PATH - A Public Private Partnership for Advancing Housing Technology
Implementing the Indoor Air Quality Tech Set
There are no defined federal regulations to benchmark indoor air quality, however, IAQ may be rated by standards and guidelines recommended by industry experts in health, government, and research. Generally, acceptable indoor air quality is defined as measurements under maximum thresholds for these indicators -- carbon dioxide, formaldehyde, humidity, mold, radon, particulate matter, and volatile organic compounds (VOCs) -- as sampled within a home. VOCs are any number of compounds that contain carbon and different portions of other elements such as hydrogen, oxygen, fluorine, chlorine, bromine, sulfur, or nitrogen that evaporate easily at room temperature and often have a sharp smell.
Signs that indicate a possible IAQ problem in existing homes are moisture condensation on the interior of windows, musty odors or stuffy air, dirty register and return air grills, mildew or mold, or occupant discomfort.
1. Air Quality Testing
Testing for many pollutants can be expensive, so source control is the preferred strategy, particularly in new construction. However, radon, an undetectable gas that can cause lung cancer at high exposures, is an exception to these high cost tests. Radon test kits can be purchased for as little as $9.95, placed by the builder or occupant to collect a sample under a controlled set of testing criteria, and returned to a lab for analysis. Where radon is detected or is likely to be present there are simple, reliable construction techniques that make contamination inside a home relatively easy to control.
2. Eliminate VOCs, Formaldehyde, and Other Contaminants
Many of the other named contaminants are detectable by occupants as odors or eye, nose, and throat irritants. To control the source of other air contaminants eliminate them by specifying materials (both permanent and decorative) that do not contain VOCs and/or formaldehyde. Laminated wood products like sheathing, cabinet parts, and flooring are common sources of formaldehyde. Seal the surfaces with low VOC finishes or specify products that have eliminated these from the manufacturing process. For this process to be maximally effective, occupants must use the same diligence in selecting furnishings, carpet, draperies, cleaners, etc.
Refer to Section 6. of EPA's ENERGY STAR Indoor Air Package Pilot Specifications for specific low VOC building materials and preparation and installation guides.
3. HVAC System Designed by a Professional
Surveys have indicated that occupants’ perception of good indoor air quality is highly related to thermal comfort, so HVAC systems should be properly sized. System best practices are enumerated in PATH's Tech Set #3, HVAC: Forced Air System. Specification references for sizing and installing HVAC systems while controlling ventilation, air infiltration and leakage is contained in Section 4 of EPA's ENERGY STAR Indoor Air Package Pilot Specifications.
Humidity control prevents the indoor growth of mold, mildew, viruses, and dust mites. Maintenance of an annual relative humidity range between 30-50 percent will control the source of many of these known biological contaminants. Winter humidification and summer dehumidification controls/modules can supplement central HVAC systems when climate excesses require additional conditioning measures.
Spot ventilation is a method of expelling moisture and odors that are regularly generated within a home. See the U.S. Department of Energy's fact sheet on spot ventilation strategies.Fans in bathrooms and over gas-fired kitchen grills are examples of spot ventilators. When switched "on," fans remove the potential pollutant source while introducing fresh air by drawing it into the home through leaky areas of the building. This approach slightly depressurizes the house in the process of venting so it is sometimes referred to as an unbalanced ventilation method.
Unbalanced methods may provide adequate IAQ control for homes of many styles in many climates. Low sone (very quiet) fans are more likely to be used by an occupant. In-line fans can service several locations with seemingly- silent operation and greater energy efficiency. Fans can be wired to timers that provide a calculated level of air exchange.
Whole-house ventilators are integrated with the HVAC system to provide a measured amount of outdoor air to the inside unit for conditioning at regular intervals. Available systems range from a simple dampered air duct supplying outdoor air to an air handler to large intake/output units housing heat exchangers. These systems do not rely on air leaks in the home to deliver outdoor air. High-efficiency air filters
High-efficiency whole-house air filters can also be installed in central forced air HVAC systems to provide filtration for the entire house. High-efficiency air filters greatly reduce the number of airborne particles when compared to the standard 1-inch thick filter installed on most central HVAC systems.
All HVAC systems contain some method for filtration of the room air that is returned to the unit for re-conditioning. Filters vary by the size of particulates that can be trapped, ability to filter out moisture, and ability to sterilize micro-organisms (usually with ultra-violet light). Some filtration methods can be implemented by switching out the filter medium whereas others require an additional unit. Stand-alone room units can accomplish some spot filtration, as well.
4. Durable Building Envelopes
A well built home repels moisture and air with good design features like covered entries, redundant barriers and grading that moves water away from the structure. Follow the steps outlined in PATH's Tech Set #2, Durable Building Envelope, to eliminate moisture intrusion.
Air sealing the perimeter of a structure can make a significant difference in improving air quality inside the home.
In some cases such as homes with attached garages, it is particularly important to ensure the boundary between living and non-living areas is sealed properly. This will keep pollutants from seeping into the living areas. One study found that 75 percent of the benzene in the home environment is introduced from the garage.
5. Provide Sealed Combustion Appliances
Heating equipment that burns natural gas, oil, or any other fuel that relies on an open flame within the home, should be vented to the outside by a sealed vent so that burning byproducts cannot backdraft into the home. Backdrafting is the movement of unwanted byproducts from burning like smoke, ash, and gases down the vent stack or through the appliance into the house. Backdrafting results from internal depressurization that can be caused by wind currents or unbalanced ventilation.
In addition to depositing chemical toxins like carbon monoxide in the home, backdrafting is a source for particulate matter (PM) - the term for particles found in the air that include dust, dirt, soot, smoke, and liquid droplets. PM can be inhaled and trapped in the respiratory system causing congestion and breathing difficulty.
Specification references for selecting and installing properly sealed combustion appliances are contained in Section 5. of EPA's ENERGY STAR Indoor Air Package Pilot Specifications.
6. Occupant Vigilance
The occupants of the home ultimately control the quality of indoor air long after good material specification and construction practices were employed in its construction. Particulate control starts with keeping outdoor contaminants out -- practices like regular (out-of-home) washing and brushing of pets, insect and pest control, and wiping or removing shoes worn outdoors upon entering a home go far toward PM curtailment. Regular particulate removal via dusting, damp mopping and vacuuming is required to maintain a healthy indoor environment.
Without due care, occupants may introduce chemical contaminants with their selection of cleaning products, furnishings, and finishes. HVAC system maintenance and filter replacement should be performed at regular intervals. Smoking, using aerosol sprays and room fresheners, and candle burning should not be done inside.
Content updated on 9/25/2007
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