Insulation, what would you do?

[astidham]

I got an estimate today for insulation in my walls.
I was told that they could put a "flash coat" which is 1/2 inch of foam on the wall plus an r-19 batt, or 4" of open cell foam for the same cost.
how I understand it, the flash and batt has a higher R value.
what would be better in your opinion?

Thanks,

Todd

[Alan Gage]

What would I do? A lot of research.

http://www.buildingscience.com/documents/enclosures-that-work/high-r-value-wall-assemblies/high-r-wall-09-flash-and-fill-hybrid-wall-construction/?searchterm=high%20r%20wall

That's the excerpt on flash and fill. Here's the whole case study that covers pretty much every type of wall insulation:

http://www.buildingscience.com/documents/reports/rr-0903-building-america-special-research-project-high-r-walls/view?topic=resources/high-r-value

How thick are the walls? I'd be more inclined to do damp blown cellulose than anything with fiberglass batts. Would do a better job filling in all the nooks and crannies and is more resistant to air flow. It's also more environmentally friendly and doesn't cost that much (at least when I got my estimate).

Alan

[MountainDon]

The R19 batts I am familiar when fitted into a 5 1/2 inch 2x6 cavity are end up being compressed and the R value reduced to r18. If these are the same batts that would be used in your walls with the 1/2" flash foam then the R value of the batt would be reduced even further.



The foam would be great to help seal the exterior wall and virtually eliminate air infiltration. Another thing sprayed in foam is good for is to prevent that exterior skin from getting cold enough to prevent condensation of the cold surface. Not sure if 1/2" is sufficient to do that duty. Note that the buildingscience info uses 2" of foam, plus 3 1/2 batts.

Myself I like wet blown cellulose as a cost effective method of air sealing and insulating.