Insulating cheap and green for a garage roof and door
I have an unfinished garage here in Minnesota, wanting to insulate it and add a heater so it can be used in the winter. Managed to find some R15 faced insulation for the walls off craigslist.
I got a bid for spray foam for the roof and they pitched the benefits, but I’ve still got some sticker shock ($3600 for about 750 sf at 3″ thick R21). Do folks here have recommendations on the best approach for insulating the interior side of the roof (leaving rafters open) that is both affordable and green? If spray foam is the way to go I can do it, just trying my best to weigh my options.
They also pitched me on a fire retardant paint they suggest I spray over the foam, but that’s nearly $1000 extra. Is that necessary?
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