Conditioning area around attic air handler
I have a 2 zone house – so the 2nd floor is heated and cooled by a heat pump with an air handler in the attic.
I don’t have any actual numbers but obviously in both seasons the air handler is operating in extreme temperatures that must impact its efficiency.
I would like to construct a room of sorts about 8x8x8 out of thermaply since it is light enough and flexible enough to fit through my 22×30 attic access in 48×96 sheets. I would then like to apply about 4 inches of spray foam to fully insulate the area.
again this is just an air handler so there is no combustion air or flue to deal with so the main questions I have are:
how to provide another access to be able to get to the rest of the attic
type of spray foam to use open vs closed cell
other insulation options other than relatively expensive spray foam
Is this worth it? I’m figuring about $100 for the T-ply and about ?$400? for the spray foam.
Thanks
Jeff
Replies
Note that you could enclose the air handler in any material and come out ahead in terms of heat gain/loss -- doesn't have to be highly insulated. Just building a room out of clear vinyl or housewrap would work. I'd think hard about maybe using "fanfold" like they use under vinyl siding when going over existing siding -- it comes already folded up, has a nominal amount of insulation, is just about the cheapest sith you can find, and should be easy to handle. (The downside is that it's perforated to prevent moisture trapping, and so will not seal up perfectly.)
Skip the spray foam -- not going to pay for itself in this duty. Maybe staple up cheap bubble wrap insulation or some such, or just double up on the fanfold or whatever you use for the walls.
As for getting to the rest of the attic, it's hard to speculate without knowing anything about the layout. You can always create a hatch in a closet, but closet hatches are not ideal. The other route would be to arrange your "room" so you can move aside a wall or what not to gain access to the rest of the attic.
Looking at the space again and considering the possibility of not insulating, just airsealing, perhaps I will built a much less spacious but probably more effective 4x8x4 space.
I'll probably build the box and get some before and after temperature differentials and then reconsider the insulation.
Thanks
Jeff
You do want to try to enclose any air ducts that are apt to be leaky. The zone dampers (if you have them) tend to leak, so it would be good to enclose those.
The trick is to balance the leakage -- you'll generally have more air leakage out of vs into the AHU and closely associated ductwork, so it may be necessary to make a small "intentional leak" in the return ductwork to achieve near balance. Otherwise the pressure will force warm air out through leaks in your "room".
Making a "window" out of plastic sheeting in the otherwise rigid room (if you do indeed go with some rigid material) will allow you to tell how much pressure there is, based on how the window bulges out (or in).
We did a duct blaster test on this zone and were at about 3.5% leakage so I'm pretty happy with that - so I think rather than making the room larger to enclose more ductwork I'll make it as small as possible to benefit the air handler as much as possible.
I think once I have the room build I will try to temporarily convert my attic access hatch to a piece of poly so I can gauge the pressurization of the air handler room. Hopefully that piece of poly would not be overly taut in either direction indicating that there is a decent pressure balance.
I think once I have the room build I will try to temporarily convert my attic access hatch to a piece of poly so I can gauge the pressurization of the air handler room.
Just make sure your new enclosure is well sealed, Otherwise your poly may not tell you the real story ... although it isn't exactly rocket science. Could be affected substantially if the day was windy or not ... which places additional air pressures on your 'system' (i.e. the house and AHU combined).