Posted Aug 12, 2022 11:04 a.m.
Amid global climate change and a chronic shortage of affordable housing, local construction companies and nonprofits are taking innovative steps to make homes more energy efficient and environmentally sustainable.
Strata International Group, headquartered in Phoenix, has made a name for itself building foam and concrete homes, and Habitat for Humanity of Central Arizona has successfully print a 3D house for a Tempe family – the first structure printed in Arizona.
These energy-efficient and affordable materials and techniques come at an opportune time. A 2018 National Low Income Housing Coalition study
reported a shortage of more than 7.2 million rental units for low-income tenants, and a 2019 report by the International Energy Agency and the United Nations Environment Program found that the construction industry accounts for 39% of energy-related carbon emissions.
The foam house
To form the structure of a house, Strata uses a system called SABS, which uses expanded polystyrene foam similar to polystyrene foam. The foam is shaped, the forms are glued together in the walls, ceilings and floors, then coated inside and out with a layer of the company’s special concrete mix, called Sabscrete. It holds everything together, protects the foam from impact, weather and fire, and allows the surface to be painted and textured. No wood or steel is used.
“These homes are built to last 300, 400, 500 years,” said Amir Saebi, executive director of operations at Strata, adding that the foam acts as an insulator, which means it takes less energy to cool or heat homes. This benefits both homeowners and the environment.
Contractor Kenneth Skinner, who uses SABS to build his personal home in North Phoenix, expects the solar panels he is installing on the roof to meet all of his energy needs with foam insulation.
Because SABS uses no wood, it’s a big cost saver in a time of supply chain issues and inflation.
“It was going to cost me between $35,000 and $40,000 more…because of lumber prices,” Skinner said. “So that’s just when I was introduced (to) Strata, and so I saved that money.”
Skinner builds his house with only a few workers; Saebi said some builds can have as few as three workers, since construction is less intensive because workers only have to move large slabs of foam and Sabscrete mix.
But it’s not entirely eco-friendly, as Saebi acknowledged. Expanded polystyrene foam is made from petroleum waste, he said, but that impact is offset because the houses are expected to last for centuries – far longer than contemporary wooden houses.
The printed house
Habitat for Humanity took another approach to affordable and sustainable homes: a giant 3D printer.
The equipment applies thin layers of concrete, one on top of the other, until a full wall or frame is erected, then workers pack insulation into the space between the layers of the wall. After the exterior and interior walls are completed, the floors, ceilings and fixtures are completed using traditional construction techniques. Habitat for Humanity estimates that 70-80% of the 1,738-square-foot, three-bedroom home has been printed.
It’s the first 3D-printed home built by the nonprofit — and the first in Arizona — and the idea came from two ASU sustainability graduates. Habitat officials say they can’t calculate the exact cost of the project because most of the materials have been donated, but they hope to use this technology to build more at a lower cost.
3D printed homes are more energy efficient than traditional homes because concrete and tightly packed insulation maintain internal temperatures.
“We heard from the family (who live in the house) that the air conditioning doesn’t really work that much,” said Dusty Parsons, marketing director for Habitat for Humanity. “When it is, it’s only on for a few minutes, the house…stays very, very cool because it’s a solid double wall of concrete with foam insulation.”
The printer, made by the German company Peri and donated by it for use in this project, is supported by metal pillars and moved around the site on computer-controlled sliders.
Cronkite News Reporter Jessica Herrera contributed to this story.
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