was in any given winter, means nothing. A house has a heating load that you need to size for which takes into consideration square footage, insulation or lack there of is all that matters. If you break your arm falling on the ice and you cannot stoke a fire you will be relying 100% on the boiler. If the house sells and the next people have a baby and don't want to have a hot wood stove running they will want to have a boiler that will heat the house-this is why the boiler needs to be sized for the house.
I would make sure they provide you a guarantee that states that you will get two years of operating the boiler and they will replace it with the appropriate size boiler at no additional charge should it not be able to keep up under the worst of conditions – because that is certain to happen.
Unless I can quote you a 131,000 BTU input fully modulating gas boiler I am respectfully declining the invitation to bid.
That said you are realistically somewhere in the $18,000 range for the boiler, the indirect fired water heater, gas piping, oil tank removal, and 10 year parts and labor warranty. It could be that my pricing is way off base from what you are looking for since so this might all be for naught.
At the end of the day I HIGHLY, HIGHLY recommend you have at least two other HVAC contractors come out to quote on the boiler and at that time you will see that I am not the one who's wrong on sizing.
Susan,
Your comments are confusing. I can't figure out which parts represent your own opinions, and which parts are quotes from misguided HVAC contractors.
What portion of your latest post represents your own views?
About 8 years ago I replaced a cast iron boiler that had 120,000 BTU/hr of output with a modulating system centered around a buffer tank (so I could micro-zone it.) At the water temperatures specified I'm limited to no more than ~45,000 BTU/hr of heat out of the radiation. The contractor who installed it insisted on indemnity on the design even after I showed him the numbers, and his hydronic designer even bet $100 that it wouldn't work (which the contractor took him up on and won.) Both fuel-use calcs and Manual-J came in between 35-40,000 BTU/hr @ +5F (the local 99% outside design temp. This place has gone through -15F temps without losing ground.
Your Manual-J came in at about 95,000 BTU/hr, but seemed suspiciously high on the air-leakage front, and unrealistically high on the piping losses (unless those pipes ran outdoors). But it also highlighted several areas where the load could be cost-effectively reduced to under 70K. If you opted to do NOTHING to improve the house it would be reasonable to install a boiler with 100K of output, but not 130K.
However, even if you installed a boiler with 130K that will be fine, as long as it's minimum fire output is under 20,000 BTU/hr (under 15K would be even better), which would give it sufficient modulation range should you decide to increase the insulation & improve the air tightness of the house later. The "...fully modulating..." in "...131,000 BTU input fully modulating gas boiler..." needs to be defined. That's fine if it has a high turn down ratio. Initially you stated they were recommending Buderus, which I took to mean the GB142 series whch only has about a 3:1 turn down. But none of that series is rated at 131,000 BTU/hr in, nor am I aware of a Buderus boiler with that specification, so what exact boiler model & number is being proposed here?
The 20,000 BTU/hr maximum min-fire output is not an unreasonable or impossible feature to demand, and I've listed several models (and there are others) that deliver over 100K at max fire that deliver less than 20K at min-fire. Again, some of those are:
HTP's UFT series have a 10:1 turn down ratio. The UFT-120W delivers more than 105,000 BTU/hr at high fire at non-condensing temperatures, yet can modulate down to about 11,500 BTU/hr in condensing mode. Both the UFT-140W and UFT-175W modulate to under 20,000 BTU/hr, if you really wanted more than 125K of output. http://www.htproducts.com/literature/UFT-brochure.pdf
NTI's Trinity TX151 delivers over 130,000 BTU/hr at high fire at non-condensing temperatures, and can modulate down to about 18,000 BTU/hr out in condensing mode.
NTI's TFT154 has a 10:1 turn down, and delivers over 130K at high fire, less than 15K at min-fire, condensing.
Lochinvar's KH-155 puts out over 140,000 BTU/hr at high fire, yet can modulate down to under 15,000 BTU/hr in condensing mode.
BTW: $18K is some to the high side for a simple boiler swap but not outlandishly high, depending on just how much work would be involved. $12-15K would be more typical in my area, and I've seen quotes for very easy installations come in around $10K (even a bit under.) Since you don't have pre-existing gas plumbing, that would be at least part of the upcharge.
Minimum fire with no buffer tank is much less likely to be a problem with bypasses such that zones are thermostatically controlled for high flow/low flow instead of on/off.
Mr. Holladay: You are right - that was confusing. Wrote it too late after a long day of work!
Mr. Dorsett: Thank you AGAIN! Here's what I got from my contractor. Now I'm faced with the question of whether to ask him to use other boilers...
Hi Susan-the boiler will modulate at any temperature and can range from 30000 Btu to 131000 Btu depending on the heat load at that time. This is a fully modulating boiler
http://mechanical-hub.com/sites/hydronics/bosch-greenstar-gas-condensing-boiler/
Mr. Jon R. Thank you for weighing in. I'm afraid I don't know what a buffer tank is, but realize from context that it has to do with micro-zoning. The contractor wants to use a Honeywell device that allow homeowners to use a remote to set the temperature from wherever they are, even though the house has only one thermostat.
Thanks again! Susan
Hi Advisors:
I got my answer back already! To whit: We unfortunately will not work with other manufacturers. We know this product and this is what we will install.
