IAQ in a Pretty Bad House, Zone 5a Connecticut
My recent blower door test has confirmed my suspicions – my 1953, single story, 1400 sq ft ranch house is drafty – 15.7 ACH 50. My HERS rater will recommend a few fixes for this, but as our original oil furnace has finally given up the ghost, I would like to know your opinions on a replacement system that addresses the IAQ.
My preference for a replacement is an LP boiler and radiators (we already use LP for many other items on the property, including the generator). With the existing ducts needing replacement, I would like to add either an HRV or HEPA unit that will utilize new ductwork (as Martin suggests that an HRV should have it’s own ductwork). The AtmosAir bi polar ionization system has also been recommended along with a HEPA system.
Does anyone have any advice about this equipment and/or plan? The heating contractors we have had look at the system just provide us with quotes for whatever we ask about and don’t provide advice (that we desperately need). By the way, we are keeping warm with a wood-burning fireplace insert that we installed a few years ago, along with a few micathermic heaters in the bedrooms, so we are prepared to take some time to get this right. Thanks!
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Propane is 'wicked' expensive per BTU
Good heat pumps would almost assuredly be cheaper to run
Keith, I did consider a heat pump along with an LP boiler backup (hybrid heat system), but the IAQ part of the puzzle is super important. Plus, anything is more expensive than the efficient fireplace insert we utilize most of the winter, even in the years we had a working oil furnace.
Now that we have lived without heat for over a month, we realize that heating individual rooms (via radiators) is ideal.
Jennifer, good for you. The best way to reduce your energy consumption is to use less. Let the sun and daylight shine in, you may find it is all you need. Keeping your home cooler reduces heat loss and putting on an extra shirt or blanket or turning off the tv and doing something is more cost effective. It's also more healthier and you don't feel the drastic change in temperature when you walk outside and the house still feels warm when you come inside.
If you get used to a cooler home, then you can install a smaller, more efficient heating system or use individual LP wall heaters.
Are you planning on tightening the house? If so, I suggest looking at the mini-splits only as your backup heat. The mini-splits have the advantage of some cooling (which we don't have yet) for the hottest days and dehumidifying during the shoulder months.
I'm heading in nearly an opposite direction - I'm looking to replace my older LP boiler (and radiators) to mini-splits as our backup and supplemental heat next year after we get our leaky house tightened up. Right now we are using only our pellet stove and I understand the desire to heat the individual rooms as they can get chilly with doors closed. Tentative plans right now are ducted for the bedrooms and have to figure out the rest.
Hi Jennifer.
What specific questions do you have?
Hi Brian,
I want to make sure that my plan to use a ducted HRV or HEPA and Bi Polar Ionization along with radiant heat is appropriate. I can't find anyone who has done this or has any advice. I know Martin advises separate ducting for the HRV, but that is usually in conjunction with forced air heat.
My questions, specifically: Will my plan work? Has anyone done this? Can anyone add anything that could help?
Thanks
Or, can anyone direct me to a place or person who could help me answer these questions?
The house leaks like a sieve. Provided the air outside is fine (ie not near highways or farm), adding in fancy filtration and HRV will do nothing for IAQ.
Basically the amount of air leaking through your house is probably 10x the amount a correctly size HRV would flow. Even if you filter the heck out of the HRV air, it will quickly be diluted by the air leaks from outside.
Switching to radiant heat will also not do much for IAQ. Typical older furnace with leaky ducting in the attic is actually pretty good for improving IAQ. They tend to de-pressurize the house and suck in even more "fresh" outside air.
Properly sized and installed radiant tends to be more comfortable in older leaky homes but that is a lot of $$ to spend for not much benefit.
Excellent points, Akos. Thank you!
>"Does anyone have any advice about this equipment and/or plan? "
For starters, get a handle on the where-is-as-is heat load of the house base on oil use in the previous system. Most HVAC contractors are going to propose WAY too much system for comfort or efficiency. A primer on how to calculate heating loads from fuel use lives here:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/out-old-new
>"My preference for a replacement is an LP boiler and radiators (we already use LP for many other items on the property, including the generator). With the existing ducts needing replacement, I would like to add either an HRV or HEPA unit that will utilize new ductwork (as Martin suggests that an HRV should have it’s own ductwork). "
Even at CT electricity rates a RIGHT SIZED air source heat pump will be less expensive to operate than an LP boiler (and a lot cheaper to install than a bunch of new radiation, be it flat panels or radiant floor.)
