Mold Prevention

There is no point in “cleaning up” or “removing” mold if the underlying causes of a mold problem are not also addressed. Unless the causes, such as leaks or high moisture are corrected, mold will simply recur. Band-Aid approaches like trying to “kill” or “prevent” mold by using chemical sprays, coatings, or air cleaners are insufficient and ineffective at preventing future mold and in some cases these approaches create their own hazards.

  • Attic Condensation and Ice Dam Leaks: If roof leaks or attic moisture condensation due to a combination of inadequate attic ventilation and a building moisture source (wet basement, plumbing leaks, roof leaks) cause excessive moisture or actual wet conditions in an attic, conditions are ripe for extensive mold growth.
  • Visible mold may appear on wood surfaces in an attic such as on rafters or roof sheathing.
  • Hidden mold may be present and may be even more of a problem if it forms in insulation or in the ducts and air handler of an air conditioning or heating/air conditioning system.
  • Mold from an attic might be a problem on lower floors: Typical building air convection currents tend to move air up and out from lower to upper building levels, so one would not think that much mold would move down from an attic into the living area. But important exceptions to this can quickly move problem mold from an attic into a living area.
  • Conditions moving mold downwards from an attic include the following:
    • Mold growth in HVAC ducts or air handlers found in an attic
    • Mold on any attic surface or in attic insulation if it is a species producing airborne spores and if the building uses a whole house ventilating fan, especially if there is inadequate exit venting for the fan operation. This condition pressurizes the attic and moves mold down through various openings into the floors below.
    • Mold on building surfaces in an attic or attic knee wall space which opens onto or has a knee wall common with an upper floor living space such as a bedroom.

Building Exterior Leaks and Mold No mold cleanup project will be successful unless you correct the conditions that caused mold growth in the first place


The photograph shows a double problem

An expert inspection and report should find and suggest remedies for site and building exterior conditions that produce mold or for building areas that serve as a mold reservoir or as amplifiers for allergens, mold, mildew, excessive pollen or pet dander.

The basic steps: find all unwanted moisture sources, correct appropriate building, site, landscaping, & construction details. 90% of the wet basements and crawl spaces I see are caused by bad or missing roof gutters and downspouts.

An environmental investigator who has training and experience in building science, mycology (mold science), and IAQ, or in some cases an experienced ASHI-Certified home inspector or sick building investigator who is who has a similar in-depth understanding of construction failures can be helpful at this step.

  • Building Interior Leaks and Mold:address interior conditions that produce or serve as reservoir or amplifier for common allergens: mold, pollen, pet dander as well as other possible respiratory irritants such as latex, paints, product off-gassing furniture or carpets, and renovation hazards such as lead paint or chemicals or other environmental issues.

The photograph shows extensive staining from protracted plumbing leaks in a house that was left unattended. The result was extensive basement mold requiring demolition and cleaning of large area of the home.
  • Plumbing leaksthat are unattended, water running under kitchen or bathroom cabinets when fixtures are in use, and air conditioning system condensate leaks into the building or into the HVAC duct work are examples of indoor leaks that can lead to a mold problem if not promptly addressed.

Indoor Humidity Control: What indoor humidity should we maintain in order to avoid a mold problem? The answer depends on the climate in which you live. In the Midwest where temperatures and humidity levels range widely, a set humidity level is not ideal. In addition, moisture levels will vary from room to room in your home. The best approach is to wrap your home with a water-shedding, breathable housewrap, and let your internal humidity levels match those outside. It is less comfortable, but it will be much better for your home. Whenever a home’s internal humidity is significantly different from that outside, moisture will travel through the home’s walls, moving from wet to dry. This can result in moisture trapped inside of walls where it may not be able to escape without the right conditions outside. As a general rule, indoor relative humidity should never be set higher than 50%, but that level should be allowed to increase naturally through interaction with the outside environment. Opening windows is the easiest way, but increasing the amount of fresh air in your HVAC system is another solution.

  • Central HVAC systems, in addition to providing fresh air to your home, can be equipped with filtration that can substantially reduce the level of indoor airborne particles. Their effectiveness can be increased further still if the system permits the fan and filtration to run continuously.