SPECIAL SECTION
• Conserve water by reusing waste water for toilets and landscape irrigation.
• Reduce demand on city services, such as water supply, sewage and fire protection.
Lenberg and his wife occupied the home (see Figure 1) in October 2009. The three-bedroom, two-bath ranch-style home is slab-on-grade with 1,700 square feet of living space.
Green Features
Reduced environmental impact
Kozimor used finger-jointed studs for the wall framing. The studs are formed from odd lengths of studs that would normally go to waste. A machine notches “fingers” on the pieces and cements them into usable lengths. Figure 2 shows two sections of a finger-jointed stud prior to cementing.
The cement used for the concrete foundation also reduced environmental impact by using fly ash recovered from the Farmington electric generating plant.
Reduced energy costs
Farmington temperatures vary widely. Summer daytime temperatures can exceed 100°F and winter nighttime temperatures can drop below -25°F. Kozimor chose an insulation that primarily prevents radiant heat transfer. The insulation, called P2000, is flexible sheets of expanded polystyrene laminated on each side with a thin layer of metalized plastic. The sheets come in thicknesses of 3/8 to one inch. The product primarily reduces radiant heat transfer, which accounts for about 50 percent of heat gain and loss between interior and exterior spaces. The product also reduces conductive heat transfer (around 45 percent of heat gain and loss), as well as convective heat transfer (around five percent).
Figure 3 illustrates how the insulation works. The interlocking sheets cover the entire exterior of the wall surface. Traditional insulation methods, such as placing batts of insulation in the wall cavities, leave the studs exposed. Exposed studs, along with window and door framing, can take up as much as 20 to 30 percent of the wall space and account for a lot of conductive heat transfer.
As Figure 3 shows, the P2000 panels cover the studs and other wood framing, which reduces conductive heat transfer. The metalized plastic on the sheets also reduces convective heat transfer.
The insulation is not limited to the walls, but envelops the entire home. The envelope begins under the floor slab, extends up the walls and over the roof framing. The floor slab and wall insulation is 3/8 inch and the roof insulation is one inch.
Figure 4 shows the insulation installed beneath the concrete pad, and Figure 5 shows it installed over the roof framing.
After moving into the home, Lenberg has recorded exterior and interior temperatures on a daily basis. His recordings during extreme weather conditions demonstrate the insulation’s effectiveness. On one of the hottest days of the year, July 15, 2010, the outside temperature registered 106°F. The home does not have air conditioning, so insulation is the key factor in maintaining a comfortable interior environment. The temperature in the living areas was 78°F and the attic temperature was 80°F.
The home and garage are heated throughout with hydronic radiant floor heating. Radiant-floor heating is more efficient than other methods, such as forced air. In this home, the builder made it even more efficient by heating the water with solar thermal panels (Figure 6). The water in radiant floor heating systems is normally heated by electrically powered boilers. A home of Lenberg’s size would require a 20kW boiler. By heating the water with solar panels, Kozimor eliminated the 20kW boiler and its higher operating costs. In its place, he installed a 2kW boiler that augments the solar panels during hours of darkness.
Figure 1. Lenberg home.
Figure 2. Finger-jointed stud.
Figure 3. P2000 insulation forms an exterior envelope over the entire wall surface.
Figure 4. P2000 installed under the hydronic heating tubes in the floor.
Figure 5. Roof framing covered by P2000 insulation.
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