Unless the existing ductwork is outside of conditioned space (above the insulation in attic?) it may not need to be replaced. There may need to be some adjustments for better balance, etc. but the odds are good that the older furnace is more than 3x oversized even for the previous load, and even more oversized for the house in a tightened-up and better insulated version of the house.
The smallest oil burners found in hot air furnaces are in the 75,000-100,000 BTU/hr range, and it's not uncommon to find 150KBTU/hr burners on hot air furnaces in 1400' houses, where the 99% heat load might only be 25,000 BTU/hr, or even 20,000 BTU/hr. That means that even on "design day" the duty cycle at your house isn't likely to be more than 30-35%, with the furnace off more than twice as the amount of time that it's actually running- that is not a recipe for comfort.
A right sized heat pump will be far more comfortable than the oil-burner. The overall duty cycles will be much longer, and grow longer as outdoor temperatures drop. With the oil burner you were likely getting the hot-flash followed by the extended chill between cycles, whereas a properly sized heat pump will be yielding a nearly continuous summer-breeze flow at lower cfm with warm but not as hot as the fossil-burner's output at the registers. It's the high duty cycle that keeps it comfortable.
A big oversized pleated air filter (eg Aprilaire 2400) on the return side of a ducted heat pump system can be had in MERV 13 or higher media without imparting a large static pressure at the lower cfm of a right-sized heat pump. (I have one of those on a low-temp hydroair zone on my home system.)
Take the time to read through and watch Nate Adams' freebie chapters on comfort and HVAC efficiency on his "house whisperer" blog:
http://www.natethehousewhisperer.com/
http://www.natethehousewhisperer.com/home-comfort-101.html
http://www.natethehousewhisperer.com/hvac-101.html
http://www.natethehousewhisperer.com/hvac-102.html
Duane, yes, we are planning to tighten up the house. Over the last few years we have replaced siding and doors and the roof; we have excavated to solve a mold problem in the crawlspace and added insulation to the outside. Imagine what the ACH 50 must have been before? And we plan to replace windows and attic insulation, along with insulation in the rim joists. We had a HERS rater come out and his recommendations should come shortly. Thank goodness for GBA as I navigated all of this! Because of the layout of the house (and other issues), mini-splits won't work.
Dana, I was hoping you would chime in. The GBA article you linked to I have read numerous times, along with others on this site. It is what led me to get a HERS rater out to the house to do an energy audit and a Manual J. Re: the air source heat pump, this is exactly what I specified to two heating contractors and they both said that it wouldn't work for me without a backup heat source for the coldest days (hence, the boiler and rads). I think it will, especially with electric strip backup and our very efficient (and warm!) wood-burning insert, after all of the articles and Q&A's I have read on this site that state exactly that, along with the fact that we are living comfortably with little heat right now.
Can anyone help me find someone in my area who will not just quote me a system but be a proactive partner? If only Nate were in CT!
Thank you!
>"Re: the air source heat pump, this is exactly what I specified to two heating contractors and they both said that it wouldn't work for me without a backup heat source for the coldest days (hence, the boiler and rads). I think it will, especially with electric strip backup and our very efficient (and warm!) wood-burning insert, after all of the articles and Q&A's I have read on this site that state exactly that, along with the fact that we are living comfortably with little heat right now."
You apparently really DO know more about this stuff than the heating contractors you've been talking to.
Nate Adams' projects in Cleveland (comparable to or slightly colder than most of CT) typically end up with a 2 or 3 ton Carrier Infinity w/ Greenspeed, and some strip-heat toaster to manage the Polar Vortex event coolth.
>"Can anyone help me find someone in my area who will not just quote me a system but be a proactive partner?"
Got a ZIP code?
