More Q&A Spotlight
The multistory brick home in Frederick, Maryland, is an “amazing property that deserves to be lived in and preserved,” says a Green Building Advisor reader who calls himself Joe Schmo. Its Achilles heel is a heating and cooling system that costs thousands of dollars a year to operate.
The system consists of an oil-fired boiler that supplies radiators with steam, two air-source heat pumps that provide air conditioning, and back-up electric resistance heat. There’s a 4-ton unit in the basement for the first floor, and a 3-ton unit in an attic that serves the second floor.
The 4,200-square-foot house is “surprisingly tight (relative of course), considering its age,” Schmo writes in a Q&A post at Green Building Advisor, “but my objective is to use the steam radiator/oil system only as a back up due to the large costs and safety concerns associated with using it.”
Adding insulation in the exterior walls doesn’t look like an option, although Schmo may add insulation in the attic. But more efficient heating and cooling equipment is definitely on his list. Schmo plans to replace the older air-source heat pumps with new 5-ton models.
“In this day and age, I think a well-distributed, high-efficiency system — e.g. dual unit, dual zone heat pumps — should be able to save us money over the oil-fired boiler and electric back up, no?” Schmo writes.
His question is the topic for this Q&A Spotlight.
Get natural gas if you can
Kevin Dickson recommends that Schmo look into a conversion from oil to natural gas, especially if there’s no way of adding insulation in the walls. “Gas looks to be cheaper than conventional heat pump heat for now and many years to come,” Dickson writes.
He suggests that Schmo take…
Weekly Newsletter
Get building science and energy efficiency advice, plus special offers, in your inbox.
This article is only available to GBA Prime Members
Sign up for a free trial and get instant access to this article as well as GBA’s complete library of premium articles and construction details.
Start Free TrialAlready a member? Log in
23 Comments
Wall Question
What is the construction detail of the existing walls? The owner says that adding insulation to the walls does not look like an option. Is there any insulation there now?
Probably no wall insulation (answer for Ron Keagle)
Most brick buildings in the US of that vintage are built with multi-wythe brick (no cavity), and some sort of plaster/lath with either minimal or zero cavity between the finish layer and the brick, or (as seems apparent in the basement picture) a plaster or cementicious parge layer applied directly to the masonry. Floor joists or beams are general inset into the interior 1-2 wythes.
The roof overhangs are of decent depth for minimizing exterior wetting of the masonry which bodes well for safely insulating where/when the inteior finish is going to be re-done. In the basement it's almost a no-brainer, though some amount of mortar repair or even a sacrificial parge over the entire interiror surface might be in order prior to insulating. (An inch or two of closed cell foam w/intumescent coating would likely be the cheapest. The basement floor clearly needs moisture control (both drainage + vapor barrier), even if floor insulation might be lower priority.)
The cause of the discoloration of the exterior brick above & below the first story windows needs to be figured out befere doing too much to the first floor walls. The brick gets more rain-wetting at that level than in the upper story & attic where the discoloration is absent, and the heat leak at the window drying the brick above the basement and first floor windows may be part of it, but there may be flashing issues to attend to prior to any wall insulation. Low-E storm windows would be a safe retrofit though, and may would slightly reduce the amount of rain moisture getting into the masonry below the windows.
From the coloring of the brick on the left side of the picture it's likely that there was a large porch roof which has since been removed. Replacing that with some sort of historically appropriate roof or awning at some point would help the moisture condition there. (If there were photographs or drawings available as a guide one could even preserve the original architect's vision, if one were so inclined.)
I whole heartedly agree with Peter Yost's assessment that basement to attic chases & flues are a priority before adding more attic insulation. With steam systems it can be difficult (or even impossible) to adequately air-seal the steam plumbing chase that extend multiple stories, but that's not to say you can't slow it down. The other plumbing & electrical chase are easier.
I should chime in.
