Charlotte homeowners battle hidden humidity by sealing crawl space
Moisture in a vented crawl space causes multiple problems. Sealing the vents and laying a vapor barrier helps prevent damage. Photos courtesy of Ron Weatherly
Angie's List member Dan Ritchie received good and bad news from the termite inspector he hired to check out his Stanley, N.C., home. The good? The inspector found no termites eating away at his home's foundation. The bad? The moisture in his crawl space did threaten to undermine the structure.
Ritchie says the inspector told him his crawl space was one of the most moisture-damaged he'd ever seen, with the wood rotten to the touch. "I knew my crawl space humidity was high, but I had no idea what damage it could do," he says. "I'd never heard of dampness being a structural concern."
He hired highly rated Dry-Pro Basement Systems in Charlotte to replace the damaged wood, put down a vapor barrier, and install a dehumidifier and humidity-monitoring system at a cost of about $18,000. "The moisture is controlled now," Ritchie says. "But this was an extremely expensive lesson for me to learn."
The problem under Ritchie's home isn't unusual in North Carolina or the Southeast, where crawl spaces and high humidity are common, says Tim Hodges, co-owner of highly rated AccuDry in Charlotte. "Crawl spaces are the perfect breeding ground for all kinds of things you simply don't want," including damp insulation, mold or wood rot, Hodges says. "You can't see down through your floorboards, so it is usually a place that is out of sight, out of mind."
Excessive moisture is particularly prevalent in the late spring and summer, when hot, humid air enters through crawl space vents and collides with the cool air ducts and air-conditioned floors to form condensation, Hodges says. "With the climate we live in, vents simply don't work very well," he says.
For decades, Hodges says building codes required vents in crawl spaces, based on the belief the air circulation would keep them dry. However, studies such as one done by Raleigh-based Advanced Energy have now found that may not be true for humid regions. Advanced Energy studied 12 nearly identical homes in North Carolina to test vented and sealed crawl spaces. The 2005 study found that sealed crawl spaces saved, on average, more than 15 percent on annual heating and cooling bills, and they stayed substantially drier than the wall-vented crawl spaces during humid seasons.
Dry-Pro owner Ron Weatherly says an encapsulated or sealed crawl space has a vapor barrier on top of the dirt. It starts with fully drying out the space, blocking the vents, and adding a drainage system to funnel away water and a dehumidifier to dry the air.
Sealing a crawl space costs on average of about $5,500, Weatherly says. "It could range from $1,500 to $15,000-plus — it just depends what's going on," he says. There's no license required for basement waterproofing, so Weatherly suggests asking for references and checking reviews to avoid companies that improperly install cheap vapor barriers or recommend more work than necessary.
"If you don't go in your crawl space, have someone in the industry look at it to make sure everything's OK," Weatherly says. "Some older houses are absolutely fine, and some new ones are damaged. It comes down to what's going on with the whole house."