Energy-saver homes

September 23, 2009

By Drs. Robert & Sonia Vogl

President and Vice President

Illinois Renewable Energy Association

With 40 percent of our nation’s primary energy use occurring in buildings, residences are an important target for energy savings.

Bill Miller and his colleagues of the Oak Ridge, Tenn., Energy Lab will examine the performance of four new homes over a two-year period with the goal of achieving 50 percent reduction in energy used in heating, cooling and electrical consumption. Energy Star appliances will be used. The homes will be unoccupied to remove variables associated with patterns of different families.

Some new materials and unique approaches include using roof deck panels with a thin metal foil layer covering the interior to reflect solar radiant heat and prevent it from entering the building. A reflective material on the surface of asphalt shingles or a tile or metal roof can serve a similar role. Uniquely, the coatings enhance reflection, whatever the color of the roof.

Three lines of high-density polyethylene tubing carrying a 20 percent solution of ethylene glycol will be laid outside foundation walls and pass into a heat pump for heating and cooling. A rainwater catchment basin fed by roof runoff will facilitate the exchange of heat between the fluid and the ground. It should provide dramatic savings in the cost of installing a heat pump.

The 2-ton unit is half the size of a system normally serving a house of this size. R20 wall insulation, R30 to R50 roof insulation and triple-pane windows all reduce energy needs and equipment size.

Two of the homes will be two stories with walk-out basements, cathedral ceilings and no attics. One will be built of structurally-integrated panels (SIPs) and the other with advanced framing. Both basements will have slab floors with insulation and a vapor barrier under the floor to prevent heat loss to the ground. The exteriors of concrete basement walls will be covered with asphalt-based waterproofing and 2 3/8-inch fiberglass insulation. The other two homes will have crawl spaces and feature dynamic insulation or exterior insulation finishing.

The SIP technique uses large sheets of panels composed of two layers of chip board with a layer of phenolic foam insulation sandwiched between.

The optimal value framing system has 2-by-6 wall studs on 24-inch centers to save lumber. Using SIP-based phenolic foam insulation, the ceiling insulation is R50 while the wall insulation is R21. The exterior wall consists of OSB board with taped seams covered with a liquid-applied, weather-resistant layer.

The dynamic insulation approach includes phase change materials in blown cellulose wall and attic insulation to absorb heat during the day and release it back out at night. This home has a double 2-by-4 wall based on 24-inch centers with one row offset by 12 inches. The double wall has an R30 value. The inside wall is covered with gypsum board and the outside with 1/two-inch of weather-resistant strand board.

The ceiling insulation on the attic floor is equivalent to R38, but with the phase change material added it functions at an R75 rating under summer heat conditions.

The crawl space is ventilated and open to the outside air.

The exterior insulation finishing technique consists of 5 inches of polystyrene-based insulation attached to a stick-built wall of 2-by-4s set on 16-inch centers. The polystyrene layer insulates and keeps moisture out. A thin layer with an interior-facing reflective layer is attached to the insulation. The outside of this layer has a thinly-grooved surface that allows air or moisture to flow up and out of the wall.

The exterior surface of the walls is covered with cement-like base coat, reinforced with glass fiber mesh and coated with a moisture barrier. It can be left to appear similar to a stucco wall or covered with simulated brick, stone or traditional cladding. Nearly 80 percent of new commercial buildings use this wall method.

The crawl space in this home is insulated and not ventilated. A small amount of air from the air-conditioning unit will pressurize it to keep moisture out. The insulation layer is R6.

The results of this research will be used to produce a computer model to predict how the four approaches will perform across the United States.

(The preceding was based on a presentation at the Eighth Annual Renewable Energy and Sustainable Lifestyle Fair, Aug. 8-9, 2009.)

Drs. Robert and Sonia Vogl are founders and officers of the Illinois Renewable Energy Association (IREA) and coordinate the annual Renewable Energy and Sustainable Lifestyle Fair. The Vogls and the IREA are members of the Environmental Hall of Fame. Dr. Robert Vogl is vice president of Freedom Field, and Dr. Sonia Vogl is a member of Freedom Field’s Executive Committee. The Vogls consult on energy efficiency, renewable energy and green building. They have 3.2 kW of PV and a 1 kW wind generator at their home. Forty acres of their 180-acre home farm are in ecological restorations. They are active in preserving natural areas and are retired professors from Northern Illinois University. E-mail sonia@essex1.com.

From the September 23-29, 2009 issue

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