First, to clarify, the existing HVAC system consists of a 4-ton electric air conditioning system serving the second floor (air handler located in attic) and a 3-ton electric AC system serving the first floor (air handler located in the basement), both with a electric resistance back up heat source. There is also an existing oil-fired boiler serving a distributed steam radiator system. I should note that the way these systems are currently wired, we cannot run the steam and electric back up heat system simultaneously (just the way it is wired at the thermostat). We are hoping to drastically reduce or abandon our use of fuel oil (due to price, inefficiency, and products of combustion) by replacing the existing electric AC systems with heat pumps, which can then provide heat and AC. We have quotes for two 3 to 5-ton units in the $15k range installed. Also, the existing electric HVAC system was installed ~1999 and appears to be well designed and installed, it just doesn't do a good job of heating the house.
You are correct in the wall details, i.e., two layers of brick with no cavity and lathe and plaster on the interior side. In the basement, there is, indeed, a layer of parging that is loose or falling on much of the basement walls, which are primarily stone and brick in certain areas. The basement floor is a mixture of bricks (oddly), "old" concrete, i.e., dirt mixed with concrete, and one area actually does have a poured concrete floor. In all cases though, no vapor or moisture barrier that I am aware of.
The brick on the exterior is in decent shape given its age and construction. Its "old" brick so suffice it to say that you cannot put a pressure washer to it. And as you can see, many spots have been re-mortared. You'll notice the overhangs on the south side of the home. The ceiling of the second story porch is slats that are open to the attic with only an uninsulated plank knee wall in the attic so I suppose you could say the attic is well ventilated. There are 4 chimneys in this old house but no real piping or plumbing chases. Most of the pipes are actually exposed in the interior spaces. We will be capping at least two of the chimneys and leaving one usable for occasional fires and installing an insert in another.
We are definitely considering some type of attic insulation and low-E storm windows in the future but the HVAC is the more immediate challenge. Our net electric rate is 9 cents/kwh and we seem to be using somewhere between 4-6000 kwh/mo. We did however blow through over 500 gallons of oil in under two months though.
Need more details.
Are his steam pipes insulated? What pressure are the boilers set at? Is the boiler water clean?
I recently bought a fixer upper with a boiler full of dark brown water and the pressure set around 3PSI. The heating bill from the month they were showing the house was $860. Just tightening up the house and lowering the temp halved that. I've since read all about steam and lowered the pressure to 0.5-1.5 PSI (may go lower after I do some math) and cleaned the water. I will also insulate the pipes this summer. I'm hoping for sub-$200 bills this winter.
It also appears he has no storm windows. Those could make a huge difference over original windows. I installed Harvey storms and now there are no drafts at the windows and it cut down on road noise, too. I also have 2 over 2s, and my neighbors either didn't notice them at all or commented that the house was looking a lot nicer lately.
Steam system.
The steam pipes are not insulated and operate at <2psi.
Walls
Joe,
I don’t see how there can be any heating plant solution without wall insulation. When you say there is plaster and lath on the interior, is that on a stud frame that provides a 4” air space? If so, could that space be insulated?
Walls haven't always had studs and cavities.
The house was built around 1850. As such, the construction methods and architecture are consistent with the period, i.e., most walls, especially exterior walls, did not use a system of studs and therefore there are also no cavities within the walls to insulate. Some structures from this period might have had some cavities depending on various factors but this one does not. It is, in fact, two layers of pressed bricks (possibly made on site or nearby) with wood strips and lathe under plaster on the interior side.
As I noted in my original posts, the challenge at hand is in transitioning the home from 19th century methods to 21st century methods with regard to the approaches used to heat, cool, and maintain the property. If applying what many of us tend to read about about everyday, i.e., add insulation, replace the windows, new passivhaus construction, etc. was applicable, there wouldn't really be much to discuss on this home. In short, none of that applies because there is nothing standard or easy, let alone obvious to change about the home other than that it has survived as long as it has, including the civil war, because it is built so well. What CAN be applied though? In fact, we actually have a second smaller pre-1800s house on the property as well.
