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Montana Green Power

Your Guide to Renewable Energy in Montana


Ennis Pyramid House Takes Advantage
of Active and Passive Solar, Plus Wind

Whitney Lake’s Pyramid House near Ennis incorporates active and passive solar features, along with a small wind-energy system. The distinctive off-the-grid structure was built and furnished with an eye to energy efficiency and conservation.

Three first floor walls and all four faces of the pyramid are made of R-Control Panels manufactured by Big Sky Insulation of Belgrade, Montana. The panels are constructed of 10.5-inch and 12.5-inch expanded polystyrene sandwiched between two sheets of osb (oriented strand board). "They have excellent insulation qualities, boasting an R-value of between 39.88 49 at 40 degrees," says Lake.

A trombe wall on the south works by thermo-circulation. Lake explains how it works: "Cold air falls through vents in the floor; the south-facing concrete (painted a dark color) is heated by the sun; the warmed air rises and is vented to the living space. Cooled air falls and begins the cycle again." The glass front was installed by Valley Glass of Bozeman, Montana.

A Helio-Pak 16, made by Heliodyne, Inc., is another passive solar feature. It uses a glycol-distilled water solution that circulates via a photovoltaic controlled pump. 

"The warmth of the radiating sun does the work," says Lake. "The heat is transferred in a loop to bring well-temperature water up to 80-120 degrees."

He generates electricity using the sun and the wind. His solar array includes Siemens and Kyocera photovoltaic panels that produce 1180 watts/hr during peak insolation hours. 

A Bergey Wind Turbine, designed to withstand winds up to 120 mph, produces 1750 watts/hr in 35 mph winds. "The three blades are extra stiff for severe weather resistance," says Lake.

Take an online tour of the house. 

Photos courtesy of Whitney Lake.


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