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How to Create a Mold-Resistant Home

How to Create a Mold-Resistant Home

It’s true: mold exists almost everywhere — in your basement, food, bathrooms, or almost any place you can think of. Even homeowners with energy-efficient buildings designed to promote good health can experience mold problems.

Table of Contents

What Is Mold?

Mold is a type of fungus that forms and spreads on various kinds of decaying surfaces. These tiny spores come in a variety of shades and colors (black, green, white, and brown) and can be found almost anywhere moisture is present, indoors or outdoors.

How Does Mold Grow?

Mold thrives in humid areas and can grow on a number of different surfaces. You might have seen mold growing on your wall, on your carpet, on a block of cheese that’s been in the fridge for a while, or on a loaf of bread you’ve left out too long.

How Does Mold Grow?

Three main conditions are needed for molds to flourish:

  • They must have a food source. This can be human food, but it doesn’t have to be. They often feed on dead organic matter. Mold can also find food in the form of things like:
    • Wood
    • Paper
    • Carpet
    • Glue
    • Grease
    • Textiles
    • Drywall
  • Molds are most common within a certain temperature range. Many can be found growing at temperatures between 60 and 80 degrees Fahrenheit: the same range you’re likely to find in human dwellings.
  • They’re common in places of moisture buildup. You may have seen mold in places where you have a leak. Mold can also be found where water vapor condenses, such as when warm, moist air comes into contact with a relatively cool surface.

Controlling temperature alone may not get rid of molds, because they are hardy and can survive in winter conditions, even when the temperature drops below freezing. Instead of dying, spores may go dormant and wait for the temperature to rise again so they can multiply. This is why controlling moisture is the key to controlling mold.

Energy-efficient homes aren’t necessarily an answer in themselves. In fact, in some cases, having an energy-efficient home can lead to poor indoor air quality, air circulation, and moisture control. For this reason, the environmental impact can be the opposite of what you might expect, at least in terms of mold.

Sustainability and renewable energy are excellent goals, but mold resistance is important, too. The fact is, when it comes to building science, green buildings aren’t always healthy buildings: In fact, they can be quite prone to moisture and mold problems in the years right after they’re built.

Mold-Resistant Building Materials

Mold-Resistant Building Materials

Since moisture is an important element in creating an environment for mold growth, it might sound like water-resistant drywall is a good idea. But it’s important to know there’s a difference between water- and mold-resistant material.

Water-resistant drywall is often called green board; it’s used to resist or reduce moisture and water damage or leaks. Mold-resistant material, meanwhile, is designed specifically to resist and prevent the growth of mold.

Water-resistant drywall is useful, but it still has paper facing, and paper is one material where mold is often found. It’s organic and, therefore, can be used by mold as a food source. Mold-resistant drywall, on the other hand, doesn’t use paper; it uses materials like gypsum board and fiberglass instead and is, therefore, more likely to live up to its name by resisting mold.

Several of the building products listed here, such as fiberglass, have built-in anti-mold chemicals. In addition to these products, you may want to consider products that are GREENGUARD gold certified by health professionals under the LEED (Leadership in Energy and Environmental Design) rating system. The green logo certifies that the product promotes low chemical emissions to reduce exposure to indoor air pollutants like mold.

Mold-Resistant Wood

This product has an added benefit: It also helps keep termites away. Mold-resistant wood is treated with anti-mold chemicals. One such product, made by Frame-Guard®, is GREENGUARD certified not to create any harmful emissions.

Mold-Resistant Insulation

This product allows the wall and floor systems to dry when installed. Fiberglass insulation helps resist any water damage and mold growth. Fiberglass is resistant to mold by its nature, and some companies produce an added layer of protection by treating their products with an EPA-approved fungicide.

Mold-Resistant Drywall

You can use gypsum wallboards or drywall that is water-resistant. Drywall tape may withstand water leaks. Keep in mind that there are several different types of drywall. It can be moisture-resistant, mold-resistant, fire-resistant, or water-resistant.

You want to look for moisture-resistant and, even more important, mold-resistant products. Sheetrock® is one example. Mold-resistant drywall tape is also available.

Mold-Resistant Paint

Mold-resistant paint can help discourage the growth of mold on painted surfaces. However, if there is already mold on the wall, you can’t use this to eliminate it. The paint only prevents the growth of new mold, so painting over mold that’s already there won’t help. In fact, paint applied over moldy surfaces is more likely to peel.

You’ll need to eliminate existing mold before you paint for this strategy to be effective. (You can find low VOC paints that give off few or no volatile organic compounds and are also mold-resistant.)

Mold-Resistant Caulk

Caulk is often mildew-proof and often contains fungicide as well, which helps prevent mold growth, stains, and odors. Mildew and mold are both fungi, but they’re slightly different. They both are found in moist, temperate areas, but mildew tends to be fluffy and lighter in color, rather than slimy or fuzzy the way mold is.

Mildew can also cause health issues, but overall, they tend to be less serious than those arising from mold exposure. As with paint, avoid applying caulk over surfaces that are already moldy. Doing so won’t eliminate the mold.

Mold-Resistant Sealant

This is a protective coating that contains antimicrobial chemicals to reduce fungal growth. It can be used on construction materials such as wood or wallboard to inhibit moisture and, therefore, reduce the possibility of mold growth.

How To Prevent Mold in New Buildings

Choosing the right kind of materials and keeping moisture at a minimum can go a long way toward successful mold prevention in new commercial buildings and homes.

