Design Options

Advanced wall framing techniques can be used that will reduce the energy losses through the walls with little or no additional costs.

Some new homes are built using metal frames instead of wood. Such frames are not susceptible to insect problems that can damage wood-framed structures.However, when you insulate a metal-framed building, it is important to recognize that much more heat flows through metal studs and joists than through pieces of wood. Because of this difference, placing insulation just between the wall studs, or just between attic or floor joists, doesn't work as well for metal-framed houses as it does for wood-framed houses.

Insulating concrete forms can be used to construct walls for new homes. These special concrete walls come in a variety of configurations and can provide additional thermal mass to your home to help reduce the effect of outdoor temperature swings.

The most common house type in this country is the light-construction frame house. Massive walls are less common, and include buildings made from concrete, concrete block, and log. These buildings will use less energy than wood-frame construction in many parts of the country because they can store heat from the daytime sun to provide needed heat at night, or can cool down at night to reduce air-conditioning loads during the day.

Structural insulated panels can be used to construct a house. These panels sandwich plastic foam insulation between two layers of a wood or composite product, thus eliminating the need for structural wood framing members. These systems save energy in two ways, first by reducing the heat losses that would have gone through the wood frame, and second by reducing air leaks. Both of these changes represent significant energy savings. Just stopping the energy flowing through the wall framing could save 25% of the wall's energy losses.

Attic Ventilation is important that the house design, and construction, minimize the transfer of moisture from the living space to the attic. To handle any moisture that does migrate into the attic, traditional attic design calls for ventilation. Attics may be ventilated with a combination of soffit vents at eaves and continuous ridge vents. Attic vents may also be installed in gable faces. Many codes and standards require one square foot of unobstructed ventilation opening for each 300 square feet of attic floor area if a vapor retarder is included in the ceiling separating the attic from the living space.

During the house design phase, you can choose a cathedralized attic, which is not ventilated, unless attic ventilation is required by code in your area.

One advantage of this approach is that the attic will retain any energy lost by ductwork in the attic. Up to 25% of your heating and cooling energy can be wasted by leaky ductwork in a traditional attic.

A disadvantage of an unventilated attic is that the underside of the roof has a greater area than the attic floor. This greater area, and the downward-facing geometry, cause this option to be more costly than insulating the attic floor, so that usually the installed insulation R-value is less. The lower R-value and the greater area mean that more heat is lost through the cathedralized attic roof than would have been lost through the traditional attic floor. Also, a ventilated attic can reduce summer air-conditioning loads relative to the cathedralized attic. The home owner must balance these two effects, reduced duct energy losses versus increased heating and cooling loads. Of course another option is to ventilate the attic, but locate the ductwork elsewhere within the conditioned part of the house, such as between floors in a multi-story building.