Best way to insulate with a furnace in the attic
Hello, I have never posted in this forum, but I am not new to GardenWeb. I am hoping the collective wisdom in this forum can help me in a new situation.
We just purchased a home in northern Illinois. There are 2 attics and 2 furnaces. Both furnaces were replaced in 2010. The older part of the home has a larger attic with maybe R3 of old rockwool. The furnace is in the basement. The newer part of the home has a small attic with maybe R15 of rolled fiberglass. The furnace is in the attic here. Both attics have some duct work (which is encapsulated in insulation).
We know we need to insulate. I have talked to traditional (blow in fiberglass) and spray foam contractors. The roofer says the spray foam will reduce the life of the roof. I'm worried about that furnace in the attic. I sort of think we should spray foam that attic space because it seems to me that the furnace should be in an "indoor" space. Of course, spray foam is very expensive, so I am not sure I want to spring for it in the larger attic, which could be addressed with traditional insulation.
What do you all think? Should I worry about the furnace in the attic? If we insulate to R60, that attic is going to be mighty cold in the in winter and hot in the summer.
Thanks in advance.