can someone give me the required r value for attic
insulation in michigan? I can get R-38 from the big
box store, but i seem to recall that they want R-49 ????

thanks for any advice you can give.

 

Here is a link to the Oak Ridge calculator by zip code. Your attic would go R-49 with new construction and a gas furnace.

http://www.ornl.gov/sci/roofs+walls/...on/ins_16.html

Hope this helps.

 

since it's an existing house i can go r-38 i guess. How would
you recommend I get it higher? guess with an extra layer of
unfaced insulation.

Thanks for the advice!

 

One thing that gets into the equation for ORNL to dictate the amount of insulation installed is the cost versus the payback period. I suspect that the R-38 for existing houses takes into account labor and the rate of return for that. R-49 would probably take sufficiently more labor to keep it from be cost-effective in an existing house.

If you do this yourself, the labor is more of a personal concern. The material costs for my house to go to R-49 instead of R-38 is slightly less than twice. So I would look only at the material's costs. The time to blow twice as much insulation would not be too much. After all, once you are up there with the blower hose in hand. For me, the added $300 for added cellulose in the attic would not keep me from going to R-49 instead of R-38.

How? I think that blowing cellulose is the way to go. The material is cheaper than fiberglass and works at least as well. Plus you can blow cellulose yourself. You may have a problem getting the material and equipment to blow fiberglass.

Hope this helps.