Building Techniques and Energy Conservation
There are many competing definitions of green building, but all contain the element of reducing expensive energy use. A variety of practices are available to meet that goal. Below is a list of cost-effective construction methods that will save heating and cooling dollars and provide a comfortable and healthy home.
Exterior double wall construction. Two walls, from 2x4's, with a separation for a total wall width of 12 inches. Provides more room for insulation and greatly reduces thermal bridging (transfer of heat through the wooden studs). Use dense packed cellulose insulation. This insulation has an R-value of 3.8 per inch, so a 12-inch wall will net about R-40.- Roof framing, either with high heeled-trusses or conventional framing, should provide an insulation area of about 18 inches all the way to the exterior walls. That way no cold spots will exist near the outside walls. This cannot be achieved with conventional roof trusses. A good thick attic layer of cellulose, 16 inches or more, will net R-50 plus.
- Windows are the weak spot in our heavily insulated house. Many sophisticated glazing options are now available, as well as computer programs to determine the best option for the project. Ideally the main rooms should face south to gain warmth from the winter sun. Proper overhangs and shading will prevent overheating in the warmer months. In our climate the U factor (similar to R rating in insulation) should be .30 or less. The lower the better. Solar Heat Gain (SGHC), the amount of heat transferred should be .4 or higher. Air leakage rating .3 or less. These ratings will be listed on the window label. Fiberglass frames have the best energy savings.
- Cold air leakage is an important element to address. Put your hand over an electrical outlet on an interior wall some winter's day and you will feel a draft. All penetrations through the walls to the attic need to be sealed as well as the drywall against the top plate. This is achieved through special gaskets or caulking. Ceiling electrical outlets, particularly recessed lights, need careful detailing. Windows and exterior doors should be sealed with foam.
Homes need fresh air. Regardless of the heat source, a Heat Recovery Ventilator (HRV) will bring fresh air into the house in the winter months when the windows are closed. It has a heat exchanger so that the outside air is brought in at a comfortable temperature.
Follow these basic standards, add some exciting architectural details, and you should have a wonderful home.