Light Clay-Straw & Solar

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Hal & Allison's home
Hal Brill and Allison Elliot’s light clay-straw home brings together passive solar design, active solar technologies, natural materials, and an efficient layout for an energy-saving, durable dwelling.
The home and garage
Before the home was built, the garage was constructed and a grid-tied PV system was installed. The solar electricity that was generated (and credited to the utility account) offset electricity consumed during the home’s construction.
Home Interior
Natural materials­—­from the tongue-and-groove ceiling to the natural clay walls and floor—are cornerstones of this home’s design.
The solar collectors behind the house.
Solar collectors, which provide water and space heating, are ground-mounted on the north side of the house.
The clay-straw walls under construction
The infill clay-straw walls need ample time to dry before receiving exterior and interior finishes.
Faswall block foundation
The foundation was built with Faswall blocks that consist of concrete-coated wood chips with rock-wool insulation inserts.
Low U-factor windows
All windows have a low U-factor; south-facing doors and windows have a high solar heat gain coefficient (SHGC).
Hydronic tubing going in
Hydronic tubing was laid over the insulated subfloor.
Adobe clay covers the hydronic tubing.
Hydronic tubing was covered with three inches of adobe clay, which serves as the floor surface.
The PV array
The 2.94 kW grid-tied PV array provides all of the home’s electrical energy needs.
The system inverter and distribution box
A single inverter (left) supplies a distribution panel (right) tied to the utility grid and to household loads.
The picture windows
Lots of glazing on the house’s south face allows the low-angled winter sun to warm interior spaces.
The solar thermal collecotrs
Four 4-by-8-foot collectors provide hot water, which is distributed for domestic use and space heating, and to a hot tub.
Hal & Allison's home
The home and garage
Home Interior
The solar collectors behind the house.
The clay-straw walls under construction
Faswall block foundation
Low U-factor windows
Hydronic tubing going in
Adobe clay covers the hydronic tubing.
The PV array
The system inverter and distribution box
The picture windows
The solar thermal collecotrs

Hal Brill and Allison Elliot’s light clay-straw home brings together passive solar design, active solar technologies, natural materials, and an efficient layout for an energy-saving, durable dwelling.

Home Power (HP): Besides incorporating solar technologies, your home has some unique features. What served as your initial inspiration?

Allison Elliot: The development process took several years. Key inspiration came from architect Michael Frerking’s house that was featured in a 2005 issue of Sunset magazine. We fell in love with the curved roof, and that really landed the design for us.

The overall design is dominated by this curve, which evokes Anasazi cliff dwellings and our experiences in the canyons of Utah on raft trips. Our front hall is like a slot canyon—narrow, curving, and emerging into the larger space of the living room. Like a slot canyon, the light you see ahead draws you forward. The walls of our guest and music room—what we call the “flex” room—are of red clay plaster called Bryce Canyon, as if it were the darker, deeper part of the cliff dwelling.

HP: Why did you decide to use clay-straw (or “light-clay”) as the wall infill material?

Elliot: Through the years, we attended numerous sustainable building conferences, including the International Straw Builders Conference. We were drawn to the idea of straw bale, having had friends who went that route, but we were also intrigued by clay-straw.

Hal Brill: We were fortunate to be able to tour two clay-straw homes in our area and to see how they performed in both summer and winter. Paonia has large temperature swings—climbing above 90°F in the summer and dipping below 0°F in the winter. We wanted something with enough thermal mass to handle those swings.

Clay-straw seemed to be the middle ground. It offers more thermal mass than straw bales but not as much as traditional adobe. There are no voids, and burrowing insects or rodents aren’t an issue. Clay-straw walls are also thinner—12 inches versus 18 inches for straw bale—meaning that for smaller building envelopes, you gain more square footage. The thinner walls also enable using a narrower footing, saving on material and costs (see “Building with Clay-Straw Walls” sidebar).

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Comments (1)

Anonymous _2267's picture

I'm intrigued by the "steamback" solar fluid expansion control. You can have a pressurized ( 25-30 lbs ) solar fluid circuit that can handle stagnant fluid in the collectors ( not turn to steam ) with a small expansion tank and of course drain back systems. This "steamback" system must have a hugh expansion tank to handle the pushed out solar fluid and some steam pressure. Perhaps the installer ( Clean Slate Energy ) can comment more about this such as what size expansion tank for a given amount of solar fluid John Nelson--Nucla, CO

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