Air Handler in Unconditioned Attic
I recently bought a house in MA (5A) with an open loop geothermal system (forced air heat and cooling). This uses two Tranquility 27 heat pumps, one for a first floor zone and one for a second floor zone. The first floor air handler is in the basement and the second floor air handler is in the unconditioned, vented attic. I know this is not ideal. I understand from the previous owner that the system struggles to provide adequate heating and cooling in extreme temperatures. I know that heat in the winter on the second floor in particular is a struggle.
I am trying to think holistically about options here. As I see them:
-Closed cell foam on the attic roof and walls: As I understand this would significantly reduce the load on the HVAC system, but it is expensive and I worry about what happens if the roof develops a leak. We are replacing the roof now so it will be new but I don’t know what happens in 20 years
-Insulate attic floor: I’m not sure how possible this and it would leave the attic air handler and ductwork in an unconditioned space. The house also has a 60s style low voltage electric switching system so there are relays throughout the attic which seems to complicate this idea
-Move the air handler and ductwork: I don’t know if this is a practical option but if the alternative is option 1 which could cost over $10K maybe this is in the realm of possibility
-Forget insulation and try to improve the capacity of the heating (electric backup) and cooling system (not sure how to do the latter)
-Other??
Any thoughts would be appreciated here as I am totally out of my depth.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
The only serious way is to put the air handler inside conditioned space, and insulate above the ceiling. I see three possibilities:
1. Insulate the floor of the attic, move the air handler.
2. Insulate the roof, make the attic unvented, leave the air handler where it is.
3. Build a "doghouse" or similar structure over the air handler and insulate that layer, have the area above it be vented.
If the attic is uninsulated it's a good indication that the person who built the house didn't know what they were doing. In addition to insulation the house probably needs air sealing and vapor barriers. Air sealing is not that expensive and in your climate could lead to a dramatic increase in comfort and economy.
Thanks. I am leaning towards #2 but I will explore #1 as well. #3 would help with the air handler but wouldn't resolve what I assume is large heat/cooling loss through the attic floor (it is insulated but poorly).
I will look into air sealing more generally. The house was built in 1964. In doing some renovation work I do see pink insulation in the walls which I was somewhat surprised by.
If you go the route of insulating the attic to bring the air handler into the conditioned envelope, be sure to read this article by Martin Holladay: Creating a Conditioned Attic.