Enertia Sustainable Home

I would like this to be our next home.



In the Enertia® Building System, solid Energy-Engineered(tm) wood walls replace siding, framing, insulation, and paneling. An air flow and access channel, or Envelope, runs around the building, just inside the walls – creating a miniature biosphere. Here solar heated air circulates, pumping and boosting geothermal energy from beneath the house, storing it in the massive wood walls. Thermal inertia causes the house to “float” between the cycles of night and day, and even between the seasons.

Many aspects of the Enertia® House are unusual and innovative – but backed up by science, common-sense, and prototype homes across America. In fact, each aspect listed below increases the energy efficiency of the building. The effect is Synergistic – equal to more than the sum of the parts. The Enertia® House can make more energy than it uses!


     In 1981 the National Institute of Standards and Technology constructed six test buildings in Gaithersburg, Maryland and tested them for energy efficiency. Much to their surprise, Building 5, with walls made of solid wood, was the most energy efficient. This was attributed to “thermal inertia,” a phenomenon where the solid wood walls stored energy during the day, and released it during the night. Actually the energy efficiency of solid wood is well known in the Scandinavian countries where it is the prevalent method of building. (Its long life is well known too. When interviewed during the 1994 Winter Olympics, a Lillehammer couple casually remarked that their solid wood home had been built in 1406!)


     There is no logical reason to use a drop of fuel, or a watt of energy, to heat or cool any home or building attached to the Earth. Just below the surface, within reach of the average basement, is an infinite reservoir of heat that never drops below 50 degrees F. The night-day cycle is more than ample to raise that temperature into the comfort zone, with a simple shift in Time. The use of daytime heat at night, and nighttime cool by day, is made possible by Thermal Inertia, and the engineered Lag-in-Time is a property of the thickness and Specific Heat of the solid wood walls.



The task of extracting useful heat from the geothermal reserve or outside air is usually relegated to the electric Heat Pump. They have been tacked onto homes by the millions – encouraged, even financed, by the electric utilities. You have seen them – noisy, power-hungry, CFC-filled, life-support machines – hanging off the side of an obviously troubled building.

Our solution, in the Enertia® Building System, is to make the house itself a heat pump, using the natural energy of rising solar-heated air to extract and enhance the pool of geothermal energy just beneath the building’s floor. Simple, foolproof, no CFC’s, no electric bill (see “Heat Pump House,” Popular Science, June 1992, p.42).



     Just how does a house, or office, or any ground-based structure get turned into a natural energy machine? The secret is an air path, or “Envelope” just inside the structure’s solid wood skin. It is a heat path on a sunny Winter day, a continuously recharging convection loop. A heat source, and extra insulation for a cold Winter night. A miniature biosphere, oxygenated by Sunspace plants. A fresh air-to-air exchanger with walls that breathe. A buffer zone to noise, wind, and outside pollution.

     It is a ventilation path on the hot Summer day and on the cooler Summer night, when it is open to the atmosphere. It is the dehumidification system when its permeable outer wall is hit by the sun. And always, an access channel to otherwise unreachable parts of the house when it comes time to update, add new wires, cables, pipes, or technology.


     The Enertia® House works because the walls have the ability to gain, hold, and release heat. They do double-duty as structure and storage. Their thermal mass and thermal lag leads to “Floating,” where stored daytime energy cancels out night-time need. Floating can last for days, keeping the house comfortable during periods of little or no sun. Massive houses experience seasonal “Float” as well, and can coast a month or longer when lightweight houses need artificial heating or cooling. Enertia® Houses float right through heat waves and arctic blasts that would endanger occupants of other buildings. (“Floating,” Abstract: A Field study of the Effect of Wall Mass on the Heating and Cooling loads of Residential Buildings, Doug Burch, et. al. National Institute of Standards and Technology, 1982)


    All architects and engineers work with the Heat Loss Equation. Heat loss equals the temperature difference (Delta T) divided by resistance (the familiar R factor). All modern attempts at energy efficiency have focused on the “R” factor – i.e. more and more insulation into a thicker wall. But reducing Delta T has the same effect – why not look at that? While insulation is necessary to increase “R” factor, Delta T can be reduced by natural means. The Envelope presents an entirely different Delta T to the living space than it would see if the house were single walled. Because of it, the living space never “sees” conditions colder than the geothermal temperature under the house! As the sunshine raises the Envelope temperature in the closed Wintertime loop, Delta T goes to Zero, and “R Value” is meaningless. At this point the Enertia® house is in equilibrium and Heat Loss = 0.


    The ultimate in heating and cooling, radiant walls and floors are inherent in the Enertia® Building System. When your feet are warm, you feel warm all over. It is efficient, dust free, even heat – more healthy and invigorating because the air you breathe is cooler. On the coldest Winter day, the Envelope keeps the North wall warm and you can lean up against it. Try that in a conventional house.



     The same thermal mass that acts as a heat source in winter becomes a heat sink in summer, again enabling an energy-shift- in-time. The envelope is opened to the outside for summer cooling – basement windows for intake, rooftop windows for exhaust. Natural ventilation carries off internal heat captured by the massive walls during the day. The permeable walls allow humidity to migrate towards the outer surface where it is evaporated by the sun. Because of the envelope, the house is wrapped by the cool in-ground climate. (The House that Needs No Fuel, Architectural Designs, August, 1988, p.6)


     Finally, we like our houses and offices in all shapes, forms, finishes, colors, and styles. This is why Enertia® is more than houses – it is a building System. While we have a catalog of standard, proven plans – fully half our production is custom – working from owner sketches and architects’ plans. We feel that you should get what you want in a house that you will live and work in and never want to leave.

Want to know more? Check the Source List for some of the sources consulted in design of the Enertia® Building System



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