Decision Point: Foam Products

We put our minds to the subject of foam products for our building. Why? Most conventional homes rely heavily on plastic foams for insulation, like XPS, EPS, and spray foam. While highly effective insulators, they come with several concerns. They require high embodied carbon in their manufacturing and neither recycle easily nor break down easily in the waste stream. Many products are accompanied by the use of toxic flame retardants and blowing agents. For spray foam there are also indoor air quality concerns. While the base material is relatively benign, the chemical agents that set the foam can take months or years to dissipate and if curing does not go perfectly a toxic environment will persist. 

For the Spring Street Passive House, we set a goal to be intentional in the use of foam building materials generally, and to avoid spray foam completely. Our commitment led us to a suite of materials that are better for both people and the planet. We designed a double-stud wall system that allows us to insulate with dense-pack cellulose, made from recycled paper. For our continuous exterior insulation, we're using mineral wool, a vapor-open material made from spun rock and slag. These choices drastically reduce the building's embodied carbon and eliminate a significant source of potential indoor air pollutants. 

Is it 100% foam-free? Not quite. There are small, targeted applications where we chose foam. For example we have 4” of GPS for slab insulation. Within the home, our hydronic lines are manufactured within a layer of foam for insulation and structural integrity.