Designing and building an energy-efficient home that meets the many considerations faced by home builders can be challenging. Some approach the challenge by using alternative building materials like those used in straw bale construction. However, any house style can be constructed with materials and building techniques that will require minimal amounts of energy to heat and cool, and still be comfortable, healthy, and affordable. It's easier now to get your architect and builder to use improved designs and construction methods. Even though there are many different design options available, they all have several things in common: a high R-value, tightly sealed thermal envelope; controlled ventilation; and lower than usual heating and cooling bills.

Some designs are more expensive to build than others, but none of them need to be extremely expensive to construct. Recent technological improvements in building elements and construction techniques, and heating, ventilation, and cooling systems, allow most modern energy saving ideas to be seamlessly integrated into any type of house design without sacrificing comfort, health, or aesthetics. The following is a discussion of the major elements of energy-efficient home design and construction systems. The EREC has other, more specific information on these topics available.

The Thermal Envelope

A "thermal envelope" is everything about the house that serves to shield the living space from the outdoors. It includes:

• Air and Vapor Barriers
• Air Seals
• Controlled Ventilation
• Foundations and Slabs
• Insulation
• Wall and Roof Assemblies
• Windows

The design and material choices made for each of these areas, plus the quality of the construction work, will determine the home's overall efficiency.

Heating and Cooling Requirements

Houses incorporating the above elements should require relatively small heating systems (typically less than 50,000 Btu/hour even for very cold climates). Some have nothing more than sunshine as the primary source of heat energy. Common choices for auxiliary heating include radiant in-floor heating from a standard gas-fired water heater, a small boiler, furnace, or electric heat pump. Also, any common appliance that gives off "waste" heat can contribute significantly to the heating requirements for such houses. Masonry, pellet, or wood stoves are also options, but they must be operated carefully to avoid "back drafting."

If an air conditioner is required, a small (6,000 Btu/ hour) unit can be sufficient. Some designs, like the ACT2 houses in arid Davis, CA use only a large fan and the cooler evening air to cool down the house. In the morning the house is closed up and it stays comfortable until the next evening.