I am planning to build a 32×40 garage, gambrel trusses with a bonus room in the second story. I also plan to have radiant floor heat in the slab and in the joists to the bonus room. I live in Mid-Michigan.
My question is what is the best way to insulate. I would like to spray foam a portion of the building (roof/ceiling) and conserve costs by going with batting on the walls. I am having 2×6 construction on the walls which will give me some extra room there.
Is spray foaming the roof deck and not venting the building the way to go? Or should I vent and insulate around the bonus room and the ceiling of the first floor? I have read that this can cause some moisture problems and that applying the spray foam to the roof deck is the way to go as it provides a moisture barrier and insulated directly from the outside temps, but will create a larger space to heat?
As always, your suggestions/experience is appreciated.
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