Home Improvement
Old Homes: Mold and Mildew Retrofit

Old Homes: Mold and Mildew Retrofit

January 3, 2007

By Guest blogger, Mindy Pennybacker

The Green Guide #69

Buildings seldom manifest sickness as completely as Poe’s House of Usher, which finally sank into a mire, but the occupants of an unhealthy house can often feel that things are heading that way.

When Karen and Tom Jung bought their Verona, New Jersey woodframe cottage, built in 1945, they didn’t anticipate any major work. The roof, ceilings, walls and floors were in fairly good shape.

“We knew the basement was damp, but there was no standing water, and we aired it out before moving in,” Karen says. Within a year, the Jungs’ younger child Ben, then two years old, began coughing and wheezing. “We worried that Ben would develop asthma, and his eczema got worse,” says Karen, whose asthma also worsened.

When their doctor said that mold, a potent allergen, might be provoking these reactions, the Jungs tested their indoor air with mold plates, which contain a culture on which airborne spores, or colony-forming units (CFUs), can grow. “Ten to twenty CFUs is medium, and anything above twenty is high,” says Wayne Tusa of Environmental Risk and Loss Control in New York City, which tests homes for pollutants.

“Molds and mildew thrive in humid, inadequately ventilated areas such as bathrooms, basements and sometimes closets, and can migrate throughout the air of a house or apartment,” says John Bower, author of The Healthy House. Although the rest of the house didn’t look or feel moist, “We found significant mold in every room, on every floor,” Karen says.

The Jungs hired Paul Novack, owner of Environmental Construction Outfitters (E.C.O.), a supplier of least-toxic building and decorating products in New York, to rid their house of mold. Due to the ground’s high water table, water was seeping into the basement floor and pooling in the hollow concrete-block walls. Moisture rose into the airspace between walls on the upper floors, breeding more mold.

First, Novack installed a dehumidifier in the basement. Then he completely isolated the upper floors from the basement, sealing floor cracks and wall openings, such as gaps at baseboards, around light switches and pipes, and behind or under cabinets. He bored “seep” holes in the basement’s concrete walls, and dug a trench along the perimeter of the interior walls. “Water just flowed out of the walls,” Novack says. The water now runs into a sump-pump well and is pumped into a drain. On the basement’s concrete walls and floors, Novack sealed out moisture and kept volatile organic compounds (VOCs) locked in with Penetrating Water Stop.

A second mold source was a toilet leaking into the floorspace beneath Ben’s second-floor bedroom. Again, the way to combat mold was to remove humidity – this time, through stopping the leak, and ventilation. “We opened up the ceiling of the room beneath the leak to dry it out,” Novack says.

To help prevent further mold infestation, Novack cleaned the exterior cedar-shingled walls and wood deck with a borax-derived cleaner, called Wood Renew, that kills mold and mildew, then coated them with Proguard sealant. After six months, Novack ran mold plates again to make sure that the mold was gone. The house had lost its musty smell, and the Jungs say they’re breathing easier.

To maintain this low-mold environment, “Use air conditioning and/or dehumidifiers, and ventilate,” John Bower advises. For other mold prevention and clean-up strategies, see Mold and Moisture Control.