Workplace indoor air quality (IAQ) concerns were brought to the forefront in 1994 when the Occupational Safety and Health Administration (OSHA) issued its first proposal for regulating IAQ. Since then, improving IAQ in schools, healthcare facilities, and commercial buildings has become a high priority of the Green building movement. Now, the best step building and design professionals can take to improve indoor air quality is to be proactive and use building science principles.
Common Causes of Poor IAQ
Indoor air quality can be threatened by a variety of things within a building such as moisture, mold spores, and dust mites, as well as volatile organic compounds (VOC) and poorly designed air distribution systems.
Moisture and Mold
Moisture, or humidity, presents a big problem in airtight buildings lacking proper ventilation. Mold can form on many surfaces within wall, floor, and ceiling assemblies, eventually creating breathable airborne particles that are unhealthy for building occupants. Moisture can also get trapped inside wall cavities, saturating insulation and building materials. Wet insulation loses R-Value, making the building less energy efficient; it can also foster mold growth.
Volatile organic compounds are carbon-based organic compounds that often come from solvents, cleaners, and the exhaust given off by mechanical and electrical equipment, as well as building materials and furnishings. In most airtight buildings, there is not adequate ventilation to allow appliances to exhaust freely, causing them to backdraft harmful combustion products, such as carbon monoxide, into the building’s interior. This stresses the importance of a good heating, ventilation, and air-conditioning (HVAC) system to rid the building of these pollutants.
A poorly designed HVAC system can lead to more energy use and higher utility costs, not to mention discomfort for building occupants and other ventilation problems. Ducts tend to produce moisture during air transmission. Without insulation and periodical maintenance, this can develop into a serious IAQ threat. In the summer, condensation often forms on uninsulated ducts when cool air passes through warm ductwork. (The same is true in winter, when warm air passes through cold ducts.) Although this is a natural occurrence, it can create a breeding ground for harmful mold if dust or dirt mixes with condensation. This is a major concern, as ductwork is the vessel by which conditioned air is distributed throughout the building. Properly insulated ductwork and a periodical duct cleaning schedule provide an excellent defense against this substantial contributor to poor building IAQ and respiratory ailments.
Solutions for Poor IAQ in Your Facility
There are plenty of ways to minimize the sources of poor IAQ in your facility. Much can be achieved with good moisture management and HVAC duct design.
- It is extremely important to make sure the wall cavities and other unoccupied spaces of the building are properly equipped with quality insulation assemblies that include a breathable vapor retarder. This will not only increase the thermal performance of the building, but it will also minimize excess moisture. With the help of a vapor retarder facing, such as CertainTeed MemBrain™, InsulPure™ fiberglass insulation is a powerful weapon against moisture and the damage it causes in homes and buildings.
- A standard vapor retarder’s job is to resist the movement of water vapor to cold surfaces. A breathable vapor retarder, though, will change its permeability with the fluctuation of humidity levels from season to season. This “smart” facing helps reduce cavity condensation during winter and promotes interior drying during more humid seasons. Smart vapor retarders are available either separately or pre-attached to fiberglass batt and roll insulation. It is also recommended to seal off all penetrations in the building and install effective air barriers.
Ventilate It Right
- An efficient HVAC system is vital for a good IAQ. First off, choose energy-efficient HVAC equipment. Seal ductwork with appropriate mastic adhesive or tape to prevent leakage and, wherever possible, locate ductwork in a conditioned or semi-conditioned space. This will minimize leakage to and from the outside environment, and prevent pressure imbalances. This can also be achieved by using ducted returns instead of wall or floor chases.
- Design HVAC systems for proper exhaust ventilation and moisture removal, so that more moisture and pollutants are extracted from the air. Of course, a more humid climate will require a system that will adequately handle more moisture.
- Another must for optimum leak-free performance and moisture management: Opt for either sheet metal ducts insulated with quality fiberglass liner and duct wrap or ducts fabricated from fiberglass duct board, all with enhanced surfaces. For example, CertainTeed ToughGard® fiberglass duct insulation products are GREENGUARD® certified for very low indoor pollutant emissions, which helps create superior indoor air quality performance.
Once installed, the best way to ensure ducts stay mold-free and perform efficiently is through a regular maintenance schedule. This is vital, regardless of whether the ductwork is internally insulated or uses bare sheet metal. Since preventative maintenance is very important in HVAC system operation, many architects and engineers have begun to add this recommendation to their specifications.
Designing a building that’s merely airtight is not the answer to sustainability. The answer is designing a properly insulated building with adequate ventilation. Following these guidelines should provide a solid start toward fostering good indoor air quality for healthier buildings and happier occupants.
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