Information on moisture and mold control

The following is information on general prevention to keep buildings moisture free and dry.

Use an air conditioner / dehumidifiers / air circulators in the spring and summer (rainy season and hot humid months) and a dehumidifier whenever the outside temperature is cooler, such as fall and winter. Both of these remove moisture and will maintain a lower humidity level inside of the building, which mold requires in order to grow in the first place. These should be set to maintain the moisture(humidity) level at 45% or lower. Ideally, 40% or less is best for mold prevention. Also use of air circulators or fans to keep the air moving.


Understanding how environmental conditions (weather) can cause mold growth in a building is a step closer towards prevention. In short, everything is based on one thing, keeping the moisture (humidity) level down or out of the building altogether. This is accomplished by the following:

I. Keep all openings (windows, doors, etc.) closed whenever it is raining or humid outside.

2. After an extended period of rain and the house feels damp, do not open up the house if it is going to be humid outside. You will only create an incubator for mold growth.

3. Use “Mechanical Drying and Moisture Control” whenever it is raining or humid outside. This means that you keep the building closed up and use air conditioners or dehumidifiers to remove and control the moisture (humidity) level inside. Running fans to circulate the air increases the efficiency of a dehumidifier or air conditioner, as well as provides additional comfort for occupants.

4. Introducing fresh air into the building is important, however you must manage when and when not to do this. Only when the weather is nice and sunny and there is low humidity should you open up the building and air it out.


Mold contamination in an attic is caused, the majority of the time, by one or more of the following:

I. Inadequate ventilation

2. Lack of insulation between the attic and rooms below allowing moisture to enter into the attic.

3. Appliances (dryers and bathroom vents) being directly vented into the attic.

Corrective measures:

(I) Evaulate the required ventilation in the attic

(2) Add more insulation to the space between the attic and rooms below. This will prevent the warm air below from rising into the attic and mixing with cooler air, causing condensation.

(3) Ensure that the vent hoses from a dryer or bathroom fans do not vent directly into the attic. They should be vented to the outside. (Discussed in more detail under “Appliance Vents”)


Below are some options and advise for prevention whenever the building is built on a cement pad:

Ensure that the ground around the building is lower than the outside siding and the top of the cement pad.
Ensure that water can drain away from the building and that there are no water traps that can cause water to penetrate inside of the building.

Install another form of flooring other than carpeting, such as vinyl tile or linoleum, especially in high moisture areas such as bathrooms.
If you choose to install carpeting, consider a direct glue instead of carpeting over padding. This will at least minimize the airspace under the carpet and not provide a dark, damp space ideal for mold growth. Direct glue carpets can release a lot of the moisture coming from the cement and not provide that dark, damp cavity. It is better to go with a synthetic commercial carpet rather than a thick plush one.


It is essential that moisture in a damp basement be kept under control. This can be accomplished by different means.

(I) Dehumidifiers. Install more dehumidifiers. The size of your basement and the level of dampness will determine how many dehumidifiers are needed to control the moisture level.
(2) Exhausting Moisture Buildup. You can also try increasing the ventilation in the basement by:
Installing fans blowing to the outside to remove moisture buildup.
Install a power vent system that also has a temperature and humidity sensor that will engage the system automatically when needed.


Buildings with dirt floor basements tend to be older (100 yrs old, etc.). These buildings were constructed of old growth lumber which could withstand the moisture of the old root cellars. Although mold problems do develop in the basements of these old building, it is rare. The problem usually begins because the building has had some renovating done to make them more energy efficient. Modern building materials (todays softwoods and plywoods) do not have the moisture resistance properties as the old growth wood and becomes an excellent food source for mold. Crawl spaces can be found in any home, old and modern, and usually has a dirt floor. Basically, the same problem as with dirt basements applies. Both of these situations present a problem. Unless major steps are taken to prevent moisture from getting into the dirt, the dirt is going to stay damp. Realizing this, the prevention methods can only be an effort to minimize the amount moisture that remains in the basement or crawl space. The methods will have to be a combination of improved ventilation, continuous air flow, and moisture removal from these areas.


