How Important is Insulating Floor Between (Heated) Garage and Living Space?
I’m building a structure (described in depth in this thread) that includes an insulated, heated garage on the first floor and a living space on the second floor. The entire building envelope is going to be insulated (walls will get 6″ of fiberglass in the stud cavities plus two inches of rigid foam on the outside).
In order to avoid the need for a center beam and columns, my lumberyard recommended 16″ engineered I-joists for the floor, allowing me to span all the way from one side to the other without support.
The problem with those I-joists though is that, from my conversation with an insulation contractor, they are very difficult to effectively insulate, with the only really effective options being either spray foam or blown in cellulose or fiberglass, any of which would be very expensive.
My question is, given that the garage will be insulated and heated but with a lower necessary temperature than the living space above, and given that heat rises, is it actually necessary to insulate the floor between the spaces at all?
Thank you all in advance for all your help!
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