Insulation
I have read several articles about how much and which kind of insulation to use which is just confusing me. I will be building a house near Montgomery,Alabama in appox. 4 years and I know things are changing all the time. Some people say the best insulation is the sprayed which I guess is right because it covers all the holes. Would 2×4 frame house with sprayed foam be enough insulation? Do need rigid foam? I plan on having crawl space with concrete floor. On the blogs there was section by Matt Risinger, what do you think about his ideas on insulation? In his article they use a two part insulation by Dow where you spray all the joints with a latex chalk before installing insulation. If you use used sprayed insulation would it be over kill to use a chalking like that or would it be a good idea? If so any ideas?
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Replies
William,
If aren't sure how to insulate your new home, you have two choices:
1. Start studying up on the issue by reading as many articles as possible on sites like GBA and BuildingScience.com.
2. Hire an experienced builder, designer, or energy consultant to advise you.
You are located in Climate Zone 3. According to the 2009 International Residential Code, the minimum R-value for walls in your climate zone is R-13.
There are a wide number of different insulation materials that can be used to achieve R-13. You can read more in the GBA Encyclopedia:
Insulation Overview
Insulating Roofs, Walls, and Floors
Insulation Choices
One of your questions concerned sprayable caulk. To learn more about those products, read Air Sealing With Sprayable Caulk.
If you choose to install spray polyurethane foam insulation in the stud bays of your walls, you don't need sprayable caulk.
If you are going to use Spray Foam i encourage you to look into Green Guard certified spray foam in order to reduce indoor air toxins that result from the off gassing of these products. Also, i would encourage utilizing an Energy Recovery Ventilator or Heat Recovery Ventilator to bring in fresh air to your ideally air tight efficient home. Go to Greenguard.com and search for insulation. 2 of my favorite greenguard certified spray foams are Certainteed and Biobased
One of the articles that I saw said the spray sealed around the bottom wall next to the floor. Would I get leaks there if I had spray foam? A second question is my wife wants a storm shelter under the house and we want crawl space so would it be better to try for a basement? And what do you have on storm shelters?
William,
Q. "One of the articles that I saw said the spray sealed around the bottom wall next to the floor. Would I get leaks there if I had spray foam?"
A. Your question is unclear. Are you talking about gaps between studs and OSB sheathing? Or gaps between the bottom plate and the subfloor? Or some other type of crack? Please explain.
Q. "My wife wants a storm shelter under the house and we want a crawl space, so would it be better to try for a basement?"
A. If your wife wants a storm shelter under the house, then you had better build her a basement, unless your wife likes to crawl.
Q. "What do you have on storm shelters?"
A. Although GBA doesn't include construction details for storm shelters, you'll find plenty of information available on the Web. Just Google "storm shelters."
Mr. Holladay,
I was talking of cracks between the botom plate and the subfloor. The article showed them spraying that area and he led me to believe that there would be leaks around the plate.
Second what I mean to about the storm shelter and the basement is some floor plan offer half or full basements. I thought it would be better with a full one because of all the water proofing. Even if I get a crawl space, I still want a concrete floor in it with at least 40 inches ground and the floor joist.
William,
1. I don't recommend the use of spray foam to seal the crack between bottom plates and the subfloor. This crack should be sealed with a gasket (installed at the framing stage) or caulk (also ideally installed at the framing stage, although it can be installed later in a pinch).
2. You're right -- it's possible to build a house with a basement, or a crawl space, or a foundation that is half-basement and half-crawl space. Anything is possible, and the decision is driven by the site -- is it sloping or flat? -- by your budget, and by your preference. You're the homeowner, so you get to decide.
Since you wrote, "I thought it would be better with a full one [basement]," it sounds like you already know what you want.