Santa Fe Habitat for Humanity is asking its volunteers to do something different this week and invites the public to come watch. Instead of hammering the wood with hammers and nails, the organization will stack hollow blocks of concrete insulating forms.
When lumber prices soared 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 to use in 16 locations across the country. . Santa Fe has been chosen and two houses will be built in the village of Oshara with the materials from Monday.
Santa Fe is a market with a long history of using insulating concrete forms for exterior walls. At the start of the green building movement, the main focus was not on energy and water conservation. It was “saving the trees”. For this reason, the ICF have gained a foothold here.
This establishment was firmly anchored with the advent of Las Campanas at the end of the 1980s. One of its construction pacts: the glass surfaces of the windows had to be set back at least
4 inches from the plane of the exterior stucco so that it looks like thick adobe walls. This requirement has 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, tied together with plastic ties. Block sizes vary by manufacturer, but 16 inches high by 4 feet long and 10 inches wide are typical. A person can easily pick one up and stack it on top of each other, which means the exterior walls go up very quickly.
Once the forms are stacked to the desired height (8-10 feet) and window and door openings are blocked, a concrete pump pours a soft concrete mix from above. Concrete flows horizontally and vertically, filling tubular cores 4 to 6 inches thick. If the foam were removed, which is not the case, we would see a network of concrete tubes. Reinforcing steel bars are embedded in the concrete to add strength.
As the green building movement evolved, some began to express concerns about the intrinsic energy inherent in expanded foam products like styrofoam and in the manufacture of cement. These concerns still exist, but there is no doubt that an ICF structure is strong and energy efficient. The walls are virtually soundproof and have none of the air leaks associated with even well-constructed frame walls. With drywall attached on the inside and cement stucco on the outside, they are also very fire resistant.
Because the walls are double the thickness of standard frame construction, there is a sacrifice of interior space. In a 1,200 square foot home, this could represent a loss of up to 100 square feet.
Habitat volunteers won’t be putting away their nail pouches anytime soon – interior walls and roofs are still being built as they always have been, but this week’s double construction could point a new direction for our local chapter of Habitat.
Kim Shanahan has been a Santa Fe green builder since 1986 and a sustainability consultant since 2019. Contact him at [email protected]