In-Floor Heating Creates A Pest Paradise Below The Slab

While most pest management professionals are familiar with a pest’s view of the world above the ground floor slab of a ranch house, they may be less aware of the environment that exists under it.

The slab serves as a roof over a mixed profile of disturbed and natural soils that are covered with a bed of various fill materials. This can be an attractive site, not only for the original inhabitants of the soil, such as ants and termites, but also for rodents and other animals. The attraction is increased by the abundance of shrubbery, litter, mulch excessive moisture and protection from extremes in the weather. Root systems of past generations of foundation shrubbery and roots of trees, long since removed from the site, can also provide food for termite colonies for years before termites need to forage for the “tree parts” above the slab.

Utility pipes buried in the soil serve as guides for the termite and ant scouts. They are constantly searching for food and shelter for expanding populations. Access to new sites above the slab is readily available through expansion joints around the inside perimeter and breaks under partitions.

Rodents also find the slab to be a safe and convenient canopy for their burrows, close to food and water. Other pest species such as ants, sowbugs, etc., can find the utility openings to be an easy entrance to sites above the slab.

NEW CONSTRUCTION PRETREATS. Pretreating in the 50’s and 60’s with chlordane/heptachlor, even at “dishwater” concentrations seemed to inhibit subterranean termites to a remarkable degree. Some termite operators in South Florida admitted they had few termite calls in housing developments where treatments had been performed by cut-rate operators.

With the demise of the chlorinated hydrocarbons and the use of organophosphate compounds, the days of dilution to below-legal rates spelled trouble for some termite operators. Because new toxicants are generally less tolerant of high pH soils, callbacks increased, especially when less than label dosages are used. This problem may be caused by higher pH conditions in the soil. In many areas, limestone bedrock and higher water tables compromise the longevity of conventional termiticides. In addition, the pH level in many municipal water supplies is elevated, according to a water authority official in my community.

AN ADDED COMPLICATION. Now a new phenomenon in the building industry may complicate the termite operator’s efforts to control subterranean termites. Radiant hot water heating, described in the January 1997 issue of Popular Mechanics, is gaining widespread popularity among builders in the northern half of the United States. With the Hydronic in-floor heating system, heated water flows through tough cross-linked polyethylene tubing that is buried within the slab. The coils are usually embedded in a cementitious matrix poured over high density foam insulation board. While the insulation reduces the temperature to a great degree, water heated to from 110°F to 140°F will eventually increase the temperature of the fill below to some extent.

With the new system, most of the heat does not end up near the ceiling. There is only a two- to three-degree difference between air on the floor and ceiling. Objects in the room are heated, not the air.

It is a Myth Conception that this new development doesn’t affect the conventional methods for treating termites. According to chemist Sam Creeger, formerly a section head with the Environmental Protection Agency, it is a rule of thumb that chemicals, including termiticides, break down faster with an increase in temperature. This rule of thumb states that with every degree Celsius rise in temperature, chemicals in a moist environment break down 10% faster. For 10 degrees difference it breaks down two and half times faster, according to The Handbook of Chemical Property Estimation Methods, published by the American Chemical Society in 1990. This will have a profound affect on any soil treatment with current termiticides that are used in structures with Hydronic in-floor heating.

Because moisture and heat have been proven to attract subterranean termites, an increase in termite activity can be expected. Above the slab, without hot air, a change in humidity can favor some moisture-sensitive creatures, such as the house dust mite.

Household ecology ain’t what it used to be.

Harry Katz is a contributing editor to PCT magazine. He may be contacted at Berkshire E-3076, Deerfield Beach FL 33442, 954/427-9716 (both phone and fax).