Studies carried out by the U.S Environmental Protection Agency (EPA) have shown that air pollution levels can be up to 100 times higher indoors than those outdoors. With Americans spending more than 90 percent of their time indoors, the increase of indoor pollution levels is a threat to their health and indoor comfort. As more is learned about indoor pollutants and the effect they have on building occupants, indoor air quality (IAQ) has increasingly become an integral component of sustainable building design. Learning the causes of poor indoor air quality can help building and design professionals create more sustainable and healthier interior environments for building occupants.
Where poor IAQ begins
Indoor air quality first became a national problem after the energy crisis of the 1970s inspired the design of airtight buildings to prevent the leakage of conditioned interior air. Though tight construction seals off the escape of conditioned air, it also traps harmful water vapor and volatile organic compounds (VOCs) inside the structure – which are the two leading causes of poor indoor air quality.
Mold growth. Mold can form and grow on any surface that provides a food source or that is surrounded by moderate temperatures, oxygen, and sufficient moisture. The best examples of mold food sources are cellulose-based substances.
In today’s buildings, food sources for mold are readily available in the form of untreated paper-faced gypsum panels, wood wall studs, and wood-based sheathings. Once moisture is introduced to the mold food source, long-dormant mold spores can gain a foothold. As long as the food and moisture sources are supplied, the mold colonies will continue to grow and prosper.
When mold has spread throughout a building, occupants may notice unpleasant odors and experience a variety of health problems, such as headaches, breathing difficulties, skin irritation, allergic reactions, and aggravation of asthma symptoms.
Volatile organic compounds. VOCs are gases or vapors, such as formaldehyde, given off by solids and liquids. VOCs often cause short and long-term adverse health effects.
All products manufactured with organic chemicals have potential for releasing VOCs while in use. These include paints and lacquers, paint strippers, building materials, furnishings, cleaning supplies, pesticides, etc. Though many manufacturers have worked hard in recent years to reduce the volatile organic compounds emissions of their products to very low levels.
To keep VOCs levels at a minimum, it is important for building maintenance staff to use only low-VOC cleaning supplies, pesticides, and air fresheners. On the other hand, building and design professionals should also specify low-VOC finishes and building products.
It’s important to check individual product data to be certain. GREENGUARD® certification from UL Environment is one resource for determining if a product’s VOC levels are within acceptable limits.
Improving IAQ through moisture management in wall assemblies
Fortunately, poor indoor air quality and the health problems that come with it are avoidable. Adequately ventilated buildings with an effective moisture management strategy in the wall assembly can help eradicate various interior air pollutants.
Here are some guidelines on the contents of a steel stud cavity assembly:
- First, always use a water-resistive barrier (WRB) — it’s the first line of defense against rainwater intrusion. Water will enter somewhere, somehow, so use a ventilation and drainage space between the masonry façade and the WRB.
- It is important to maximize condensation control — first, by using insulating sheathings. Use exterior air or wind barriers, since air can transport considerable moisture into assemblies if not blocked. Use interior air barriers to help prevent wintertime moisture from migrating and condensing on cold surfaces.
- Next, use adequate products — such as fiberglass insulation, smart vapor retarders, and moisture and mold-resistant gypsum panels — to control the wintertime moisture and allow assemblies to dry during other seasons.
Three solutions to control moisture in commercial wall building assembly
- Fiberglass Insulation
When exposed to moisture, fiberglass insulation neither absorbs nor holds water. It is also resistant to mold and microbial growth, making it an excellent insulation choice in moisture-managing wall assembly designs. Learn more about InsulPure™, the evolution of our insulation solutions.
- Smart Vapor Retarders
Originally developed, tested, and commercialized in Europe, smart vapor retarders resemble polyethylene film, but are actually polyamide, a nylon-based material. Polyamide film retards moisture under dry conditions, but if relative humidity in the wall cavity increases above 60 percent, they dramatically open up to a much higher permeance — which allows drying toward the interior of the building.
In summer, when the air is humid, the moisture penetrates through the pores into the building interior, allowing building materials to dry out. If the relative humidity decreases, the pores close up again, and the membrane then acts as a retarder to moisture. In the winter, this vapor retarder protects the building materials behind the membrane from condensation.
Field tests have proven that smart vapor retarders like CertainTeed’s MemBrain™ Continuous Air Barrier & Smart Vapor Retarder effectively reduce the risk of moisture damage in the building envelope by increasing the construction’s tolerance to moisture load.
- Moisture- and Mold-Resistant Gypsum Panels
In areas of the building that are moisture-prone, it is a good idea to install mold and moisture-resistant treated gypsum panels instead of standard paper-faced gypsum panels. Traditional gypsum panels are paper-faced and therefore a potential mold food source under moisture-heavy conditions.
Since there is no limit to where mold spores can travel, it is wise to specify mold and moisture-resistant -resistant gypsum panels in all high-humidity climates and for any areas of a building that will likely have high moisture levels, including kitchens, showers, washrooms, locker rooms, basements, laboratories, laundry rooms, and any area that will occasionally be exposed to splashes of water.
Today, gypsum panel manufacturers offer many enhanced versions of non-fire rated and fire-rated Type X gypsum panels with enhanced mold and moisture resistance. Most common are paper-faced gypsum panels treated with bio inhibitors, such as CertainTeed M2Tech®, which prevent the growth of mold whenever moisture is introduced to the facing. Some manufacturers also now offer paperless gypsum panels, with fiberglass mats in place of paper facings. CertainTeed GlasRoc® gypsum panels utilize the aforementioned fiberglass mats in place of paper facings. Additionally, CertainTeed M2Tech and GlasRoc gypsum panels achieve the best possible score of 10, for mold resistance, per ASTM D3273 Standard Test Method for Resistance to Growth of Mold on the Surface of Interior Coatings in an Environmental Chamber.
Indoor air pollution caused by volatile organic compounds and mold growth is a significant threat to the health of building occupants and an obstacle standing in the way of sustainability in a building.
Following the guidelines above will help to create a drier, mold-free interior environment, which in turn will result in higher quality interior air. If maintained, high indoor air quality creates a healthy and comfortable interior environment that will last for many years.
Consult with CertainTeed credentials contractors for pro tips on how to improve the indoor air quality of new construction buildings or existing facilities.
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