Maybe I SHOULD draw MY line in the sand at 20,000 BTUs. They did the central air in the house (before I bought it), so I'm already familiar with the company, and they're highly rated by PECO and by local rating organizations.
On the other hand, this has been a rather difficult process with them... What do you think of the Bosch? THANKS! Susan
With the Bosch Greenstar series, even the GreenStar 100 FS only drops down to ~23K out at min-fire (same as the wall hung versions), and the Greenstar 79 isn't much better. You'd have to drop to the Greenstar 57 (which isn't enough boiler AT ALL) to get under 20,000 BTU/hr.
http://www.bosch-climate.us/files/75H995076_Greenstar_Floor_Boiler_Cut_Sheet_US.pdf
If you fix the house to get it under 70,000 BTU/hr the 131 would only modulate during the middle of winter. With your high mass radiation it wouldn't short-cycle into lower efficiency or high maintenance, but it's not an ideal fit.
There is no longer much reason to go with a high pumping head heat exchanger type modulating condensing boiler with a 3:1 or 5:1 turn down ratio, given that there are now MANY fire-tube heat exchanger types with much bigger turn-down ratios, starting at 7:1, with many at 10:1 or higher. I've named several suitable models from Lochinvar, HTP, NTI already, and there are others. A pro worth their salt would be familiar and comfortable with at least ONE of those manufacturers, or another that has similar turn-down characteristics.
Bottom line is still 20,000 BTU/hr max at min-fire (and under 15,000 BTU/hr is even better.)
O.K., Thank you Mr. Dorsett,
Now I have my oil supplier coming in to give me an estimate. They say that they will put in whatever kind of boiler I want. More questions!:
1. I understand that an oil company might not be the most experienced installer of a gas furnace, but when you all say "installation is important", are you mainly saying that getting the right boiler is important, or is the actual installation tricky?
2. What would be your top choice on a gas boiler? HTP - 120W?
3. What do you think of the idea of a Honeywell thermostat that I could carry upstairs, in order to control the temperature away from the downstairs thermostat (currently the only one, around the corner from the wood stove...)
Thanks again! Susan
There's more to installing a boiler than hooking up the plumbing. The optimal pumping rates for both the boiler and radiation have to be estimated (and if different resolved in an appropriate manner with the near-boiler plumbing or system plumbing), and there are 1001 details to get right for the installation to be fully optimal.
Top choice for a gas boiler would be the one with the best local support, and would be fully backed up by the installer & distributor. You don't want to insist on a particular boiler only to find that it's the very first one in the series ever installed by the contractor.
Among HTP's UFT, series, given your calculated (and probably overestimated ) ~94,000 BTU/hr heat load along with your plans to continue air sealing and insulating projects, the UFT-100W would be the better choice than the 120W. While it would have slimmer margin at the "before" picture of the house, it probably has more than the Manual-J would indicate. It would have significant margin after fixing a few of the known heat leaks in the house.
Wi-Fi thermostats are hackable- some more easily than others, but in some markets would allow you to get paid for letting the utility bump your thermostat a degree or two during peak load events. Radio frequency linked remote thermostats are hackable too, but not as problematic as internet accessed thermostats. With either option, read up on security details.
If you want local temperature control, for additional money thermostatic radiator valves and bypass plumbing can be installed, which allows you to control room temperatures individually over a reasonable range. But that's a lot more money than an RF or portable Wi-Fi thermostat.
Thanks again Mr. Dorsett,
I took Mr. McGrath's advice and called Avanti Plumbing. When I asked Anthony whether he could install a gas boiler that modulates below 20,000 BTUs/hr., he said "Absolutely," and mentioned Lochinvar.
So I'm giving up on my idea of using the oil company (which would save me the $399 cancelation fee! Yeah, I know, penny wise, pound foolish!) and am feeling like i"m finally on my way.
Now if Mr. McGrath knows anyone who could work on insulation, that would be even luckier!
I am very, very grateful and will spread the message about GreenBuildingAdvisor.com far and wide.
Susan
I have to replace our central heating system within the next year or so. We live in a gas heated wood framed 3 story colonial with 4 zones built in 1987 in eastern MA located on the water. We have no central AC but want to install. Tankless hot water is appealing though our water tank is new. Please advise if possible. I am investigating Navien, Burnham, Lochinvar, Viessman
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Ann- rather than pile onto a thread 90+ posts in length (that may have a few more to go), please start a new thread to sort out your particulars.
It all begins with a careful heat load calculation using aggressive (=assumptions that lower the load number) where ever that is reasonable. Since you will have a heating history on the place with the old system you can use the old system as a measuring instrument to establish a firm upper bound on the sizing. Getting the sizing right, not too small, but also not too large, is key to getting the most comfort and highest efficiency out of it. The methods for using the old heating system as a measuring instrument are outlined in some detail here:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/out-old-new
If you have last winter's gas bills handy I can walk you through it on this forum, but on a new thread, OK?
BTW: If you're heating with a boiler, from both a net efficiency and hot water capacity point of view it's almost always better to heat your domestic hot water with an indirect-fired tank operated as the "priority zone" off the boiler.
Ann and Dana,
I have moved Ann's question where it belongs -- I have created a new thread for it. Here is the link: I need advice about a new central heating system.