During Week 3, we built floors for the two homes on pilings and laid radiant floor tubing. The homes will have concrete slabs and and about 10 inches of under-floor spray foam insulation.
Two of the homes will have insulated raft foundations. This allows the house to rest directly on the ground, keeping the floor warmer than if it were elevated on piles. A thick mat of spray foam is designed to prevent heat loss from affecting the frozen ground, and a cooling system was also installed in the gravel pad to chill the soils if needed.
CCHRC is demonstrating an innovative foundation design at the Sustainable Village. Two of the homes, sitting on permafrost about 9 feet deep, will be built on steel piles, a common method for building on frozen ground. The other two, situated on stabler soil, will have an insulated mat foundation.
Builders laid the mat foundations last week. They include a geotextile mat placed directly on the soil with several feet of gravel on top. PVC pipes are embedded in the gravel in a grid formation as a backup cooling system. Resting on the pad is a steel floor assembly. Spray foam was applied against the entire system for a monolithic layer of insulation at least 10 inches thick. This is designed to prevent heat from inside from transferring to the ground. Temperature sensors were strung about 10 feet down into the soil to monitor any changes. If needed, cold air could be circulated through the piping system in the winter to lower the temperature, as insurance against shifting ground.
Here’s a look at the pad preparation.
The UAF Sustainable Village broke ground on Friday, April 6 on lower campus near the Cold Climate Housing Research Center.
The development will feature innovations in cold climate construction—with super-insulated building envelopes to minimize heat demand—as well as experimental approaches to energy, ventilation and wastewater treatment. The homes will serve not just as student residences but also as housing prototypes, building science labs, and teaching tools.
UAF students helped CCHRC develop the concept for the homes, through a design contest, and will help build and conduct research on the Village as well.
“The thing that’s unique about this project is it’s engaging students for the first time in the development of sustainable housing,” said Michele Hébert, who heads the UAF Office of Sustainability. “Our hope is that this will lead to more young people learning how to live sustainably and be future leaders in sustainability.”
The 1,500-square-foot homes will have an R-50-60 envelope and will use a mix of solar, biomass and conventional fuel. A 14 kw photovoltaic array was funded by the university sustainability grant.
The project will demonstrate that a highly energy efficient 4-bedroom home can be built in Fairbanks without breaking the bank. The budget is approximately $200,000 per home. The rent will approximate the cost of a mortgage for an equivalent new single-family home in Fairbanks and be competitive with dorm rates.
Construction will be done by seasoned carpenters along with UAF student workers. Student residents move in in mid-August, so we will be busy for the next few months!