Sick Building Syndrome FAQ

Sick Building Syndrome –sometimes called Building-Related Illness—is typically caused by indoor air pollution. This problem has become more acute because we spend more time indoors than in generations past, and because buildings tend to be more airtight, allowing air pollutants to become more concentrated. Inadequate or improper ventilation is often a factor in SBS, but many other factors can also be involved.

Fortunately, many manufacturers of paints, finishes, furnishings, and cleaning products now produce only no or low-VOC versions of their products. Pay attention to VOC labeling information when shopping and you shouldn’t have to worry about this IAQ factor.

Your crawl space IS connected to your living space, through hundreds of gaps and cracks around ductwork, plumbing pipes, electrical lines, and building materials. Research has shown that as much as 40% of the air you breathe can come from the basement or crawl space. Microscopic mold spores are transported on crawl space air that moves up into your living space by natural convection –a phenomenon that building scientists call the Stack Effect. Instead of hoping that mold in the crawl space won’t affect IAQ (it will!), it’s better to eliminate this mold source through crawl space encapsulation, dehumidification, and mold eradication.

Leaky ductwork in a basement, crawl space, or attic can suck dusty air from these areas into the air circulated through the living area by your forced-air HVAC system. Having your ductwork professionally sealed will cut off this dust supply. It’s also smart to air-seal your attic and basement to stop the air movement that takes place because of the Stack Effect. The warm air that moves up and out of your living space through attic leaks will draw an equal volume of outside air into your basement, creating upward air pressure that can carry dust from the basement to the living areas.

Unfortunately, some HVAC contractors still make it common practice to install oversize air conditioning systems that end up cooling too quickly –before the system can adequately dry out the air. When the thermostat calls for cooling, a high volume of cold air blasts into your living space, lowering the temperature so quickly that the thermostat cuts power to the AC unit after just a short time. A longer run time is required to remove more moisture from the air, but an oversized system doesn’t provide this opportunity. More modern AC systems feature variable speed and feedback circuitry that moderates performance to optimize both cooling and dehumidification.

Basements and crawl spaces are naturally moist environments, even when their floors stay dry. Soil moisture is absorbed by the masonry walls and floor and released into the space. There are several improvements you can make to turn a mold-friendly environment into a mold-hostile environment. Air-seal the basement so that moist outside air won’t infiltrate through cracks and gaps around perimeter walls. Insulate basement walls with rigid foam to reduce the number of cool interior surfaces where condensation can occur. Install a basement dehumidifier to dry out the air, because mold has difficulty living below 60% humidity. Finally, limit the use of organic materials (paper-faced drywall, plywood floor sheathing, wood paneling, etc.) that will provide ideal mold habitats if they become damp.

This is a common problem in many houses, and it’s most likely to occur during cold weather. Heated air from your living space leaks into the attic. When the warm air comes into contact with a cold surface (the roof sheathing), condensation occurs. Because this happens continually during the heating season, sections of roof sheathing stay wet for a long period, creating ideal conditions for mold to take hold. Attic mold problems worsen considerably if a clothes dryer or bathroom vent fan dumps moist air into the attic space. The solution to both these mold problems is to thoroughly air-seal the attic and to duct dryers and vent fans to the exterior instead of to the attic.