[Mold Control] What's Going on in the Crawlspace

You do not have to be in the professional pest management business crawling through structures’ crawlspaces to determine that these areas have a problem with moisture that leads to far bigger problems: termites, beetles, borers, fungus, rot, mold and — most noticeably — a musky odor. Moisture in crawlspaces also can lead to crawling pests such as ants, roaches and others.

For many years, we in the industry have recommended adding ventilation, ground covers and power vents. This was the correct recommendation, but as houses became tighter due to recommendations from energy departments, the problems continued to be more noticeable; now most authorities in construction, energy and green environments are making recommendations to close crawlspaces and, in some cases, add dehumidification in order to keep the relative humidity in the crawlspace to remain in the 50-64 RH (relative humidity) range and moisture below 20 percent, where moisture will not form and cause or contribute to these unfavorable conditions. Fungus starts to grow at 28 percent moisture, but other surface conditions start at the 20 percent level. The secret to keeping wood from deteriorating is to keep it dry, which can preserve it forever.

The crawlspace encapsulation procedure discussed below affects only the crawlspace and will not be expected to address any conditions above the crawlspace area.

ENCAPSULATION ADVANTAGES. Encapsulation is another way to control the build-up of moisture and humidity that is sometimes associated with crawlspaces. The objective is to reduce the humidity and moisture to an acceptable level: moisture less than 20 percent and humidity between 50-64 percent. This is accomplished by reducing the amount of moisture that is rising from the soil under the crawlspace, and reducing the amount of warm air that is accumulating under the crawlspace from the outside.

Over the years, we have learned that open vents in the foundation wall can contribute to build-up of moisture in crawlspaces. This can result in higher than 20 percent moisture in the substructure of the crawlspace in floor joists and sub-flooring. Over time, this can lead to wood decay fungus. The objective is to reduce the crawlspace moisture by creating an environment of reduced humidity and moisture.

Here’s a look at the procedure we use for installing crawlspace encapsulation:

INSPECTION AND DOCUMENTATION

1. The inspection should start by asking the home-owner several questions about the structure related to moisture and condensation. 
2. The inspector proceeds to the outside of the home where he or she draws a graph of the structure, noting any conducive conditions such as leaking water faucets, downspouts allowing water to collect around the foundation, etc.
3. Next is the crawlspace inspection, where the inspector will observe, take moisture readings, humidity readings and temperature readings (at least six different readings in six different locations are recommended) and post them on the diagram (graph) using a moisture meter and a hygrometer. The inspector will sound the wood and note any evidence of water leaks, wood-destroying organisms and/or damage related to such findings. In addition, the inspector should observe problems with air ducts, water pipes, sewage pipes, electrical problems or foundation problems that a qualified professional in those fields of expertise should look at. The inspector should indicate on the graph by marking the general location where the specialist will place the dehumidifier in the crawlspace.
4. If the inspector has observed a problem in the crawlspace, an inspection inside the home in the area where the problem was observed is recommended to estimate the extent of damage, or if the infestation has moved upward. This would include the attic area if it were accessible. Treatment to the crawlspace may not have any effect on the other parts of the structure.

PREPARING THE JOB SITE

1. The first step in the preparation process is for the specialist to do a quick review of the paperwork and inspect the job site. If there are any questions or problems, the specialist should notify his or her supervisor immediately without alarming the customer.
2. If no problem exists, the target area should be cleared of all debris — not just cellulose, but all removable debris: bottles, cans, stored items or any metal objects
3. Before the actual installation of the polyethylene membrane, any other necessary work should be performed. This includes application of a peroxide cleaner and moisture barrier, application of borates, installation of insulation and termite work. In addition, this work should be done to the proper specifications and/or protocols. Follow these steps when applying the peroxide cleaner (wood and general surface cleaner):

• Fill an empty pail (one with a screw-top lid) with approximately five gallons of fresh water.
• Under gentle agitation with drill mixer add the peroxide cleaner according to label instructions.
• Screw pump assembly onto pail.
• Connect hose and spray wand assembly.
• Connect to power source.
• Apply at an appropriate coverage rate per the product’s label. (Sub-floor surface area is figured at three times that of the “base” floor footprint.)
• Refill and repeat as necessary.
• Scrub with stiff bristled brush any heavily contaminated areas and reapply cleaner to those areas.
• Retain any unused product to use as a rinsing solution for the pump system after the application of the moisture barrier.
• After the 20-minute soak-in time, rinse the cleaned area with fresh water.

Follow these steps to apply the moisture barrier:

• Remove lid and begin blending the product with drill mixer.
• Screw pump assembly onto pail.
• Connect hose and spray wand assembly.
• Connect to power source.
• Follow pump assembly operation instruction.
• Dispense initial product into the pail of peroxide cleaner (flushing lines of cleaning solution).
• Apply at a coverage rate per the product’s label. (Sub floor surface area figured at 2½ times that of the “base” floor footprint). Wall and floor surfaces are direct one-for-one square foot area estimation.