So forget about replacing the windows for a number of reason but installing low-E storms is definitely on the list. As far as insulation, the basement and attic might be the only cost effective opportunities to add insulation. Air sealing is perhaps obvious but might also just be low hanging fruit and the chimneys clearly need some attention as well. The most urgent need, however, is with regard to the HVAC system and specifically the heating side given just how expensive oil is and how inefficient the steam system is as well, compared to more modern options. The idea is that in order to improve or reduce our energy consumption for heating, the best option appears to be heat pumps. By installing two new heat pump systems, we will reduce our financial outlay for heating (compared to oil) as well as likely reduce our energy consumption for cooling (compared to the electric air conditioning systems) and better dehumidify the home in the process. Longer term, the conversion to heat pump HVAC might also mesh better with the addition of a solar PV system even if it doesn't quite eliminate our electric bill entirely. Did I mention there is also a swimming pool...
This is a very unique, historic, and difficult property to make energy efficient so I am trying to think outside the box as much as possible and relatively speaking. It goes without saying that the property will never compete with certain modern properties or methods as far as energy consumption goes just as certain modern properties will likely not be standing and in livable condition over 160 years after construction. The wooden structural members are hand hewn from the surrounding trees in odd sizes, the pine floor planks are each different lengths and widths, the stones for the foundation pulled from the river across the street, and its located along the first national road in the US. Its been updated mechanically a couple of times in its history (originally its only source of HVAC was the fireplaces and windows); surely, there are some new approaches that can be taken to update it again considering the technological advancements over the past couple of decades.
Heating strategy
Joe,
It certainly does sound like a well-built house with lots of character and historic significance. I can understand how this eliminates your options to insulate the walls. Currently, due to the excess heat loss, the house requires excess heat, and it produces that heat relatively inefficiently. So I see the only remedy as producing the same excess heat more efficiently, which sounds like your conclusion as well.
If you do everything possible to increase the heat production efficiency, and to reduce heat loss, except for insulating the walls, here is the focus of the problem that I expect will remain, and the solution that I would consider:
The walls are highly conductive as well as massive. On average, both in their physical mass and over the daily cycle, they will be much colder than the interior air of the living space. Even at their highest temperature each day, they will be substantially colder than the interior air. Therefore, there will always be a lot of heat loss directly to the walls, through the air by radiant heat transfer. This will fundamentally require a higher than usual interior air temperature to attain a comfort level because the air temperature has to compensate for the radiant loss.
I believe the best way to offset this imbalance is to distribute the heated air as uniformly as possible, on a continuous heat production basis. So that implies an even and continuous flow of heated air reaching every location. And also, that air will have to be at a somewhat higher temperature than the average temperature considered to be comfortable in well insulated houses. It will need to be a higher temperature in the morning when the walls are colder than the evening.
Also, because of the cold walls, this objective of uniform warm air distribution would be well served by distributing the warm air along the walls, so it could raise the wall temperature and reduce the radiant loss, as well as warm the occupants by direct convention/conduction.
Generally, I think it would be impractical and very difficult to achieve this objective of uniform distribution with a typically ducted warm air distribution system. One possibility would be to distribute warm air through wooden grilled floor outlets near the walls. This could even out the air flow up the walls throughout the space.
There is a heat loss tradeoff in this overall approach, however. Bringing the heat distribution directly to the uninsulated walls, will speed up the conductive transfer through them. Alternatively, one might reason that it would be better to direct the warm air to the occupants from the center of the room rather than waste it trying to heat the walls. But the problem with that is that it will take an excess of heated air to make the occupants comfortable with that great radiant loss to the cold walls. In other words, the walls will play a big role in the occupant comfort even if occupants never touch them.
Thanks for the input.
Thanks, Ron. Oddly enough, most of the vent registers are located along the exterior walls due to how the ducted systems were designed and installed circa 2000. If you think about it, in order to not mount the air handler units right in the middle of a space, i.e., the attic or basement, so it is still usable for storage or access, the units are mounted along exterior walls, which then tends to leave most of the duct runs along exterior walls as well where they then run up or down into the conditioned spaces.
My current thinking is that out best course of action is to do the conversion to heat pump HVAC, do some air sealing, and then look into what it would take/cost to cap the chimneys, add low-E storm windows, and add some form of insulation to the attic. I am still unclear on whether there is a better HVAC option, whether there is a cost efficient option for the basement space, and what the best insulation approach is for the attic, e.g., insulate the underside of the roof and knee walls or beneath the attic floor.
All Good Things...
