Mold Prevention Guides

Mold Prevention Guides and Tips

Pointers from Leadsafe Environmental

1. Ice dams, during cold and snowy winter-make sure all gutters and downspouts are kept clean and free of ice and snow. We have seen many houses with water damage due to ice dams this year.

2. Check all hose and fittings on washing machines, replace if old, leaking or kinked and turn water supply off if leaving for extended times. Remember, mold will start to grow in as little as 24 hours when moisture is present.

3. If basement walls are finished with sheetrock, install vents near the floor and ceiling to allow air flow within the walls (the more vents the better). If installing sheetrock in a basement below grade (not recommended), raise the sheetrock a few inches up off of the floor (sheetrock acts like a sponge).

4. If you have storm windows, makes sure the weep holes have not been painted over. Weep holes allow for water to drain out from behind the storm window and the interior window.

5. With the melting of all the snow from this past winter, make sure all basement floor drains are clean and of course, free of debris.

6. Check the ground around the foundation to make sure the water is running away from the house and not down a cellar window or bulk head.

7. Before the cooling season starts, check central air systems. Make sure the water tray is clean and the drain is free of debris Also clean or change air filters.

8.Spring is a good time to check the roof to ensure the harsh winter has not loosened shingles and flashing around vent pipes and chimneys.

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Mold Prevention Tips

Clean and dry wet or damp spots and wet, non-moldy materials within 48 hours.

Four words summarize what has to be done to effectively, efficiently and safely remove, remediate, and decontaminate molds:

(1) CONTAIN the molds from spreading into uncontaminated areas;
(2) KILL the molds;
(3) REMOVE the dead molds; and
(4) PROTECT the cleaned out areas against future mold infestations.

Fix leaky plumbing and leaks in your building as soon as possible.
Watch for condensation and wet spots.
Do not allow sprinklers to hit buildings.
Inspect and repair window seals and flashing.
Vent moisture-generating appliances to the outside where possible.
Perform regular building/HVAC inspections and maintenance as scheduled.
Monitor moisture problems to prevent mold growth.
Stop and repair sources of water intrusion or accumulation immediately.
Prevent moisture from condensation by increasing surface temperature or reducing the moisture level in the air . To increase surface temperature, insulate or increase air circulation. To reduce the moisture level in the air, repair leaks, increase ventilation (if outside air is cold and dry) or dehumidify (if outdoor air is warm and humid).
Keep heating, ventilation, and air conditioning (HVAC) drip pans clean, flowing properly, and unobstructed.
Maintain low indoor humidity - below 60 percent relative humidity (RH), ideally 30 to 50 percent if possible.
Don't let foundations stay wet. Provide drainage and slope the ground away from the foundation.

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Mold Prevention

The most important consideration to keep in mind for preventing toxic mold is that fungi and mold need a moist, wet, or damp environment in order to thrive. By maintaining a clean, dry home or workplace, dangerous mold species cannot begin to grow. Unfortunately, it is often extremely difficult to distinguish between toxic molds and those that don’t pose a risk. Most types of mold appear quite similar---black or gray sooty patches. The good news is that even if toxic molds are in or around a home, most homeowners remove them through normal cleaning before they are able to grow to a size where they would pose a threat.

Regardless of the type of mold that is found in a particular home, the relative safety of those inside depends on the size of the mold manifestation. The danger level occurs when mold reaches a size of roughly 2 square feet. Also of concern is if mold has infested household items like insulation, drywall, or carpet. If so, these materials should be immediately extracted and the source of the dampness or wetness should be fixed. When replacing these items, it is best to use a non-cellulose and low nitrogen replacement material.

If the mold patch is small, it can be removed with a chlorine-bleach solution (1 cup of bleach in 1 gal. of water). The mold should come off with simple scrubbing (individuals should protect themselves with eye protection, rubber gloves and carbon filter respirators). Mold that has dried should not be scraped because this greatly increases the chances the releasing toxin-carrying spores into the air.

Sources in and around homes that can create a dangerous environment include leaky or broken pipes, windows or older doors that lack good seals, roofs that leak, and any cracks or holes in the building. If flooding has occurred, it is extremely important to make sure that the water is thoroughly dried up to avoid festering water or dampness. In addition, reducing the humidity through the use of a dehumidifier can prevent the growth of dangerous toxic molds.

