Spray Foam Insulation Choices
Friday, March 7th, 2008 at 8:03 pm 
By Ryan BrownInsulation is a critical component to any high-efficiency home as it separates interior air temperature and humidity from the outside. In Austin, interior air conditioning is one of the main components of our electricity consumption. We can protect our investment in conditioned air by building tightly insulated homes. As for insulation options, here is a video with a nice summary from local builder Alex Pettit of Risinger Homes:
A more detailed list of insulation options can be found here: Wikipedia-Building Insulation Materials.
For my personal remodel/addition project I am leaning towards spray foam insulation for walls and for the underside of the roof decking (for my unvented attic). Spray Foam is generally more expensive than most of the other options, however it provides a good R value in addition to an air-tight seal. It is a common feature in many of the homes on the annual Austin Energy Cool Homes Tour.
Spray Foam Insulation Options
So I have decided to install spray foam insulation. Decision made, right? Wrong. There are still a few questions I have to answer:
- Will I use open cell or closed cell foam?
- Which brand of foam will I use?
- How does this decision affect other home systems?
Open Cell vs. Closed Cell
As the name suggests, the difference between open & closed cell foam lies in the internal structure. The tiny cells in open cell (oc) foam are broken, allowing air to fill the gaps. Closed cell (cc) foam consists of just that - tightly packed closed cells. This results in cc foam being heavier, more rigid, and more expensive than the oc variety. CC foam also has a higher R value per foot and better resists the leakage of air and water vapor. Here are more details Sprayfoam.com - Closed Cell vs. Open Cell Foam.
I am currently researching which variety is more appropriate for our climate. I believe oc foam is much more common around Austin, but I need to do a little more homework. The cc foam’s resistance to water vapor leakage is the critical consideration. It’s important to keep moisture from entering the home, but it is also critical to allow for moisture to escape in a safe manner (to avoid mold).
Spray Foam Insulation Products
Like any other product, there are several brands to choose from. Here are the main contenders I am considering:
- Icynene (oc)
- BioBased (501=oc, 1701=cc)
- Demilec (Sealection 500=oc, Agribalance=oc)
- NCFI (Sealite=oc, InsulStar=cc)
The Biobased and Agribalance foams have the added bonus of being based on soybean and vegetable oils.
Impact on Home Systems
By choosing this technology for insulation, I believe I have to consider the following:
- Reducing the HVAC load through air-tight, high R-value insulation
- Choosing an HVAC system built for a sealed attic
- Sealing around wall/roof penetrations (windows, pipes) to maintain airtight envelope
- Installing all the wiring I’ll ever want in the walls before insulating
Related to wiring - I have heard tales of Spray Foam insulation melting wire jackets. (See the AVS Forum thread here) I believe the reaction that causes the foam to expand is exothermic (releases heat). It will be critical to verify that the temperature rating of any wiring is high enough to withstand the temperature of this reaction.
Conclusion
The above is a result of my research thus far. I will fill in the gaps as I progress, but I welcome building professionals reading this blog to chime in with any advice based on their experience. Obviously the end goal is to choose the best material for our application & budget.
