Every month, we seek to bring our readers insight from the worlds of home construction, home repair, and home maintenance straight from local Northwest Washington contractors in a segment we call “3 Questions.” Yep, you guessed it: we ask three questions, and the contractors answer them.
This month, we talk about mold in the attic with Bob Shupe, Principal at Cleaner Guys in Mount Vernon.
Q1: Mold: It’s a hot topic and frequently discovered in attics above homes in the Pacific Northwest. Is this a health issue for the home’s occupants?
Unfortunately, the answer has to be “maybe.” There are numerous variables involved with making a determination like that where the occupants of a home are concerned. Generally, mold in an attic space is not an immediate health concern/risk for the occupants simply due to the unlikely exposure to attic mold. People spend little or likely no time in their attic so they would not be directly exposed to it. Additionally, most health risks associated with mold are chronic exposure issues, not acute exposure. An example of chronic exposure would be to have a bedroom in a basement where there is groundwater intrusion regularly causing active mold growth in a wall cavity. Because people spend many hours per day in their bedroom, an active mold problem in the walls could develop into a health problem. There are still many factors that contribute to this (including the general health of the person exposed, the severity of the mold problem, general home cleanliness, etc.). Significant risk multipliers would be pre-existing health issues such as respiratory or immune system conditions/disease etc.
For the structure itself, it is crucial to keep in mind that active mold colonization is slowly consuming the building materials. As a microorganism, mold is using the wood of a building as a food source. Eventually, serious structural damage may be done if mold is not removed/remediated/killed, etc. There also has to be water for the mold to be actively growing. Often times, the water intrusion and/or water damage can be a bigger problem in terms of damage, health concerns and cost than the mold. If a house has a bad roof and water is leaking in—causing damage to sheeting and framing materials—the roof is eventually going to cave in, causing potential harm to the occupants regardless of their pre-existing medical conditions. We have all seen the abandoned home or old barn where the roof eventually caves in. This is the same thing, and there is almost always going to be a mold component to the structural collapse in the case of water intrusion. This is a long/slow process and not likely to happen in an occupied home, but the illustration is realistic. Keep in mind that house framing/roofing systems are engineered for a particular load rating. As the materials deteriorate so does the load rating. This does not mean the roof is going to fall in under its own weight, but it could mean that the roof will not hold a snow load as it should or resist wind forces or perhaps a tree falling on the roof. A weakened roof structure would likely lead to a worse failure of the systems that would normally be expected because the roof and framing strength have been compromised by water damage and/or mold growth. These are pretty extreme examples though, most mold growth we observe in homes is due to poor or non-existent ventilation or other water vapor issues than significant water intrusion. The result is slow, mild mold/mildew growth on sheeting materials that is frequently seasonal and going through phases of growth and dormancy. Most molds thrive in narrow bands of temperature and moisture content levels. In the Pacific Northwest, we have sufficient seasonal changes where you might get mold growth in the fall when we have rain and moderate temperatures and then slowing of growth during the earlier part of the year when it’s cold, followed by a re-emergence of growth in the spring and then dormancy in the summer when it’s hot.
Back to the potential of specific health issues for people living in a home with active mold growth in an attic, the natural air flow in a building is working in favor of the occupants. Warm air rises and—for the most part—air coming into a house goes up, through and out of the attic. There are anomalies of course, but as a general principle, mold or spores are unlikely to migrate from roof sheeting to the living space of a home. If there is water intrusion to the degree that the ceiling drywall is getting wet and mold is growing on the drywall, I would eventually anticipate mold growth on the drywall in the living space—which becomes a very different issue than mold in an attic.
Q2: In your experience, what’s the most frequent cause of mold growth in attics?
All attic mold is caused by the same thing: the right growing conditions for mold. The key ingredient for mold growth is water. It is the key because, realistically, it is the only ingredient we can have a positive impact on. Like any plant, mold needs water, air, food and a temperature range appropriate for the species of mold. We build houses out of wood (food source), and the air is obviously present. Therefore, by controlling water issues, we can control mold growth. This means proper ventilation, no acute moisture sources such as leaks, bathroom vents blowing steam into the attic space, etc. Engineering controls can be put in place to give an attic better resistance to higher levels of water and water vapor—but it’s always best to prevent water from entering initially. Building materials can be treated with mold-resistant coatings, powered fans can be installed to create high air flow rates—but if you have a bathroom fan blowing steam in the attic every time someone takes a shower, just fix that. If there is some mold as a result, it can be remediated. Once this occurs, this will likely be the end of it because both the cause and effect have been corrected. Sometimes, however, the cause cannot be adequately repaired, and so some degree of a long-term solution needs to be implemented. For example, if the home is in an area where it’s shady most of the time, it’s more likely there will be moisture buildup/condensation in the attic than a home where the roof is in the sun most of the time. This is the same reason we see moss growing on one side of a tree and not the other. In a situation like that, applying a mold-resistant sealer and a powered exhaust fan that is controlled by a humidistat (turns the fan on/off based on the humidity in the attic) can work together to help an attic avoid mold colonization even though there are higher-than-average humidity levels. Applying a mold-resistant sealer will also make it much easier to identify mold growth through routine visual inspection and—to some degree—it will be easier to remediate from a sealed wood surface than a bare/raw wood surface. If a high-quality sealer is used, there should not be mold growth on the sealer for a very long time. If mold does start growing on a sealed surface, it’s actually more likely that the mold is eating dust or other surface contamination than the wood that is sealed.
Q3: Can you give an approximate average cost for remediation of mold in attics?
There really is no magic formula for arriving at the cost of a mold remediation project, especially in an attic. To properly conduct a mold remediation project you have to have containment set up to prevent cross-contamination (workers, tools, supplies, and equipment going in and out of the contaminated area to an un-contaminated area). We do this through building temporary structures in the house that isolate the work area from the home. We use large air filtration equipment to keep the work area and containment chambers under negative air pressure (vacuum) so that air migration is always from the work area (through a HEPA filter and then to the outdoors). Access to the attic space itself and then access around the attic weigh heavily on the cost of a project. If the mold is in a garage with no drywall ceiling or insulation and the roof is framed with rafters instead of trusses, the cost will be less. If the attic access is a small hatch in the ceiling of a closet and the roof is framed with trusses, the cost is going to be higher due to the additional time required to access all of the affected areas for cleaning/remediation. In addition to investigating the underlying cause of the mold/water sources, etc., it is crucial to assess the access to provide a comprehensive bid on work before bidding on the remediation project.
BONUS: What advice can you share with our audience about preventing mold growth in attics?
Always be aware of the conditions in your home, generally. Keep the roof/gutters clean and flowing. Ensure all vents/ducting and mechanical systems are functioning correctly. Ensure attic venting is open/free-flowing and adequate for your site and living conditions. If you don’t have an ability or interest in making sure all of these systems are working correctly, periodic inspection by a qualified party like Tim is well worth the cost compared to long-term water damage or mold problems.
About Cleaner Guys
Cleaner Guys is a well-established business in Mount Vernon that provides exceptional cleaning and restoration services. As a fully licensed and bonded general contractor, the company also performs repair and reconstruction work, making it a one-stop-shop for property damage clean-up, restoration and remodeling projects.
The business specializes in water, fire, mold and wind damage restoration for clients in North Puget Sound. Cleaner Guys also offers carpet cleaning, tile/grout cleaning services and general project/site cleaning for both residential and commercial clientele.
For more information, visit http://cleanerguys.com.
A big “thanks” to Bob for his responses!