Attic heat loss problem
Hi,
About 2 years ago I purchased a DC row house circa 1912. The Previous owner installed a central a/c unit with the condenser on the roof and air handler in the attic and it serves everything but the basement. The problem is that in mid summer the a/c hardly keeps up, especially on the 2nd floor and my bills are quite high considering the ac system is only about 7 years old, and its a row house.
The attic is an unconditioned space, and the insulation at the attic floor is very old and compressed. Problem with fixing that is that it would require removal and re-installation of the attic floor, and some kind of temporary support for all of the a/c ductwork during the process. So, that seems very expensive.
I am open to all suggestions, but I need improve my energy efficiency and/or improve ac equipment in order to keep the house cooler in summer. The heat is a modernized radiant system with NG boiler. It keeps up fine, but I am sure I am wasting energy through the attic. I think I have 3 options, 1) Do the difficult work of removing the attic floor, re-insulation (probably closed foam since only 6″ space), and reinstalling floor. Keep attic unconditioned. 2) Seal and insulate the roof and bring the attic into the conditioned space. 3) Replace the entire central system with multi zone mini ducted or ductless system and perhaps some combination of 1 and 2.
I think option 3 should have happened when the a/c system was replaced about 7 years ago, but now that seems like a waste. Although it would probably yield the most energy efficient solution.
I hope that wasn’t too long winded, and I appreciate any help offered.
Andrew
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Replies
Hi Andrew.
Air sealing and insulating the attic floor will help make the house more efficient and comfortable, but you'll still have ducts running through an unconditioned space, which is not efficient. If you are going to do all of this work, why not insulate the roof and bring the attic into the conditioned envelope. Seems like you have a low-slope roof. You may find this helpful: Insulating Low-Slope Residential Roofs.
Hi Brian,
Thanks for the quick reply. So, the roof is a 7 year old single layer member with solar panels installed over, so any insulation would need to be installed from inside the attic. What do you think about just using 5 to 6 inches of closed cell spray foam into the rafters and front and back walls? I believe that should be air tight and the moisture would go back into the conditioned space. In that case do I need to add a vent from the ac or perhaps a new split unit to air condition the attic as well?
I totally agree with Brian: converting the attic to conditioned space will probably be a big help here. It’s not a fun project, but it’s likely the best option you have.
Having spent a fair bit of time in your area and seeing a number of similar row houses (mostly around Baltimore) since I have a friend who renovates them, I can tell you you should also look into air sealing the basement. A lot of the old brick work and basement “details” is in rough shape in those old row houses. There was a party wall on one place in Baltimore that collapsed during the Reno of a neighboring house which resulted in some exciting legal issues that had to be dealt with. Air sealing the basement will help to reduce stack effect.
Bill
The basement is finished now and sealed except the wall to the back of the house. We use a dehumidifier in that back utility room that keeps it very dry and have never had issues with moisture. I suppose I could replace the door out the back of the basement and spray foam the utility room wall at the same time which would completely seal off the finished basement.
In the houses where you did this in Baltimore, what did you use to insulate the rafters?