Steps you can take include using mold-resistant building materials and adhesives, insulating pipes to prevent cracks and leaks, and using an HVAC system with filters to catch or prevent mold spores from coming into the home.

In order to inhibit mold growth, keep relative humidity below 65%. Although short-term increases above that level aren’t generally enough to cause mold growth, condensation of water on cool surfaces can occur at lower levels and contribute to mold problems.

Where Does Mold Commonly Occur?

Where Does Mold Commonly Occur?

Unlike plants, which need light to grow, mold can thrive in dark places. It doesn’t need light. As a result, it often grows in areas that may be hidden from the human eye, such as the back of drywall, behind walls and in crawl spaces, inside ventilation ducts, in wallpaper, under tiles, and beneath carpets and carpet pads.

Mold is often found in interior spaces where water is likely to build up. You might find it around water pipes, for example, or in places where water runs frequently such as the bathroom or laundry room. If you take hot showers that cause warm water to contact cool surfaces, this can create the kind of condensation that’s tailor-made for mold.

Basements are another good candidate because they’re below ground, where moisture thrives. But mold can also be found in attics with leaky roofs, as well as areas of building exteriors like roofs, windows, HVAC systems, and walls.

9 Common Types of Mold

  • Ulocladium can be found in kitchens, windows, bathrooms, and basements. It is usually black or gray, and can cause allergic reactions, especially over a long period of time.
  • Alternaria occurs in places like bathtubs, showers, and leaking sinks. It looks similar to Ulocladium under a microscope, and like Ulocladium, it can be black or gray and can trigger allergic reactions.
  • Aureobasidium is a black mold common behind wallpaper or painted surfaces. It’s also frequently found in places that are continually damp, such as shower curtains and kitchens. It can also spoil fruit such as pears, grapes, or oranges.
  • Acremonium is often found in window sealants, humidifiers, drain pans, and insulation. It can appear white, gray, or brown. Not only can it cause allergic reactions, but it can be a source of infection and can create toxins. Because of this, if it’s found in a home or workplace, it should be removed immediately.
  • Chaetomium can occur in places where there’s been water damage such as drywall, wallpaper, and carpets. It’s rarely connected with physical distress in humans but has been associated with conditions such as pneumonia, sinusitis, and emphysema.
  • Cladosporium is a very common kind of mold that can be found in indoor materials such as carpets and fabrics. It can be gray, black, brown, or green. Allergies are the most common health issue associated with this kind of mold.
  • Stachybotrys is a form of mold you should watch out for because it can be toxic. It’s commonly known as black mold because it looks black on surfaces. Places it can be found include basements, attics, and drywall.
  • Mucor is often seen on HVAC systems. You can also find it on decaying fruit and veggies. It looks like long, fuzzy white tufts of hair that turn gray the longer they’re present. Inhaling mucor can trigger asthma and cause problems even for people who are generally healthy. In people with allergies, it can cause an infection called mucormycosis, which affects the eyes, nose, and brain.
  • Penicillin is most commonly known as an antibiotic prescribed by doctors, but that medication was originally derived from a kind of mold. You might find Penicillin in water damage in places such as drywall, wallpaper, and ducting. Even though it can be good for your health when prescribed as a medication, it can also cause issues such as breathing problems, asthma, and sinusitis in its mold form.

How To Prevent Mold in Existing Buildings

According to the Environmental Protection Agency (EPA), the best way to prevent mold growth is to control moisture. Here are a few strategies you can employ to do so:

  • Regularly clean and dry off wet areas within 24 to 48 hours, scrubbing with detergent or soap and water, and making sure it’s thoroughly dry.
  • Fix any leaks you find from outside sources, such as flooding or rain dripping in through leaky roofs, and from damaged plumbing. Dry the area thoroughly.
  • Check your HVAC system to ensure it isn’t contaminated with mold. If you find any problems, it’s a good idea to contact a professional trained in the proper cleaning methods to deal with them. HVAC systems should be shut down before any remediation work is done.
  • Use dehumidifiers to reduce humidity, especially if you live in a high-humidity area.
  • Allow air circulation throughout your home. Open doors and air vents so air can move freely.
  • Discard any porous materials with more than a small area of mold. Unlike non-porous materials such as tile, these can be difficult to clean effectively.

If there has been severe water damage to your home, you may need to reach out to an EPA-certified contractor to do the cleanup and go through restoration.

How Does Mold Affect People?

How Does Mold Affect People?

Mold can lead to health problems in some people and can exacerbate problems in people with existing conditions such as allergies and asthma. It’s common to think of allergies as being related to springtime pollen and animal dander, but many people are also allergic to mold.

Mold can cause irritation in the eyes, skin, nose, throat, or lungs. Reactions include stuffy nose, shortness of breath, red or itchy eyes, and skin irritation. There is no blood test or other clinically proven test to check for mold exposure.

Molds are classified into three types, or levels, of hazard. Class A molds pose direct health threats because they can create toxins or cause infections. Class B molds can trigger allergic reactions, particularly with prolonged exposure over long periods. Class C molds aren’t known health risks.

Large areas of mold can usually be smelled.


Different kinds of mold can create different kinds of health hazards, which is why it’s important to keep your buildings mold-free. Fortunately, there are a number of ways you can do so, ranging from moisture control to the kind of materials you employ in construction and maintenance projects.

Knowing where mold is most likely to occur can help you keep an eye out for problems and address them before they get too widespread. Doing so can keep occupants of your building and visitors healthy for the long term.

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