It seems like you have a hand on it. But for my suggestion is one that was touted earlier, get a professional energy audit. It will help you go in to your updates with a bit of confidence and a roadmap for the best directions to go first.
Best of luck, and please, keep us updated on how it goes!
What constitutes a good audit?
A couple of the HVAC contractors quoting us the heat pump installs have offered to perform an energy audit for free or for $100 after the local utility subsidy of $300. What should be on the list of items on a decent energy audit, e.g., door fan blower tests, thermal imaging, etc?
Consider Using a Wood Pellet Boiler
Natural gas is not the only lower-cost fuel option when considering alternative fuels to oil. Wood pellets are a viable regional fuel source that can be used via an automated pellet boiler to deliver the BTUs you need. The virtues of pellets are many: most notably, it is a renewable non-fossil fuel resource and costs around the same price per BTU as natural gas.
Given your existing infrastructure, you could potentially convert the existing radiators to hydronic, install new radiators or baseboard, or utilize the existing ductwork via a hydronic air handler. Fully automated pellet boilers also allow for the homeowner to be almost as hands off as an oil or gas boiler aside from emptying an ash bin a few times a year. Granted, the investment is not small, but depending on your annual heating costs it may be well worth it.
I'd recommend taking a look on Hearth.com and also doing some online research to see if that route makes sense for you. Here at ReVision Heat in southern Maine, we have been ecstatically ripping out oil systems and replacing them with the Kedel pellet boiler. We also have a couple bulk pellet delivery companies that will blow them into a 3-ton hopper so the homeowner is as hands-off as possible.
how about electric radiant heaters?
Or so-called "cove heaters". The idea is to heat the people in the room via radiation rather than convection (ie, warm the air which warms the people). You can aim the heaters so they radiate towards where people congregate -- kitchen, dining tables, couches, desks. Then put them on motion sensors so they're only on when people are there. This mitigates the problem Ron mentions above, namely that the walls will always be colder than the air, so they will continually suck warmth from the air. If you focus less on heating the air and more on heating the people, you can set the thermostat much lower and still be comfortable.
Hybrid Heating and Cooling Systems
As a General Contractor that specializes in Historic Homes in Frederick Maryland and a property owner of an historic home (1858) in Frederick Maryland I have found that a strategy of considering the many options available and developing a multi systems approach to heating and cooling of older homes to be the best solution. Careful planning and research can keep the costs of upgrading heating and cooling systems within the realm of reason. Example: Our property (about 2600sf) was heated with an oil boiler and circulating hydronic baseboard. For AC this same property separate 2 ton AC unit. We replaced the (please forgive my lack of technical terminology) AC with a 13 SEER air source heat pump for heating and cooling (2.5ton) (not the most efficient available currently) and wired the existing oil boiler to act as a back up heat source. The previous winter the heating took 3 tanks of oil, this past winter only 1/2 a tank with only a minimal increase in electrical costs. As far as I'm concerned this was a success, these homes can be heated and cooled far more efficiently for a reasonable cost if you put more planning time into your system/s.
Thanks, Charles.
Could you by chance recommend someone for some projects, i.e., seal a few chimneys, mortar stone and brick exterior, add insulation in the attic, etc? We have many projects to do...
If you have the ground space
If you have the ground space outside the best solution is a Ground Source Heat Pump. I had a LP forced air system and the cost of LP was up as high as your oil. Natural gas just adds more methane to the atmosphere and resistance heating does little for air conditioning. The ductless minis aside from looking ugly on the inside really do not work well in areas with temps above 77° and below 35° that is because the units are trying to pull the temps out of the air. A GSHP pulls the temps out of the ground which at our Latitude is a constant 55° at five feet below grade. We went from a heating-cooling billing of $2,200 per year to $600 per year. The cost of LP is running $4.23/gal., electricity is running .0949/kW. The federal Gov. offers a 30% tax credit and most power companies also off a direct rebate, ours was $1,500.
I have an old house and antique furnace
Wow - I can certainly relate the the homeowner with a historic house. My house was built in 1910 and restored. I try to keep everything as authentic as possible. I have a 1942 octopus furnace that I have been using and paying a lot in oil bills. It's not that expensive for me since I keep the heat very low.
