1st layer – closed cell insulation

After months of researching and weeks of preparations, the day has come to walk the walk.

A truck drives up and the insulation crew takes over the basement. Windows, doors and other materials and equipment get wrapped in plastic, the concrete floor is covered with tarps and a big old heated hose snakes it way into the basement. A spray gun is mounted to the hose and the fun begins.

The gray stuff that is sprayed onto the wall is the one inch layer of closed cell foam. It is the first of three layers in our insulation assembly.


The closed cell foam has a density of two pounds per cubic foot, and once cured is pretty rigid and stiff. It adheres tightly to the masonry wall. There are no gaps between the foam and the masonry, which is important. No gaps, no space for interstitial condensation to occur, and thus a very low risk for future moisture problems.

The one inch of closed cell foam has an R-value of 5.2. It delivers the all important air barrier, giving us an almost air tight building envelope. This prevents warm air escaping to the outside in the cold season and hot moisture laden air infiltrating into the living space at the height of summer.

Although the closed cell foam acts as an air barrier, it is not a vapor barrier. This product has a perm rate of 1.3 at three inches. With our one inch application, the perm rate will be greater than 1.3, which is important to us. It allows water vapor to pass through the wall assembly and as such keeps the drying mechanism intact.

It is not recommended to use spray foam before the moisture management of a masonry wall is resolved. Thus our eagerness to have had the parapet rebuilt, basement walls re-pointed and the brick around the bottom of the building replaced.

About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

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