Ensuring healthy indoor air quality in a home starts with the very foundation. Many simple building techniques, from radon-resistant construction to drainage planes, can prevent unwanted air-quality problems in the future. To prevent unwanted moisture and contaminants from entering, it is very important to build a tight home, but it is also crucial to provide ventilation to the home to facilitate fresh-air exchange. Once the home has been constructed as healthily and durably as possible, consider the interior finishes and the chemicals used in glues, paints and stains. Below is a checklist of items to help ensure healthier indoor air. For more information, review the Energy Star Indoor Air Package requirements at http://www.EnergyStar.gov.

Moisture Management
• Install a continuous drainage plane behind the exterior cladding.
• Install a capillary break between foundation and framing.
• Fully and properly flash windows, doors and roofing.
• Install a surface-water management system. Final grade should be at least a half-inch per foot sloped away from the house. Gutters must be present and functional, and must drain onto a finished grade at a minimum of five feet from the building foundation.
• Crawl-space flooring should have 100-percent coverage with a sealed vapor barrier. Consider a sealed, nonvented crawl space for added durability.

Ventilation
The home needs to be as tight as possible through proper air sealing. Then, fresh-air ventilation needs be provided mechanically to the home (not too much, not too little). The American Society of Heating, Refrigerating and Air Conditioning Engineers requires 7.5 cubic feet of air per minute per person (i.e., per bedroom) plus 7.5 cfm, plus an additional 1 percent of total floor area of fresh-air ventilation.

This isn’t as complicated as it sounds. The two most common methods for achieving this are: 1) Run a supply duct from a clean source outside of the home into the return duct of the HVAC system. Then install a controller that will make sure your home gets plenty of fresh air even when the air handler is not running often. 2) Install a balanced system. Commonly known as Heat Recovery Ventilators or Energy Recovery Ventilators, these high-tech systems bring in fresh air while exhausting stale air to the outside. Heat (and moisture, in the case of the ERV) is transferred in the process, making it the most energy-efficient ventilation option.

• Install a properly sized and sealed HVAC unit (see “HVAC” checklist). The home needs to maintain less than 60 percent relative humidity.
• All ventilation exhaust fans (bathrooms, range hoods and clothes dryers) need to be vented outdoors. Kitchen-range hoods should not exhaust more than 350 cfm. Bath fans should exhaust at least 50 cfm, so installing a 75- or 90-cfm bath fan is recommended to make up for duct length. Consider installing low-sone fans on a timer or a humidistat. 
• Install Minimum Efficiency Report Value 8 or higher HVAC filters, but make sure the equipment is designed be to accommodate pressure drop from the filter. 
• Protect ducts from dirt and debris until construction is completed.

Combustion Safety
• Combustion equipment, such as gas furnaces and water heaters, must either be sealed combustion, power-vented or installed outside the conditioned spaces. Do not install unvented fireplaces.
• Install one hardwired carbon-monoxide detector per 1,000 square feet of living space (minimum one per floor) in all houses where there is an attached garage or where any combustion appliance is used in the structure.
• Common walls to the garage need to be properly air-sealed, and doors to garages need to be weather-stripped.

Radon and Pest Resistance
• Install a radon-mitigation system that depressurizes the slab, and properly air seal any penetrations from the foundation to the home.
• Perform a radon test before moving in. For more information, visit http://www.epa.gov/radon.
• Consider nontoxic borate treatment or bait/monitoring systems for termite control.
• Install termite flashings that provide a physical barrier between the foundation and the wood structure.

Materials
• Use formaldehyde-free insulation and building materials wherever possible.
• Use low-VOC (volatile organic compound) paints.
• Use low-VOC stains and finishes on all wood work.
• Use solvent-free adhesives and glues.
• Don’t install carpet. If you do, use a low-VOC carpet rated by the Carpet and Rug Institute.

Sources for this fact sheet include Advanced Energy System Vision Guidelines, Southface Energy Institute Technical Bulletins, HealthyBuilt Homes program guidelines and Energy Star guidelines for homes and indoor quality.