Fires From Spray Foam Rare
The article about residential fires attributed to spray polyurethane foam (JLC Report, 10/11) states that I see the risk of fire from foam applications as minor. I hope readers understand that I do not imply that a fire that causes injury or death and major property damage is minor; only that the actual occurrence of fire attributed to spray-foam applications is extremely rare. I have extensively researched fires attributed to foam applications in order to develop fire safety documents, which were published by the American Plastics Council around 10 years ago. At that time, no fires were reported in houses, but a few were reported in commercial applications (caused by cutting or welding torches). I am aware of four fires linked to spray-foam applications over the last five years. To put this into perspective, conservative estimates indicate that there have been approximately 5,000 residential insulation contractors spraying foam during the last five years. If each of those contractors sprayed 25 houses a year, the total would be 625,000 jobs over that period. Assuming four fires have been linked to spray foam applications, that would be less than 1 in 100,000.
The article also reported that I said you would have to pile on a foot of foam or more for it to spontaneously combust. I think the word I used was "typically." Depending on chemical formulation, site conditions, and spray equipment settings, spontaneous combustion could occur in thinner or thicker applications.
I appreciate that you published my technique for installing foam lifts in the proper thickness, using a simple meat thermometer. Measuring the temperature of the curing foam can eliminate or minimize a lot of potential problems.
Mason Knowles
Savannah, Ga.
Exterior Foam and Moisture Problems
Here in Maine (Zone 6), we learned a long time ago that adding foil-faced foam to the exterior of a home ("Making the Most of a Siding Replacement Job," 9/11) can have disastrous results, because the product creates an extremely good vapor barrier. The article should have discussed the potential pitfalls of not adding sufficient foam thickness to prevent condensation in the wall cavity, as well as the unintended consequences of air-sealing a home to reduce air changes. The subject house is 120 years old, and has done just fine most likely because there's no interior vapor barrier and plenty of air movement in the exterior walls to dry things out. Applying a vapor barrier on the outside and reducing air leakage must be done thoughtfully, as it can increase vapor pressure, forcing more water vapor into the cooler exterior wall cavity where condensation can occur.
Bob Theberge RC Theberge General Contracting
Brunswick, Maine
SIPs Fan
The author of the article "Building a Simple Passive House" (8/11) works too hard to create an energy-efficient house. He starts with an inherently inefficient structure - stud framing - and applies lots of labor and materials to make it perform well. It's an outdated concept. Structural insulated panels have been around for over half a century; properly installed, they solve the structural, insulation, and air-leakage problems while reducing labor and some materials.
B.A. Thorne Timber Valley Builders
Trinidad, Colo.
Restoring Old Windows for Efficiency
The clip about the National Window Preservation Summit (JLC Report, 9/11) misses a valuable goal of the session: proving the energy efficiency that results from restoring and weatherizing old windows. Several days were spent testing windows in a historic building before and after restoration; the results of third-party air-filtration testing will be presented in late December. It is not just about preserving the beauty of old windows - it is also about durability and longevity. Old wood and metal casement windows have often survived for centuries; you can't buy new windows with that kind of life expectancy. For more information go to ptnresource.org/WPSC.
Catherine Brooks Eco-Strip LLC
Reston, Va.
