Thorntree Commons at Suttons Bay
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WHO WE ARE
THORNTREE GUIDELINES
MASTER DEED & BYLAWS
THORNTREE SITE PLAN
LEED AND SUSTAINABILITY
PRESS RELEASE: 3/13/06

Conceptual Designs

OPEN LETTER TO ARCHITECTS
DESIGN: JANA K. VANDER GOOT

Articles

WHY BUILD GREEN?
TEN PRINCIPLES
DR. JONG-JIN KIM: EXCERPTS
A VISIT TO TRYON FARM
LETTER FROM HANNA DONIGER
A SOLAR ENVELOPE HOME
HYBRID HOMES
CONSIDERING LEED FOR HOMES

Lois Bahle's Solar Envelope Home


I almost hate to admit it, but my cousin Lois Bahle was years ahead of me in thinking very specifically about what we can do to provide beautiful shelter, live well and very comfortably, and make a difference for the planet. Last year sometime I asked her, "What if, dear cousin, since you live in the wooded hills above the village in a very sustainably designed home only a few hundred yards away from Thorntree, I were to do a story about your house?" Almost before I finished the sentence, Lois was reaching for the "history of the house" with its reams of text and photos and articles. She didn't take a casual approach to her housing project.

I have visited Lois's house on numerous occasions, often with friends. I've found that seeing her home often helps people to imagine an envelope house at Thorntree, to give people a concrete example of what is possible and successful and beautiful, in virtually the same setting as Thorntree. Their verdict is unanimous: this is truly a wonderful living space and it works.

We also have the benefit of time and improved materials and techniques. We can not only make use of Lois's experience, but in terms of material efficiency we can greatly improve upon it. When Lois's home was built in 1982, its energy efficiency exceeded 99% of what home builders were doing. Even so, it would not currently be classified as a super-insulated structure. Today one could build a home exactly like Lois's but increase the insulation value by more than double. The energy loss factor would be improved enough to make it well worth the investment.

There are many ways to create a considerate and beautiful home and thanks to the thoughtful and meticulous contribution of my cousin, we have a chance below to "visit" one of them.


My interest in conserving began with the energy crisis of the mid '70s and the restoration of a house in Grand Rapids, Michigan. I charted the change in energy costs as the house was updated with new windows, insulation, timers on water heaters and set back thermostat. When the opportunity arose to move back to my family home in Suttons Bay, I had the dream to build a new house with the best practices for energy conservation available at the time. My aim was to avoid high utility bills and equipment maintenance. It was important that the construction would preserve natural resources and be built using conventional materials and skills.

I was inspired by Lee Porter Butler's "Ekose'a" home designs. Butler began design work on his concept house in 1966. It was to be located in Tennessee, where winter can be cold with below zero temperatures and where there are long periods of cloudy weather. The aim was that it would be simple and economic to build, and require minimal dependence on outside power or fossil fuel for heating and cooling. This led to the consideration of solar energy. At the time, solar applications were elaborate fabrications and costly. Instead, he proceeded to design a house in such a way that the structure itself performed as a solar collector and storage system, incorporating a buffer zone between the house and cold outside air. This system became known as a "Solar Envelope."

So how does my Solar Envelope home work? The entire south side of the house is a sunspace, a two-story living space dedicated to gathering solar energy. As I've mentioned above, there are no expensive solar cells involved; the building itself is actually a sort of passive solar cell. Air is warmed in the sunspace, then rises and passes through an attic plenum (air-filled space), down a plenem in the north wall, through the crawl space and back through the sunspace. The plenums extend the full east to west length of the house and are, in effect, an "envelope" buffering the house from extremes of outdoor weather. During the summer, the excess heat from the sunspace is vented out of the peak through gable vents, helping to ventilate the house. The house is sited 15 degrees east of due south to pick up more of the rising sun's warmth and is in full shade during the summer in deciduous woods.

Since '82 I've installed new Pella windows with argon gas, and I can see the improved performance. There is a vapor barrier under the drywall in the bathrooms. The roof is 1/2 inch plywood over the rafters with 3.5 inches of thermax (a foil covered foam material), spacers over the rafters for 1/2 inch of air and another layer of plywood, felt and shingles for a total cold roof over the house. I found that it's always best to avoid dormers and valleys in roof construction as that's where ice forms. It can be difficult to get cross ventilation during summer heat with the limited windows on the east and west ends and none on the north side, but this could be easily solved in a new home today by including a whole house fan.

I use about 5 cords of wood for heat each year at $60 per cord. The 324-square-foot office space is heated by an electric baseboard, and there are electric baseboards in each bathroom and in the 81-square-foot air-lock entrance. The air-lock can be set to run at 40 degrees to protect the laundry located there from freezing in extreme temperature times. I have my own well, and the water heater is electric. The average electric usage per year seems to run about 11,000 kwh. The garage is 530 square feet. The entire house, including the sunspace, is 2,150 square feet.

To arrange a personal tour, Lois can be reached by email at loisbahle@centurytel.net.