Spray foam: buyers beware
September 8, 2020
Indoor health, planning a renovation, resource efficiency
Polystyrene spray foam has become the industry standard for home insulation. Usually contractors love it because of its high insulation value and low permeability, which eliminates the need for an air barrier. It’s a two-in-one solution that gives homeowners an easy and affordable option for energy improvement at a glance.
But “easy and cheap” will only get you so far. Unfortunately, this industry standard can create several problems across the board that are expensive and can affect indoor air quality.
The problem starts when a contractor doesn’t apply construction science to the project. This approach is essential when renovating the older Toronto homes, whose uninsulated walls have many gaps and are far from airtight.
This does not mean that we cannot safely improve the energy efficiency of a centuries-old home. We just need to consider suitable wall assemblies. Spray foam is rarely the most appropriate choice.
Here’s why. At least 5 cm of spray foam, as required by the code, on brick walls significantly affects the vapor permeability. Steam carries moisture. Nowhere can moisture be trapped in the brick. Over time, due to sun-induced moisture and freeze / thaw cycles, this moisture can weaken the brick and mortar joints and lead to costly repairs.
Insulation is important, but it is only one aspect of energy retrofitting. Proper airtightness and mechanical ventilation are also required to ensure energy efficiency, durability and good indoor air quality. Retrofitting work must view the house as a complete, interconnected system.
I’ve seen houses that were hermetically sealed for energy efficiency reasons, but without thinking about the need to remove stale, damp indoor air. Without HRV, mold grew on the walls where the furniture was placed due to the lack of airflow.
While mold can be toxic, spray foam can also be toxic. First, it is literally made in your home. During installation, two liquid chemicals are mixed on site. This must be done by a certified professional wearing appropriate personal protective equipment. Homeowners must be out of the home for at least 24 hours. Second, if the spray foam is not mixed properly when used, which happens too often, the foam can continuously degas. Health effects include breathing problems, headaches, and eye / throat irritation.
“If you don’t want to play Russian roulette at home, we recommend not using spray foam,” writes 475 High Performance Building Supply. I couldn’t agree more.
While spray foam can be a great insulator, its “embodied carbon” is very high, which has a negative impact on attempts to counter global warming.
Construction specialist Chris Magwood has studied the size of embodied carbon, which he defines as “the total greenhouse gas emissions from harvesting, transporting and manufacturing building materials”.
According to Chris: “It is estimated that up to 11 percent of global emissions come from the manufacture of building materials! While efficiency is important, reducing material emissions is immediate and therefore more effective in reducing atmospheric carbon concentration now rather than in the future. “
Fortunately, low carbon insulation and other building materials are available. A vapor open wall assembly that contains low carbon insulation and is vapor permeable provides a safe alternative to installing spray foam.
This article originally appeared in Neighbors of High Park Magazine.
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