Innovative Details

The Affordable Natural House incorporates a number of innovations. One is the roof ventilation system. Ours provides passive cooling as well as an inexpensive "faux-cold roof" feature designed to eliminate problems of roof leaking due to ice damming that is common in the Upper Midwest.

roof framing without decking

"Cold Roof"
True cold roof design avoids leaking caused by melting snow & ice. It uses double roof decking, separated by extra framing and vented to make sure the 'outer' roof stays cold. It works well but it's expensive. Our low-cost "cold roof" design is created using house wrap material. The sheets are formed into channels between the roof trusses and stapled into place. The deep channels create an oversized vent space, and also maintain the correct depth for easy installation of the cellulose roof insulation.

House wrap material allows water vapor to pass through, permitting the insulation to ventilate and stay dry. But house wrap sheds liquid water. So if the roof ever leaks through the shingles, water will run harmlessly down the house wrap and outside via the vent screens at the bottom of the channel.

deep channels for venting and leak protection

Passive Cooling
The passive cooling system is adapted from research in the 1960's by the Illinois Small Homes Council, before central air-conditioning systems were commonplace in homes. That investigation sought to answer the questions, "Can summertime attic temperatures in the Midwest be lowered significantly via natural (non-fan) ventilation, and if so, how much ventilation would be required?"

Using full-scale testing, researchers concluded that oversized ventilation (at least 6 times the code-minimum) could keep an attic 10 to 15 degrees Fahrenheit lower than conventionally vented attics. The result is less heat penetrating into the living space, and greater comfort. Click to see a diagram of how our ventilation system works.

big skylight over balcony

Solar Heat and Fresh Air
Big skylights for passive solar heating are not an innovation, nor is moving insulation, indoor gardening and computer automation. But we are combining these elements into an integrated system to heat, cool and freshen the indoor atmosphere.

Some features include:

  • A "balcony garden" under a large south-facing skylight to absorb carbon dioxide and provide fresh, oxygenated air
  • Clear, non-low emissivity skylight glazing, for maximum solar heat transmission and to provide plants with as close to natural light as practical
  • Summer "scrim" that allows sunlight to reach the plants while keeping hot air out of the house and vented away to the attic
  • Moving panels under the skylight that insulate nearly as well as the main roof, to minimize nightime heat loss
  • Insulation panels opened and closed by a computer automation system that knows sunrise & sunset times throughout the year and can compare indoor & outdoor temperatures. The computer will be an old recycled model, of course.
  • The balcony garden will incorporate a self-regulating watering system using collected rainwater, as developed by Dr. Wes Jarrell.

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