Finished basements can add additional living space to a home, however it can come with a price. In the spring (rainy season) and summer (hot & humid) the cement is going to absorb the excess moisture and release it inward. Unfortunately, this moisture buildup is unseen behind the finished walls. Inside of the walls is a dark, and now damp place with no air flow. This is ideal for mold growth. The next problem is that the mold growth is hidden and may take a long time before it works its way through the materials to become visible. In the meantime, occupants may be experiencing mold related health issues without knowing it. Once the mold becomes visible inside of the room, it is likely that there is major mold growth inside of the walls. If there is carpeting with a pad over the cement floor, the same thing applies. Usually the pad is saturated with hidden mold long before it becomes visible on the top of the carpet. Every time someone walks on the carpet it releases mold spores into the air, unknown to the occupants.

Remediation of the mold in this case usually means gutting the finished areas. That means removing carpeting, padding, walls (sheetrock, paneling, etc.), insulation, and possibly the studding. If the studding can be cleaned, it should be scrubbed down along with the cement with a fungicide detergent solution. After complete mold removal, all surfaces should be thoroughly dried using air movers and dehumidifiers. After complete drying (verified using moisture meters), the area should have an “Air Quality and Surface Sample Test” done to verify complete removal of mold.

Reconstruction can now be done.

The following are some suggestion to prevent the same thing from happening again:

(I) Move the studding out away from the wall so that there is an air space between the wall and cement.
(2) Build in to the area a place where a fan can circulate the air around the room in the air space between the wall and cement.
(3) If you want carpeting, install a synthetic (Nylon or Olefin) commercial type carpet without a pad, direct glue method on the cement. This eliminates any pad absorbing and holding moisture from the cement and growing hidden mold. A better solution would be to install a vinyl tile floor or linoleum and use area carpets or rugs that can be taken up to air out.
(4) Do not use Craft-Faced insulation, if insulation is required, use styrofoam sheets.
(5) If installing sheetrock on the walls, make sure to keep the sheetrock up off the floor about 2 inches toprevent any moisture from the floor wicking into it.
(6) If building with wood, make sure to use pressure-treated lumber for the wall sill plates.
(7) An alternative to wood is to use the modem aluminum studding and sill plate track system. There is noway for this to absorb moisture and become moldy.

Once reconstruction has been completed, you must implement prevention methods as outlined in the “General Prevention” paragraph, by installing and using dehumidifiers, or air conditioners, to keep the moisture (humidity) levels down and under control.


(Clothes Dryers, Bathroom Vent Fans, Stove Hood Fans, Propane Heater Unit Vents) All of these need to be vented to the outside. Having any of these venting directly inside is asking for a mold problem. A common practice in newly built homes over the past few years is, to have dryer and bathroom fan vents going directly into the attic. Even with excellent attic ventilation, this usually creates a mold problem. Hot-moist air is being pumped into this area. Even in the winter this creates a problem because that hot-moist air mixes with the cold air and creates a condensation issue. The roof sheathing and rafters are constantly being soaked, frozen, and thawed by this condensation. We have noticed a major increase in mold contamination calls in attics over the past couple years, all in newly renovated or built homes where appliances are vented directly into the attic. In Basements, where a lot of people have clothes dryers directly venting into the basement, creates excessive moisture buildup and leads to mold growth. Propane Heater Vents must be vented to the outside away from soffits so that the moisture can not be drawn back into the attic, causing moisture buildup.


Mold growth problems are triggered from a water intrusion problem. Sweating toilets or pipes. A common cause of mold is pipes and toilets sweating in the hot-humid months. In many cases, the use of an air conditioner eliminates this sweating problem, which in turn eliminates the condition that mold requires to grow.

Water Damage. If you have a water damage, regardless of how minor you may think it may be, it is essential that it be taken care of immediately. All wet areas must be completely dried as fast as possible. The longer materials sit wet or damp, the higher the risk of developing mold. Mold can develop as soon as 48 – 72 hours.