I was faced with a similar situation last year and wrote an article about my experiences. The bottom line was that I kept my antique furnace and had a new furnace also installed. Check out my article and see some cool photos and my reasons for doing what I did here http://www.oldhouseguy.com/heating-old-octopus-furnace/
Cost per kWh
Hi Joe,
What accounts for the miniscule rate per kWh? And on steam chases, why can't they be sealed with standard spray foam reserving the area of steam pipe contact for fire code foam?
Charles Poteat
How large an area of land was required for your 2.5ton GSHP?
Thank you,
Scott
We have plenty of land but also have a well and septic
James,
My understanding though is that a ground source heat pump loop would be quite a bit more expensive. Is the tonnage for a ground source system the same as ducted? If so, we would need between 7-10 tons of conditioned air.
Scott,
I'm not sure what you mean by minuscule rate. Our utilities rates are lower than some parts of the country but the ~9 cents per kWh is the net price we pay. As far as our usage, my 4-6000 kWh per month reflects the shoulder spring season where usage is lower than winter or summer. And I don't believe Charles referred to a GSHP, but rather ducted air source.
Energy Auditor thoughts
I have been a home inspector for over 10 years and an energy auditor for local utility company for 5 in the home owners area. It was stated home is "relatively" air tight. Has a blower door test been performed? What is the number. I have never came across a home built in this time period that was relatively tight. You need .35 ACH for sufficient fresh air. Most homes in this period has 5 to 10 ACH. Excessive air leakage results is the number one source of energy loss in this era homes. Some facts:
Air sealing older homes typically saves 3 to 4 times more energy than adding insulation
It cost about a third to a half the cost of adding insulation
Air seal will pay for itself in 1 to 3 years, insulation 7 to 20, windows 50 to 60.
The building envelope (air seal-insulation) should be done BEFORE upgrades to mechanical systems for correct input into manual J calculations. Else you may end up with an oversize system that will not properly dehumidify the air in the summer. Proper air seal and insulation will most likely result in smaller system.
I'm not knocking insulation (I'm a Participating contractor for air seal and insulation under the MD Home Performance with Energy Star program) but air seal and insulation go together and the air seal needs done first. If you purchase your electric from Potomac Edison your home may be eligible for 50% rebates up to $2000 for insulation of air sealing.
Once the air seal and insulation has been completed, I would then look at heating, cooling and hot water via geo-thermal. An audit from your local utility company will issue a report that provides approximate cost and energy savings for each recommended improvement.. Hope that helps.
Terry Wigfield
Home Energy Team of WMD
No audit done yet
The home is relatively tight in that most of the interior plaster has been refinished, ductwork is insulated, mortar repointed, many gaps seal or caulked etc. That being said, a door blower test has not been done yet but is planned as part of an energy audit. Unfortunately, it looks like the audit might get done after the update to the HVAC system since that is the more urgent matter and because the audit will likely not impact the results much in that updating the windows isn't in the cards nor is adding attic insulation in the short term.
Without an audit you're guessing
You love the house because it's unique. It needs more than cookie cutter solutions. Get an audit from a qualified, independent HVAC engineer. That's the only way to identify the problem and make on target solutions. An independent engineer will reduce the bias towards a particular system or what a contractor happens to have experience with. The contractor who knows mini-splits will say mini-splits, the wood pellet guy will say wood pellets, and the old house guy (thumbs pointing to myself) will tell you to put the windows on a lower priority.
Speaking of windows, get that audit (it should even be able to sort out your good windows from bad), than restore the windows that need it knowing that recent field tests conducted by the Window Preservation Standards Collaborative show that vintage wood windows can be restored, without storm windows, to meet IECC 2012 standards for air infiltration. The key component is to add a brush sealed stop to the sill where it meets the bottom rail of the sash. Storms have their advantages, but most also cause the occupants to operate the windows less. Opening and closing windows (especially lowering the upper sash so it vents at the top of the window) is a key part of "manually" operating your vintage house to set up the best convective air flow. April/May and September/October are good marginal periods where you can control your temperature mostly with your windows. With storms though, you'll likely not bother and just let your system do the work for you. It's a human nature thing.
Log in or become a member to post a comment.
Sign up Log in