I live in the humid Southeast near Raleigh, NC. In this region closed crawlspaces are becoming more common. The idea is to seal out moisture from the ground and simultaneously seal out humid outside air from infiltrating the crawl space, cooling off, and condensing.
However, once the sealing is done a mechanical means must be implemented to provide a drying mechanism for the crawlspace. This can be accomplished by either a controlled "leak" (outlet) from the supply side of the existing air handler or from a separate dehumidifier. The goal is to keep the humidity in the crawl space below the 70% where mold and mildew start to become a problem.
The crawlspace has been sealed and I have been monitoring the humidity levels with a remote monitor for the last several months. The humidity has been running between 65-78% using only existing leaks in the duct system.
The duct system and HVAC/ heat pump is only 2 years old and was well installed and mostly sealed. The main supply side leaks are at the pivot points of the 14 supply dampers. I was rather surprised to find Hart & Cooley didn't make a better sealed product! 28 of these holes adds up to a pretty large leak.
At any rate the humidity is running too high so am now faced with a decision. Should I add another humidistat controlled damper and outlet in the crawlspace to increase the "leak" or should I install a separate dehumidifier?
Do any of you have any experience with how well the extra damper can work in controlling the crawl space humidity? Granted this is all dependent on how much the A/C runs. This approach would probably be more efficient and less expensive than a separate dehumidifier.
Thanks for your thoughts, experiences, and ideas.