For years, the industry has used relative humidity as a pest management tool. Experts have talked about the importance of keeping areas dry to reduce pest pressure, especially in commercial accounts, for decades. When psocids emerged as a serious pest of food plants, dehumidification was identified as an important tool to help alleviate this problem.
Only recently, though, has this technique entered the residential market. In fact, our industry was caught flat footed as utilities started to push insulated and dehumidified crawlspaces, especially with dirt floors. Working to stabilize humidity and temperature of crawlspaces and unheated basements would save energy but there was no thought given to how it would negatively influence pest management. If walls were insulated above grade on the inside, there would be no way to see termite tubes or any other pest that might use the hidden areas.
Later, with the explosion of mold mania about 10 years ago, research groups not necessarily affiliated with our industry started working on ways to dehumidify residential dead spaces like crawls and basements. Reducing conditions that would lead to mold had the added benefit of wood-destroying fungus reduction as well as reduction in insect and spider populations.
Rain under the house. For illustration, consider crawlspaces that are found in much of the country. They are still being built today and the Department of Commerce estimates that about a fourth of the homes being built today have crawlspaces. Building codes going back 50 years required that a square foot of ventilation was required for 150 square feet of footprint. If a vapor barrier was installed, that number went to 1 square foot of ventilation per 1,500 square feet of footprint. The intent was to bring fresh air into these spaces to discourage fungus. USDA publications even went so far as to suggest that vapor barriers be installed on bare soil, but that approximately 20 percent of the soil remain uncovered. This would allow some moisture in the crawlspace so the wood would not over dry and twist. The value of uncovered soil has yet to be proven.
So we had, and in many cases still have, codes requiring that you bring in moist air in summer through vents, add in moisture from exposed soil and expect dry conditions. If you think about the crawlspace, you have water pipes usually running through them. What happens when you take hot, humid air and bring it into cooler spaces and let it touch cold sections of metal such as cold water lines? You have condensation — literally rain under a house. As a result of this problem, which then encourages mold and fungus as well as insects and spiders, you have musty air laden with living creatures. One research report showed that 75 percent of air in living spaces had passed through crawls via infiltration or leaking ducts.
Installing a properly sized dehumidifier will greatly reduce moisture in the air in these areas. A musty crawlspace that had that dank odor for years, will in a matter of weeks be odor free. Insects, including those curious camel crickets, will not survive in dry areas and a target relative humidity of below 70 percent can easily be achieved. Some companies also add insulation on walls and a total vapor barrier wrap. Customers have really taken to this service. If you are thinking about getting into this service, make sure that you have the proper materials and equipment. A standard dehumidifier from a big box home improvement store might not do the job. A drain must be installed and the unit must be designed so the coils won’t freeze. Designs vary but the overall goal is the same — dry the air.
The late Bernie Mittelstaedt of Therma-Stor successfully moved our industry to a point where we could embrace this new technology through real data. Bernie singlehandedly was able to get the industry thinking differently about crawlspaces and it was a game changer for the industry.
As an industry that supported ventilation for decades, the question is often raised as to whether it is time to stop installing foundation vents. Vents do have a place and serve to provide fresh air in situations where fungus could be a problem; this is what they were originally designed to do. This new technology, though, may someday be standard practice.
There are no real standards on how to dehumidify a damp space. Some building codes now accept this closed crawlspace technology but some code officials are yet to be convinced of the value. Always check with code officials before installing a system.
Modern technologies such as enclosed crawlspaces can be a valuable tool for customers. The best advice is to do your homework to develop a program best suited for your business and to offer it at a price point your customers will embrace.
Greg Baumann is a technical services director with Orkin (www.orkin.com) and has more than 30 years of varied pest management experience. Learn more via Facebook at www.facebook.com/OrkinPestControl or join the conversation at www.twitter.com/AskTheOrkinMan.