Frank Slater, KP News
One of two new Habitat for Humanity houses at Palmer Lake is being built to be energy efficient. The Russell Family Foundation gave a $10,000 grant to help fund this project, with the provision that it be “green.”
The centerpiece of this effort is a Wirsbo radiant heating system. The heating unit is a propane-fired demand water heater, which also provides hot water for household use. It turns on when a hot water faucet is opened, or the house temperature falls below the thermostat setting. There is no hot water tank to cool off between times of demand.
The hot water is circulated by pumps through a manifold that regulates its flow, so rooms with higher demand get more heat. The water is carried through tubes fastened to the bottom of the subfloor.
Each joist pocket has its own loop of tubing. When this is in place, insulation is put in below it to keep the heat against the subfloor. The subfloor is the agent that carries the heat into the house.
Bob Delaney, chairman of volunteers for the Gig Harbor/Key Peninsula Chapter of Habitat for Humanity, said the initial cost of this type of installation is generally higher because of the labor required to install the tubing in each joist pocket. The cost would be offset by lower costs for energy. In this case, the costs were about the same because he has volunteer labor to do the installation. Delaney said his understanding is it would take about two years for lower energy costs to pay for the additional labor.
Joe Purdue, the plumber on site, estimated less than 100 watts of power are needed to circulate the water. This is about what it takes to operate one ordinary light bulb. The main amount of energy required is provided by propane, and any small generator should be adequate to operate the system in case of a power outage.
Purdue pointed out that with radiant heat there were only a few degrees difference between the temperature of the air at the floor and at the ceiling while with forced-air heating there might be a difference of as much as 30 degrees. He also noted that a large closet the plan called for as a mechanical room had been converted to a general-purpose closet, and a much smaller closet was to house the heating pumps and controls. This is an important consideration in a house this size.
The plan calls for, 15 to 16 inches of R-38 insulation to be blown into the attic, R-21 in the walls and the floor. The windows are insulated and have an area of less than one-seventh of the floor space. Even the shape of the house is energy efficient. It is 32-feet square with an area of 1,024 square feet. A rectangular house, 24 feet by 40 feet, would have the same amount of outside wall to heat but have an area of only 960 square feet, or about 8 percent less floor space.
Delaney said each house is planned individually. He does not know if future houses on the Key Peninsula will follow this energy efficient pattern.