Insulating the garage ceiling – bedroom above
I am in a 4000 DD cold climate with humid summers
An HVAC system is installed with no HRV. A/C is run in the summer
The room gets cold during the winter. Currently there is a duct between the ceiling and the garage that is covered with drywall (i can’t tell whether it’s suppy or return). the height of the bulkhead is maybe 3 feet.
The plan so far is to remove the flimsy, decrepit garage doors with new thermally insulated ones, and to do the best to eliminate air drafts.
1. If the duct is not insulated, is it usually sufficient just to insulate the duct (and not the garage ceiling/floor)? or would insulating the floor as well make a dramatic difference in addition to insulating the ducts.
2. My usual instinct would be to “foam” the supporting joists under the bedroom floor, but after reading the large comments section in this site about people getting sick from iso and polyurethane foam due to the blowing agents off gassing. I don’t know if I will ever reccommend foam products that cure onsite (minus the cans “great stuff) The question is if I don’t foam, is it possible to flash the underside the rafters as a vapour retarder?? if so using what material?
3. If the flashing is a vapour retarder, can I use cellulose insulation in this assembly? what would hold the cellulose “up” I don’t see how it is possible to use dry densly packed cellulose. Maybe someone here could provide a proper method.
4. should i insulate the garage walls? (connected to the outside) or is this not neccessary since it is not a heated space.
5. finally, even though cellulose is environemntally friendly, is it appropriate for a non-heated garage to bedroom location.? if not, what are the best methods(s) or best options to insulate a garage celiing.
thanks for the help.
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