If you have your own heat load numbers competent installers are often found on the vendors' "contractor finder" web pages.
https://contractors.fujitsugeneral.com/
https://www.mitsubishicomfort.com/get-started/contractors
I've usually had to spec the equipment myself and push back on contractors when they say it's not enough or won't work- they're all too nervous about undersizing (human nature), when it's in your interest to be more concerned about oversizing.
'You apparently really DO know more about this stuff than the heating contractors you've been talking to.'
A better compliment I may never have! Thank you, Dana. I have been doing my very best to study the great information here on GBA (and on Alison's blog, and now Nate's) in order to get the system I really need (and not just one that will "pay for my boat so I can quit this job" - yes, one of my heating contractors actually said that. Twice!)
'Nate Adams' projects in Cleveland (comparable to or slightly colder than most of CT) typically end up with a 2 or 3 ton Carrier Infinity w/ Greenspeed, and some strip-heat toaster to manage the Polar Vortex event coolth.'
This was the exact heat pump I specified! You have given me the confidence to take all of the information provided by my HERS rater, including especially the Manual J, and move forward according to what is in my best interest.
Thank you all so very much!
If you do end up getting the Carrier w/Greenspeed, be sure to program it to NOT apply strip-heat for reheating during defrost cycles or it will chew up some of it's inherent efficiency. (That system has more bells and whistles to set up than most.)
The turn-down ratio is only about a 2.5:1, so oversizing it by very much quickly starts to reduce both efficiency and comfort. Carrier has a reasonable online tool to help size it correctly (for heating). The 2-tonner still puts out quite bit of heat even at 0F.
Click on the "Heating Capacities" tab (upper right) and select between the 2 ton or 3 ton Greenspeed on the lower left pull-down menus, and compare a number of air handler options. Even the 2-tonner
(25VNA024A**30 )has ~22-25K of capacity at +10F, roughly 20,000 BTU/hr @ +5F, even more with some of the air handler options:
https://www.tools.carrier.com/greenspeed/
https://neep-ashp-prod.herokuapp.com/#!/product/29393
https://neep-ashp-prod.herokuapp.com/#!/product/29397
A 2x4 framed tightened-up 1400' rancher can usually hit the 20,000 BTU/hr @ +5F range if it isn't being over-ventilated (or if heat recovery ventilation is used.) Since you're doing most of the heating with a wood burner don't be afraid to go with the 2-tonner + strip heat, as long as the 2-tonner covers the load in heat-pump-only mode at your average January temperature. Even when the heat pump isn't enough on it's own and the strip heat is engaged, the heat pump is still supplying most of the heat at a COP>1.
To figure out your mean January temperature, eyeballing the Weathspark graphic for your location is usually close enough. eg: Norwalk's mean January temp seems to be about 32F - 33F:
https://weatherspark.com/m/24725/1/Average-Weather-in-January-in-Norwalk-Connecticut-United-States#Sections-Temperature
In my opinion do not buy a new furnace until you have made major improves to your house.
Your house is in desperate need of work! Any furnace that began to keep your house warm in its current state will be 10 times larger than you will need after the work is complete.
Your first propriety is to seal the holes in your walls. Do not even think about insulating until you have a blower door test under 5 ACH. In my opinion if you can’t get a blower door test under 1.5 ACH an HRV is unnecessary.
I my mind the choice of LP vs. heat pump comes down to the number of BTUs you get per dollar. Without knowing your local electric rates and propane costs, we can only guess generally electric is less costly.
If you do get new duct work please make sure it gets installed inside the conditioned space and not in the attic.
Walta
The duct work is in the basement and crawl space, not the attic. It needs to be replaced because, not only is it 70 years old and leaky (I could live with that), but during that 70 years there have been mold outbreaks, animals and rust (I do not want to know what else, thank you very much) that regular cleaning has done nothing for. And I agree, Walta - I need to get the house tighter before I select and install a new HVAC. Thank you.
