Last week the United States House of Representatives passed the HomeStar bill which authorizes $5.7 billion over two years for energy efficient upgrades to homes. The bill will now be reviewed by the Senate. The bill has two parts: The Silver Star program provides up-front rebates of up to $3,000 for specific energy-efficient improvements in home such as energy efficient appliances, duct sealing, insulation, or new windows or doors. The Gold Star programs provides up to $8,000 to people who conduct an energy audit and implement steps to cut energy use in their homes by more than 20 percent.
But one of the biggest changes within the HomeStar program is the recognition of the contribution of insulated siding to the energy efficiency of buildings. When we talk about the weatherization programs we are talking about adding insulation to existing buildings. The most difficult place to add insulation is on the side walls. Insulation is, traditionally, between the framing cavity between the studs – between the sheathing and interior drywall. Sometimes it isn’t even possible to add insulation to these cavities post construction. Also, it doesn’t account for framing. This is the big issue encountered even with new construction, getting the whole wall insulation value as high as possible to improve the all over performance of the system – the studs, the cavities, the framing, and the floor lines. When insulation is added between two studs, on the best given day, it only insulates 75 percent of the wall because framing accounts for 25 percent of the wall.
When insulated siding is used on a building it not only increases the insulation value it covers up the framing on the outside which cuts down on the thermal bypasses and improves the overall whole wall R value which is very difficult to do.
Hats off to the Home Star program and the Federal government for recognizing the significant contribution that insulated sidings can make towards the overall performance of the building.
Lucas Hamilton is Manager, Building Science Applications at CertainTeed Corporation