Photo © Dreamstime
An attached garage is a great convenience for homeowners, but it can also be the source of indoor air quality problems in the house. Pest infestations can cause indoor air quality problems and even lead to health symptoms. A recent study1 drew a correlation between elevated indoor levels of allergens from mouse urine and exacerbated asthma symptoms. Garages are prime areas for pest entry, because overhead garage doors don't always fit tightly at the bottom or the sides. There may also be another opening to the exterior (such as decayed trim at the door casing). Mice and shrews can enter the garage through these openings and eventually find their way into the ceiling and wall cavities of the house. Exposed fiberglass insulation is a favorite nesting place for rodents and its paper facing can help a fire spread. Fiberglass insulations should never be left exposed in a garage.
I often find mold growth on the back of overhead garage doors because these surfaces are cold, resulting in condensation from high humidity. People often use a garage for storage and items that are leaning up against the cool walls, and boxes sitting on the concrete floor, can become covered with mold. I also sometimes see an extra refrigerator in an attached garage, and the gaskets, as well as the sides, can be covered with mold. In snowy conditions, people drive a car into a garage with the wheel wells covered with snow. When the snow melts and the moisture evaporates, the relative humidity of the garage air increases, which can result in mold growth on cooler surfaces.
Paints, varnishes and pesticides stored in a garage can be sources of VOCs (volatile organic compounds). Gasoline-powered equipment can leak and a gasoline-powered mower or snow blower, if started in a garage, can produce combustion products, including surprisingly high concentrations of carbon monoxide. It's important to warn your client not to leave any gasoline engine running inside the garage. This also holds true even if the garage is detached ,when there is a living space such as a guest room above the garage. Inspecting attached garages
If you are inspecting a property with an attached garage, here is some additional advice you could offer your client, depending on what you see:
• Store paints, varnishes and pesticides (including fertilizers, which often contain pesticides) in a separate building such as a garden shed. If this is not possible, be sure the lids are tightly sealed, or store these materials in metal containers with tightly fitting covers.
• Don't keep leaking gasoline-fired equipment in the garage. This might include a car in poor repair.
• If there is a furnace in the garage, make sure the duct system is airtight.
• There never should be a supply or return register in an attached garage. This presents a life-threatening condition. If there is a warm-air supply in the garage, air from the garage can be sucked into the system by convection when the blower is off. If a register is present in a garage, it should be sealed and an alternative heat source used for the space, if necessary.
• Seal up any holes or gaps around pipes, electric cables, etc. that could allow pests to travel from the garage into the house.
• Be sure overhead garage doors close tightly; add sweeps or gaskets as needed.
• Any garage door leading to the exterior or into the house should close tightly; again, add sweeps or gaskets as needed.
• To avoid attracting pests, don't store birdseed or pet food in a garage.
• Kick off snow from a car's wheel wells before driving the vehicle into the garage; this also will keep salt out that can cause damage to the concrete (if the property is new construction, recommend having the concrete sealed).
• If there is a mold problem in the garage, the space could be dehumidified.
• If the garage is to be used for storage, recommend that goods be placed on rolling metal shelves. Nothing biodegradable should be placed on the concrete. Keep clutter at a minimum.
• Clean the garage on a regular basis.
To protect their own health, occupants should pay attention to garage conditions because as far as the flow of air is concerned, an attached garage can be part of the house.
This article is from the May Indoor Air Investigations Newsletter, February/March 2012. Reprinted with permission of Jeffery C. May. © 2012 Jeffrey C. May. Visit www.mayindoorair.com
1. "Exposure to Mouse Allergen in U.S. Homes Associated with Asthma Symptoms," Päivi M. Salo, Renee Jaramillo, Richard D. Cohn, Stephanie J. London and Darryl C. Zeldin, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, N.C.; Constella Group, LLC, Durham, N.C.