"A right sized heat pump will be far more comfortable than the oil-burner. The overall duty cycles will be much longer, and grow longer as outdoor temperatures drop. With the oil burner you were likely getting the hot-flash followed by the extended chill between cycles, whereas a properly sized heat pump will be yielding a nearly continuous summer-breeze flow at lower cfm with warm but not as hot as the fossil-burner's output at the registers. It's the high duty cycle that keeps it comfortable."
Here is a great example of that. I switched from my mini splits to oil heat around 8am. Notice the mini split held the house at exactly 67 overnight and the large temp swings of my ridiculously oversized oil burner. Its amazing how precise the mini splits can regulate temperature.
I am also in CT and have found my mini splits are way cheaper to run over oil. Propane in CT is more expensive than oil and hass far less btus.
Where in CT, BFW577? Can you recommend someone, or did you do the work yourself? Thank you.
I am near the shoreline in Branford. Its funny how similar our homes are. My house is a 1958 1600 sqft split level and I also have a wood insert.
Did you get the energy audit through Eversource? I did and they did an extensive amount of free work. There were a ton of generous rebates available if I had them do additional work. Ill look at the paperwork later and see the company.
I am doing everything myself as I generally dont trust other people to do it right. I air sealed everywhere, blew in cellulose over the existing fiberglass insulation, insulated the entire basement including the foundation etc.
The amount of incentives available is really generous. I so far got a practically free heat pump water heater, wifi tstat, $2 sqft insulation rebate, and a 4k incentive on my solar panels.
I did this 5-6 years ago when the incentives were amazing. I remember hearing the fund was loaded with money then and might not be as good now.
Go to the state Energy efficiency fund at http://www.energizect.com for more details.
I hired an independent HERS rater, as the company that came out to do my energy audit actually refused to do it after I told them I didn't want them doing any of the work (not even replacing perfectly good light bulbs before their time) until they told me what they recommended. They said that they don't make money unless they actually do the work. Understandable. But I also felt that an independent HERS rater would be able to give me a more broad assessment of the situation. He is also doing a Manual J, which is much-needed!
Thank you for reminding me about the fund. I do need to take a look and get any refunds that I can!
+1 for Dana’s recommendation for the large pleated aprilaire filters. They now offer up to MERV 16 filters, and also MERV 13 filters both with and without activated carbon. These filters last longer than the regular 1” pleated filters you often see, and they do a good job with relatively little back pressure. I use these filters myself in part because my wife has respiratory issues.
A “regular” heat pump with a central system will still allow the use of air filters to help with indoor air quality. Heat pumps will be very economical to run compared to propane.
Bill
Thank you, Bill. It is great to hear that these filters work for you. I will take a look at Aprilaire this morning.
Dana, thank you for the additional information! I am working on getting quotes for the Carrier Greenspeed, and the Fujitsu and Mitsubishi ducted units. I will let you know!
One more question: I have my Manual J in hand and am ready to go...after I decide between the Carrier Infinity with Greenspeed or Bryant Evolution (both 2 ton heat pumps). Any advice?
The Bryant Evolution Extreme is essentially the same unit under the sheet metal as the Carrier Infinity w/Greenspeed. As with the Carrier Infinity/Greenspeeds, the air handler selection makes a difference in capacity, HSPF & SEER efficiency, etc.:
https://neep-ashp-prod.herokuapp.com/#!/product/29237
https://neep-ashp-prod.herokuapp.com/#!/product/29238
https://neep-ashp-prod.herokuapp.com/#!/product/29243
If you go to this page: https://neep-ashp-prod.herokuapp.com/#!/product_list/
Select "Bryant" under the "Brands" pull-down, and "Single zone ducted, centrally ducted" under the "Ducting Configuration" pull down, then move the right slider on the "Heating capacity, max BTU./hr @ 5F" down to 23,000 BTU/hr, then in a separate window doing the same thing selecting "Carrier" you will see VERY similar air handler model numbers, and many identical efficiency and capacity numbers with those pairings.
If the proposals have part numbers for the air handler and compressor units, start typing the model number into the "AHRI Model, or Ur" window. The pairings will likely show up, and allow you to compare apples to apples.
The rest of the decision would be about local installer & warranty support, etc, which may vary (or not, given that they're pretty much identical.)