Spray foam insulation seals tight

You have many great choices of insulating material these days. Most builders use fiberglass batts, which is the cheapest way to meet the code requirements. But if all you want, or want to build, is a house that meets the code requirements you're probably not visiting this website. After all, code simply defines the cheapest house that can be build without going to jail.  One the other hand, I have known good builders who favor fiberglass, with the huge caveat that it be installed correctly - and that can be a "big if".

Spray foam offers some tremendous advantages over batts, or even blown cellulose. Firstly it's an air barrier, so in one swoop you seal the house tight and insulate well. Secondly, there's a lot less concern about the quality of installation because there are simply a lot fewer things that can be done wrong. Thirdly, if offers the added benefit of superior sound insulation too, so you'll enjoy a quieter home as a bonus.

Comments

[PJ]

Curtis
Shingles softening and natural cooling from vents are both non-concerns. The shingles will not get any hotter by insulating underside. They gain heat directly from solar radiation. And 95% of the heat in an attic comes from radiation too. Venting does nearly nothing to reduce attic heat and absolutely nothing to cool shingles. There's a great article on BuildingScience.com - "Joe's Top Ten List of Dumb Things To Do In The South" at http://www.buildingscience.com/bsc/topten/south.htm" - which substantiates this.
Plus by insulating the attic, should you run ducts in that area they'll perform better. I think Joe's article covers that too.

You're much better off sealing the house tight including attic and crawlspace.

Feel free to get in touch directly if you want to discuss your house design or other issues.

PJ

[Curtis Keeling]

I am designing a new house and definitely see the benefits of spray foam insulation. There is a 4th benefit that you did not mention and that is improved structural capacity due to weak axis bracing of framing members. However, I must admit that I am very concerned about spraying foam insulation directly to the underside of the roof sheathing to provide an insulated attic. Have you heard of any issues with shingle softening due to the missing air space and soffit vents which promote natural convection cooling?

Thanks!
Curtis