All buildings should undergo scheduled maintenance that includes inspection for water leaks, problem seals around windows and doors, as well as checks for visible mold in moist or damp parts of the building. Any conditions that could be a possible cause of mold or fungi growth should be corrected to prevent possible problems in the future.

Mold Prevention: Trades Can Work Together

By Bruce M. Small, P.E.

The mechanisms of mold growth

Many published articles (e.g. Toxic Mold: A Common-Sense Approach to an Uncommon Challenge, Walls and Ceilings, July 2002) have described mold’s need for moisture. One of the primary purposes of a building is to prevent moisture from intruding in our lives—we all prefer a roof that doesn’t leak. Well-built and well-maintained buildings don’t get wet inside.
Still, many buildings do get wet inside in a number of different ways:

• Water can fall or drip in from leaks in the roof or exterior walls (by gravity).
• Water can be sucked in through exterior materials that are exposed to rain (by capillary action) or through basement materials exposed to wet earth.
• Moisture-laden air can be blown in (or out) through cracks in the building envelope (air leakage).
• Water vapor can wander in and out slowly by diffusion, molecule by molecule, as it moves from a more humid area to a less humid area.
• And, of course, water can also be spilled (plumbing leaks, sloppy kitchen work, playful children in bathtubs, plant growth, faulty appliances, excessive mopping, fire fighting, etc.).

The challenge for any building designer and owner is to exclude, deflect or otherwise harness all of these moisture flows so that they don’t cause damage. In actual practice, it turns out that a combination of common sense and modern building science can effectively meet this challenge.

How do buildings end up moldy?

The problem is that it takes only one small mistake to cause a moisture problem inside a building. Sometimes, mistakes are made when a building is designed. For example, a missing roof closure detail can allow rain to enter a building under adverse wind conditions. Or designs that work well in one climate are mistakenly applied in another (e.g. houses designed for operating in cold winter conditions don’t make good houses for air conditioning in humid southern climates).

Sometimes, the building design is excellent, but the contractor doesn’t follow it closely enough and mistakes aren’t caught by the architect or building inspector.

Some school buildings, for example, have developed moisture problems because the pavement grade in the surrounding play area was allowed to slope toward, rather than away from, the classrooms.

Sometimes, buildings are used for purposes other than for what they were originally designed. A building, for instance, formerly used for cheese making or flower cultivation, may lack adequate ventilation when it is converted for an industrial or hobby activity.

Good buildings fall into disrepair because of declining budgets, absentee landlords, mismanagement or other reasons. Case in point—some schools have high humidity and poor indoor air quality because ventilation fans or exhaust vents have broken and have not been repaired.

Why use a systems approach to building design?

Mold arises in buildings because many people do things without looking at the bigger picture. “Building science” and “systems approach” are words used to describe a new way of designing, building and operating buildings that keeps a steady focus on the total performance of a building.

The University of Toronto’s Building Science Program emphasizes in its continuing education literature that failure to consider the bigger picture can lead to building failure: “Schools of engineering typically teach building science in a fragmented manner, consisting of discrete elements of material science, structural design, mechanical systems, etc. Schools of architecture typically take a more integrated approach to teaching building design, but subjects related to building science are often viewed as too technical in nature. This has left an education gap within the ranks of engineers and architects practicing in the construction industry, where the building must be considered as a system. When the interaction of the many different elements and components of a building and the environments to which they are exposed are not considered as a whole, building failures can and do result.”

The systems approach to building science acknowledges the interdependence of the component materials, the mechanical and electrical systems, how the building is operated, how the environment affects the building and how the occupants use the building.

In a systems approach, building designers attempt to understand the operating characteristics of each part of the building and of the building as a whole. Changes aren’t introduced in one component material or subsystem without evaluating their impact on other aspects of a building’s overall performance.

In a well-designed building, all the materials and subsystems knit together to ensure the whole building works well, similar to a “team approach” in sports. This can be accomplished in practice by establishing good communication among all the designers, builders and potential users of a building, so that no person can change any one aspect without considering its impact on the rest.

