[zwrogers7259]

Designing a new house and looking at different insulation/decking options. I had planned on doing Zip panels for decking, with 4" of spray foam on the underside, but I've decided to go with ductless mini split for heat/air so im not sure if it's necessary to condition the attic.

Now planning on going with techshield decking and 12" of blown cellulose that I'll spray myself.

Am I wrong in doing this? Location is lower part of zone 3. Just feel I might be going overkill with conditioning an attic if no ductwork is there.

 

[Nealtw]

A closed system with insulated roof sheeting is second best to a vented attic.
There are a few ways you can have duct work or AC in top of house and keep it inside the envelope of the house.

 

[SPS-1]

I can't see why you would make an attic a conditioned zone even if you have ducts up there. A lot cheaper (in energy) just to insulate the ducts. Maybe there is something I am not seeing --- putting ducts in attic is very rare up here.

 

[zwrogers7259]

I can't see why you would make an attic a conditioned zone even if you have ducts up there. A lot cheaper (in energy) just to insulate the ducts. Maybe there is something I am not seeing --- putting ducts in attic is very rare up here.

Down south there is a major push to fully encapsulate the attic usually with spray foam. Gable walls and the underside of decking are sprayed usually with open cell foam, creating a near air-tight space. This is done to keep the temperature of the attic within 10 degrees of the living space below. Attic temps here can reach 130-140 degrees in the heat of summer. Most ductwork is only wrapped with i would guess R-3 insulation and is found in the attic 90% of the time.