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I have been trying to figure out what type of insulation is best for my house.  It has not been easy.

Here are a couple of the things I ran across that people were saying about foam insulation:

As for installing foam insulation in the attic, I would be very careful. It is possible to spray foam directly to the underside of a roof. This can keep the attic space very comfortable indeed. Consider doing this if the heating and cooling equipment must be placed in an attic space. If this equipment and the connected ductwork are exposed to extremes of hot and cold, it can lead to higher energy costs. But keep in mind that the attic is often the sole pathway for excess interior water vapor to leave a home. Some foam insulations may significantly block the movement of water vapor. In addition, be sure the foam is the open-cell variety so if there is a roof leak, the liquid water passes through the insulation and is not trapped against the wood roof sheathing and framing lumber.

Furthermore, applying foam insulation that close to the underside of asphalt shingles may create a secondary problem by causing the shingles to overheat. I would make sure that spraying foam insulation to the underside of the roof does not void any warranty on the roofing materials.

Yes
Air leakage <0.001 L/s/m² @ 75 Pa at 1.5” thickness

Allows Moisture Vapor In - no

R-value 3.5 per inch

Open-Cell Foam

Allows Moisture Vapor In - yes

  Yes
Air leakage 0.005 L/s/m² @ 75 Pa at 5.5” thickness

May 27th, 2008

More on insulation, I found an insulation calculator and it figured that if I changed the insulation on my house from R-22 to R-29 it would save around $100 per year in heating.

So for the $6000 investment it would take 40 or 50 years to make up what I would be spending.  So I am going to go with less insulation.

Those numbers are based on insulating the walls and ceilings so just doing the ceilings would make even less difference.  The contractor said they had a report that it would only make around $10 per year difference.