4. The next phase of the preparation of the target area is blocking all foundation openings (foundation vent openings). This is accomplished by cutting a 1-inch thick piece of Styrofoam® board to fit the size of the opening. This piece of Styrofoam should then be placed in the opening and sealed using a clear caulk. In addition to vent openings, any other openings such as pipe penetrations, etc., should be closed using approved materials.

INSTALLATION OF THE MEMBRANE

1. It is important to start with the foundation walls first. Using at least 6-to 10-millimeter polyethylene, the poly membrane should be attached to the lower bottom portion of the sill plate using a button cap-roofing nail with a plastic washer attached. These fasteners should be spaced no more than every 12 inches apart, making sure the membrane is straight and even all across the sill plate.
2. Next the wall membranes should extend down the foundation wall and continue out on the ground at least 24 inches from the footer or bottom of the stem wall.
3. The poly membrane should be used as the ground cover as well, and that membrane should be placed from foundation wall to foundation wall in the target area. The membrane that is positioned over the wall membrane should be anchored with a poly spike no more than every 12 inches along the seams. The ground membrane should be cut to fit around the piers and any chimneys in the target space. The ground membrane also should be positioned under piping and ductwork wherever possible.

DEHUMIDIFIER PREPARATION

1. The dehumidifier is powered by standard 110 volts of electricity, as well as the condensate pump that is needed to extract the condensation from the dehumidifier, so having a duplex power GFI outlet close to the unit is required.
2. If the structure has no outlet close by, one will have to be installed by a subcontractor.

INSTALL THE DEHUMIDIFIER

Install a dehumidifier and condensate pump according to manufacturer specifications. Set the unit to the desired humidity setting of 50-64 RH.

FINAL STEPS

1. Set up and install the sensor and monitor.
2. Install a drain block on the outside of the home.

CONCLUSION. Orkin began offering the preceding crawlspace encapsulation service in 2006, and both we and our customers have been pleased with the results. This service involves a multi-step process and requires significant time commitments. However, if done correctly, it provides good opportunities for you and your company.

The author is senior technical director of Orkin.

Author’s note: The products referenced in this article are not endorsed by Orkin. Orkin is not involved in new construction or post-construction mold control or prevention.

Mold and new home construction

Newly constructed homes are not what come to most people’s minds when they think about mold-infested structures, but new homes are by no means safe from mold.

Dr. Joseph Burley, technical manager, Sostram Corporation, said he’s known of situations where lumber with mold on it had been supplied to construction sites. “Construction lumber is specified to a certain kiln-dried-moisture content (19 percent) but it is not unusual for it to be supplied outside this specification. Wood is, therefore, supplied with a high moisture content, or even sometimes physically wet, to the construction site.”

Specific to crawlspaces, a challenge is construction delays, Burley said. For example, a home’s foundation and sub-floor will be installed and then construction will stop for days, weeks and in some cases months. “Floor joists, the sub-floor and other wooden construction elements in the crawlspace can get very wet at that point and remain wet for a long time in some cases,” Burley said. “You can get a lot of water into the crawlspace that doesn’t get a chance to get out.”

These types of scenarios are reasons why mold prevention in new homes has become a popular service offering from some pest control operators. Sostram offers Mold-Ram, a long-term surface mold and mildew prevention product that is being used in the pest control industry. Sostram has trained distributors on the use of Mold-Ram, conducts technical presentations on the product and offers product literature. For more information, visit www.mold-ram.com.

Different types of moisture

For pest management professionals involved in mold work, it’s important to understand that water is the enemy. If wood becomes wet enough, you will have a fungal problem. If the air is wet enough, you will have a problem. And it doesn’t take long. Most building materials can develop mold in about a week of exposure to wet conditions. It’s also important to understand the characteristics of three types of moisture.

Inherent moisture
In a brand new home, all materials contain water. For example, in the average 2,000-square-foot home, there is an average of six tons of water and it can take six months to dry out. During its first year, a house needs good ventilation or mold will develop.

Weather-related moisture

• Wet lumber can develop mold in less than a week.
• Mold grows on wet construction materials.

Water in buildings

• Rising damp – most construction materials wick water quickly
• Penetrating damp – a leak in the house, like a pipe
• Condensation – crawlspaces that aren’t ventilated or air conditioning systems that are below the dew point will cause condensation, and eventually mold.  “I think the key thing here is that while mold spores are everywhere, the conditions that allow them to grow are moisture, temperature, food source and oxygen,” said Ron Schwalb, national technical manager, Nisus Corporation. “Mold will not grow without oxygen — and the temperature ranges they are designed to live in are the same as ours.”

Schwalb added that while mold is the issue that captures the headlines, it’s important to recognize that moisture can cause decay fungus, which he says poses a dual threat. “It can cause structural damage and can also cause some of the same health concerns that mold growing on the surface causes,” he said.
The preceding information was provided by Nisus Corporation, manufacturers of products such as Bora-Care and Mold-Care. In addition to manufacturing pest control products, Nisus offers a variety of educational literature available on its Web site, www.nisuscorp.com. The company also has a technical team that conducts training seminars throughout the country and is available to provide in-house training to pest control companies. For more information call 800/264-0870.