Santa Fe Habitat for Humanity urges its volunteers to do something different this week and invites the public to come and watch. Instead of hammering wood together with hammers and nails, the organization stacks hollow blocks made of insulating concrete formwork.
As wood prices skyrocketed earlier this year, Habitat for Humanity International was approached by the National Ready Mix Concrete Association and the Insulating Concrete Forms Manufacturers Association with an offer of free material for use in 16 locations across the country. Santa Fe has been chosen and the material will be used to build two houses in the village of Oshara starting Monday.
Santa Fe is a market with a long history of using insulating concrete molds for exterior walls. In the early days of the green building movement, the focus was not on saving energy and water. It was called “Save the Trees”. For this reason, the ICFs have established a strong pillar here.
That mainstay became more solid with the advent of Las Campanas in the late 1980s. One of his building contracts: the window panes had to be reset at least
4 inches from the level of the exterior stucco to resemble thick clay walls. This requirement prompted many builders to experiment with ICF exterior walls.
A typical ICF block has 2 inches of foam on each side of a hollow core that is joined together by plastic straps. The dimensions of the blocks vary by manufacturer, but 16 inches high, 4 feet long, and 10 inches wide are typical. One person can easily pick them up and stack them on top of each other so that the outer walls are pulled up very quickly.
Once the molds are stacked to the desired height and window and door openings blocked, a concrete pump truck pours a soupy concrete mix from above. The concrete flows horizontally and vertically, filling tubular cores 4 to 6 inches thick. If the foam were removed, which it wasn’t, you’d see a grid of concrete pipes. Reinforcing steel bars are embedded in the concrete to increase strength.
As the green building movement evolved, some raised concerns about the energy contained in foam foam products such as styrofoam and in cement making. These concerns still persist, but there is no doubt that an ICF structure is solid and energy efficient. The walls are practically soundproof and have no air leaks that occur even with well-built frame walls. With drywall installed on the inside and cement-based stucco on the outside, they are also very fire-resistant.
Because the walls are twice as thick as a standard frame construction, the interior space is sacrificed. In a 1,200 square meter house, that can be up to 100 square meters in loss.
Habitat volunteers won’t be putting their nail pockets away anytime soon – interior walls and roof structures are still being built as always, but this week’s double build could open a new avenue for our local habitat chapter.
Kim Shanahan has been a Santa Fe Green Builder since 1986 and a sustainability consultant since 2019. Contact him at [email protected].
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