For example, cutting school maintenance budgets in order to save a dollar now can lead to significant human illness, further expense and considerable disruption. Choosing the cheapest materials and building envelope designs can drastically reduce the useful life of a building, through wall deterioration from moisture transport, condensation and mold growth.

Sometimes, moisture-impervious finishing materials are used in air-conditioned spaces within air-leaky buildings in warm humid climates, to make walls easier to clean. Using them in this application, however, can trap moisture inside the wall causing mold growth and drywall failure over time. In short, quality buildings require lots of good thinking, before they are built and after the occupants move in. Take shortcuts at your own peril.

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Guidelines to avoid mold growth

Use a full rain-screen around the entire building. It sounds simple but there’s an art to making a building shed every bit of rain possible. Adequate protection is required in the outer building layers so that driving rain will not penetrate the building. This requires appropriate rain-screen materials and additional flashing to direct any water that might penetrate under severe weather, back to the outside through a “drainage plane.”
Building scientists like Joe Lstiburek, of Boston, emphasize that nothing is perfect. One should expect some water leakage and design a building to direct it back out, so it will dry out again.

Buildings work best when there is good foundation drainage, good guttering around the roof, and proper sloping of all ground surfaces and walkways away from the building, so that water won’t be directed into the building below grade. Inside, adequate drainage is a must in areas that use water—for example, a laundry or utility area. If the water table is high, a building may also need one or more sump holes and pumps, which activate in an emergency to keep water from entering a basement below grade.
Older-style construction allows a great deal of air leakage through outside walls and ceilings (the building envelope). People used to think this was a good thing because it provided air for the furnace and helped to dilute indoor pollutants. But air leakage through the building envelope can allow moisture to condense within the walls and ceilings, depending on the outdoor temperature and humidity. In northern (winter) climates, moisture-laden air going out through walls can cause condensation when it reaches the cold outer layers of the wall. In southern climates, warm, humid outside air leaks inward and can cause condensation when the air reaches air-conditioned materials inside (e.g. the backside of drywall, or cold air-conditioning ducts).

Modern buildings use direct-vent furnaces, tight wall construction, low-emission materials and deliberate ventilation rather than air leakage through walls and ceilings. If there is a proper air barrier in all walls and ceilings, there is no way for moisture-laden air to move back and forth across the “building envelope.” Without such moisture transport, there can be no condensation and mold growth within the walls and ceilings.

All buildings need ventilation to remove stale air and excess moisture produced during the normal activities of daily living. Without adequate ventilation, moisture and indoor pollutants accumulate. With leaky construction, ventilation may be adequate to remove pollutants but may lead to condensation and mold growth. With tight-wall construction using low-emission materials, ventilation can be much more efficient and is often combined with energy recovery in an exchange between intake and exhaust air.

Using a systems approach and designing high-quality buildings was once a very cumbersome and expensive proposition (although never more expensive than building failure). Today, we have access to new materials and methods that make it easier to apply the principles outlined above and to achieve mold-free buildings.

Overturn old building mold practices

New approaches to building that will prevent mold growth are challenging mold conventional building practices throughout North America. For example, it used to be standard practice in warm humid areas, to put the air-conditioning equipment and ducting in the attic and then ventilate the attic so that it wouldn’t get unbearably hot.

The problem with ventilating with warm humid air is that the moisture seeks out any cold surface (e.g. . an unwrapped A/C duct) and condenses. Months of dripping lead to mold growth in the insulation and drywall beneath. Eventually, the entire attic and ceiling require fixing. Some manufacturers recommend the newer practice of sealing

the attics in humid climates and applying soft-foam insulation to the underside of the roof, forming a cathedral ceiling. This turns the attic into a dry, conditioned space, significantly improving the efficiency of the air-conditioning and preventing condensation and mold growth.

Designers and building code regulators are also being challenged to rethink their insulation guidelines, which used to include ever-higher thicknesses and R-values in the colder areas of the continent. Since the value of insulation is defeated by airflow through it, it makes sense that adequate insulation in a well-sealed wall may be just as good or better than much more insulation in a wall that leaks like a sieve.

