Why is my ductwork sweating in the crawlspace and what should I do about it?
This is an all too common question during this hot humid weather. For many years we all thought we should ventilate the crawlspace more, even adding fans to draw outside air in. Building codes have reinforced the ventilation theory with new construction homes over the years. What scientists have now taught us is that we are making the problem worse. Outdoor air in times of average to high summer humidity holds much more water vapor than our crawlspaces. Bringing in that air to the crawl just brings in more moisture. This moisture then condenses on cold surfaces, much like the beads of sweat on a glass of ice water. Usually the first surface to sweat is the ductwork. Continued high moisture levels can allow condensation on wood surfaces, floor insulation, plumbing pipes and more. When you consider that this can happen for almost half the year, wood rot, mold and other nasty consequences are, many times, the result. Festering crawlspaces was a description heard recently and it really fits. The pictures below came from a area crawlspace at the end of last summer.
What do we do about it? First and foremost, make sure you eliminate any source of outside water into the foundation. Then you can try closing the crawlspace vents and certainly, shut off any crawlspace exhaust fans. Run these when cool weather arrives to dry out the space. You can temporarily operate a small dehumidifier inside the space with the vents closed, too. But the best long term solution is a closed crawlspace. Studies have shown that humidity levels remain lower in a closed crawl and utility bills are reduced too. Note that it is extremely important to execute a closed crawlspace properly. Doing it wrong can be much worse. Contact us if you would like more information about closed crawl spaces.
