Checklist: Indoor air qualityBy Maggie Leslie on 03/22/2010
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 an indoor air quality checklist.
• A continuous drainage plane is installed behind the exterior cladding.
• A capillary break is installed between foundation and framing.
• Windows, doors and roofing are fully and properly flashed.
• A surface-water management system is installed. Final grade is at least a half-inch per foot sloped away from the house. Gutters are present and functional, and they drain onto a finished grade at a minimum of five feet from the building foundation.
• Crawlspace flooring has 100 percent coverage with a sealed vapor barrier. Consider a sealed, nonvented crawlspace for added durability.
• The home is as tight as possible through proper air sealing.
• Fresh-air ventilation is provided mechanically to the home. 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.
• A properly sized and sealed HVAC unit is installed (see HVAC checklist). The home needs to maintain less than 60 percent relative humidity.
• All ventilation exhaust fans (bathrooms, range hoods and clothes dryers) are vented outdoors. Kitchen-range hoods do not exhaust more than 350 cfm. Bath fans 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.
• Minimum Efficiency Report Value (MERV) 8 or higher HVAC filters are installed and the equipment is designed to accommodate pressure-drop from the filter.
• Ducts are protected from dirt and debris until construction is completed.
• Combustion equipment, such as gas furnaces and water heaters, is either sealed combustion, power-vented or installed outside the conditioned spaces. There are no unvented fireplaces installed.
• One hardwired carbon-monoxide detector is installed 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 are properly air-sealed, and doors to garages are weather-stripped.
Radon and Pest Resistance
• A radon-mitigation system is installed to depressurize the slab. All penetrations are properly air sealed from the foundation to the home.
• A radon test was performed before moving in. For more information, visit http://www.epa.gov/radon.
• Termite flashings that provide a physical barrier between the foundation and the wood structure are installed.
• Consider nontoxic borate treatment or bait/monitoring systems for termite control.
• Formaldehyde-free building materials are used wherever possible.
• Low-VOC (Volatile Organic Compound) paints are used.
• Low-VOC stains and finishes are used on all wood work.
• Solvent-free adhesives and glues are used.
• No carpet is installed. If carpet is installed, a low-VOC carpet rated by the Carpet and Rug Institute is used.
For more information, review the ENERGY STAR Indoor Air Plus requirements at http://www.EnergyStar.gov.
Sources for this checklist include Advanced Energy System Vision Guidelines, Southface Energy Institute Technical Bulletins, HealthyBuilt Homes program guidelines and Energy Star guidelines for homes and indoor quality.
[Maggie Leslie is program director of the WNC Green Building Council. She can be reached at or at (828) 254-1995.]