Hotel owners in southern U.S. regions used to curse the fact that vinyl wall coverings had to be replaced every few years. Why? Moisture leaking through the building envelope from the outside would penetrate the drywall and condense within it, right behind the wallpaper, which was impervious to moisture. Inevitably, the back surface of the wall covering would become black with mold growth and begin to peel. Owners would rip it off, scrape it down and install more of the same.

Now that there is greater understanding of moisture flow, condensation and the dangers of mold growth, people are also rethinking the concept of vapor barriers, which must be on the warm side of the insulation, not the cold side.

If you put a vapor barrier on the wrong side, or on both sides, moisture may get trapped and the wall between may never dry out. If a good vapor barrier is used in the right place (warm side) in combination with a well-sealed building envelope, there is very little moisture transport across the wall or ceiling.

In a properly designed wall, any residual moisture that does pass through or around the vapor barrier can continue through the wall by diffusion and causes no harm

In warm climates, small amounts of residual moisture can, for example, be easily handled by the drying effect of air conditioning if the moisture is allowed to migrate completely through the wall into the interior space. In cold climates, residual moisture can reach the exterior without causing damage, if the outer layers of the wall are permeable to moisture flow.

As long as the walls and ceilings are sufficiently airtight, we are not as dependent on vapor barriers as before to avoid condensation and mold growth. In fact, in some climates and applications, vapor barriers may turn out to be unnecessary and even undesirable.

Remediate existing buildings

Just as mold growth can be prevented in new construction by prudent design, good thinking and lots of co-ordination among the many parties involved, buildings that have developed mold problems can be properly remediated, if appropriate care is taken. The following example illustrates how moldy buildings can be returned to use.

Problems were encountered soon after the occupation of three intermediate schools in Texas in the form of flare-ups of mold allergies. Mold was first discovered behind wall hangings and marker boards in several rooms. An investigation revealed numerous flaws that allowed water to penetrate into the walls.

The consultants recommended that all existing materials containing mold should be removed and that the existing exterior building envelope be modified to provide for the proper control of moisture entry, accumulation and removal.
Repairs were made to the roof, gutters, downspouts, grading, windows, flashing and weep-holes to ensure that rainwater could no longer penetrate the walls or roof.

The moldy inside walls were removed and both the interior and exterior surfaces of the exterior masonry walls were moisture-proofed. Three inches of foam insulation were applied directly to the inside face of the exterior masonry veneer and then the interior walls were rebuilt.

The cardinal rule in avoiding involvement in a lawsuit is: “Don’t do anything you know is dead wrong.” Painting over moldy drywall in the hope that the mold will go away is one such example. Installing the wall finish before the roof is sealed is another. In buildings, covering up mold problems just doesn’t work—mold will continue to thrive and will rise to the surface again, literally.

Subcontractors won’t shoulder the full responsibility for the building’s overall performance, but their reputation may still suffer if others haven’t done their job properly. The finest drywall job can be ruined overnight by leaky windows. The most decorative ceiling can be marred in minutes by a plumbing failure. Specifying vinyl coverings in the wrong application won’t help the wallpaper installer market his expertise. And all contractors lose credibility if the building goes moldy. W&C

Reference: Bruce M. Small, P.E., is co-founder and director of the Envirodesic Certification Program, which develops and promotes buildings, products and services that contribute to healthy indoor environments.

More Mold Prevention Tips

Mold Advice & Help

1. Hire a Certified Mold Inspector or use our Do-It-BEST-Yourself mold test kits for mold mildew mold inspection and mold testing for various types of mold to find and identify mold in homes and houses, mold spores, black mold, black mold toxic, other toxic molds, water mold, other dangerous molds, household mold, basement mold, attic mold, heating-cooling duct mold, and crawl space mold.

2. Hire a Certified Mold Remediator or use our Do-It-BEST-Yourself mold products for mold in home problems, mold cleaning, to kill house mold, mold abatement, mold remediation, mold removal, and mold prevention.

3. For mold training, mold education, and mold certification, visit: Mold School.

4. If you are experiencing black mold symptoms, other mold symptoms, a mold allergy, symptoms of mold allergy, or you want to see black mold pictures, visit Mold.