Monday, April 14, 2008
This Solar House, Part One
In this two part feature, Norma and Alan Williamson explain in detail how they went about a zero-energy retrofit of their home, which saves money, energy, and the global climate.
Solar, Part 1 (Dec 2003)
We moved into our 2,300-square-foot house around Thanksgiving 2003. Within a month, in order to make use of state rebates that would decrease after the first of the year, we purchased a 6-kilowatt photovoltaic (PV) system. Installation occurred in two phases. First, in December, we installed the 4-kW array of 35 sapphire-blue PV panels that you can see on the south-facing side of our main roof; eight months later we added the 2-kW set over the garage (see "Solar, Part 2" below). This 6-kW PV system supplies all our energy needs, from our home's heating and air conditioning to the "fuel" for our electric car. (To learn how PV panels work, see Inside a Solar Cell.) Cost: $36,000 (6-kW system; after rebates and tax incentives totaling $17,500, our out-of-pocket expenditures came to $18,500)
Insulation (Jan–Feb 2004)
As part of our goal to make our home net-zero-energy—that is, generating more energy than is consumed—we set about improving our home's insulation. In January, we contracted a company to inject cellulose (recycled paper) insulation into the walls, bringing them up to an R15 level. (The R-value indicates the resistance of a material to the passage of heat and cold.) The following month, we replaced our leaky, single-glaze aluminum windows with dual-pane thermal windows. These are so-called "low-emissivity" windows, which keep winter heat in and summer heat out. We left our front picture window (behind car in main image and at left) intentionally non-low-emissivity, so the winter sun could warm our living room—a passive solar technique. Cost: $1,300 (insulation), $10,000 (dual-pane windows)
Roof (Mar–Jul 2004)
To further increase thermal resistance, we decided to replace the roof and upgrade our attic insulation. In March, we removed the 4-kW solar array as well as the existing, substandard roof tiles. The following month, we brought the attic insulation up to an R30 level. Then, in June, we installed aluminized solar sheathing on the roof. This is a thermal reflective plywood that keeps external heat out and reflects interior heat back in. We also installed roof jacks (to hold up the solar array) and then a new composite shingle roof. Finally, in July, we put in a whole-house cooling fan and whole-house heat-recirculating system (as well as two skylights, one seen in the center of the roof). The fan cools the attic and ceilings when outside temperatures are high, while the heat fan shuttles warm air from the attic to the ground floor when outside temperatures are low. Cost: $300 (attic insulation), $23 per 4' x 8' board (solar sheathing), $4,000 (new roof), $600 (whole-house fan), $570 (whole-house heater), $1,450 (two skylights)
Solar, Part 1 (Dec 2003)
We moved into our 2,300-square-foot house around Thanksgiving 2003. Within a month, in order to make use of state rebates that would decrease after the first of the year, we purchased a 6-kilowatt photovoltaic (PV) system. Installation occurred in two phases. First, in December, we installed the 4-kW array of 35 sapphire-blue PV panels that you can see on the south-facing side of our main roof; eight months later we added the 2-kW set over the garage (see "Solar, Part 2" below). This 6-kW PV system supplies all our energy needs, from our home's heating and air conditioning to the "fuel" for our electric car. (To learn how PV panels work, see Inside a Solar Cell.) Cost: $36,000 (6-kW system; after rebates and tax incentives totaling $17,500, our out-of-pocket expenditures came to $18,500)Insulation (Jan–Feb 2004)
As part of our goal to make our home net-zero-energy—that is, generating more energy than is consumed—we set about improving our home's insulation. In January, we contracted a company to inject cellulose (recycled paper) insulation into the walls, bringing them up to an R15 level. (The R-value indicates the resistance of a material to the passage of heat and cold.) The following month, we replaced our leaky, single-glaze aluminum windows with dual-pane thermal windows. These are so-called "low-emissivity" windows, which keep winter heat in and summer heat out. We left our front picture window (behind car in main image and at left) intentionally non-low-emissivity, so the winter sun could warm our living room—a passive solar technique. Cost: $1,300 (insulation), $10,000 (dual-pane windows)Roof (Mar–Jul 2004)
To further increase thermal resistance, we decided to replace the roof and upgrade our attic insulation. In March, we removed the 4-kW solar array as well as the existing, substandard roof tiles. The following month, we brought the attic insulation up to an R30 level. Then, in June, we installed aluminized solar sheathing on the roof. This is a thermal reflective plywood that keeps external heat out and reflects interior heat back in. We also installed roof jacks (to hold up the solar array) and then a new composite shingle roof. Finally, in July, we put in a whole-house cooling fan and whole-house heat-recirculating system (as well as two skylights, one seen in the center of the roof). The fan cools the attic and ceilings when outside temperatures are high, while the heat fan shuttles warm air from the attic to the ground floor when outside temperatures are low. Cost: $300 (attic insulation), $23 per 4' x 8' board (solar sheathing), $4,000 (new roof), $600 (whole-house fan), $570 (whole-house heater), $1,450 (two skylights)
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