condensation under crawl vapor barrier
You all helped so much on my last questions & this may be symptomatic of earlier questions on high humidity inside house back last summer.
had oversized HVAC-fixed that
turned attic exhaust fans off
Closed the crawl vents and sealed them. put off shelf dehumidifier in crawl and tidied up vapor barrier, and ran until humidity was less than 25% in crawl
Moisture on ducts and internal house humidity was resolved.
All was fine until under the house to get my snow shovel, yesterday temps in 20s here in Cent KY.
No signs of moisture penetration on block walls or on footer. But there is noticeably more condensation under vapor barrier on crawl floor. Will dehumid take that out or create more of a problem due to heat given off by dehumid and cause more condensation? Is the condensation under the VB a problem?
Should I unseal the vents and allow some air to move through (cold now and hot humid in summer)?
Replies
The condensation under the vapor barrier isn't a problem, so long as it doesn't get so bad that puddles develop. That's why the vapor barrier is there -- to keep the moisture in the soil, not the crawlspace.
The reason you did the VB was to keep that moisture under it.
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In addition to Dan and Piffin - long term, keep an eye on it. It is likely to slowly decreas over time (a vapor 'barrier' is really a vapor retarder) and the moisture in the soil will probably decrease over the years.
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What is under the VB? Looks to me the VB is doing its job - keeping moisture from entering the crawlspace. If it is soil that is under the VB I would not be concerned. If you don't like the "little bit" of moisture you can remove the VB and install 2" rigid foam, then re-install the VB
There is apprx 3 inches of gravel on top of bare soil, under the vapor barrier.
Should I unseal the vents and allow some air to move through (cold now and hot humid in summer)?
There are homes where the crawlspace is used as a heating plenum. The crawlspace is totally insulated and sealed. The furnace pumps hot air into the crawlspace and keeps the subfloor nicely warm, warm air enters the living spaces thru heatvents cut into the subfloor. These crawlspaces are absolutely dry - summer or winter
The barrier is working. Congratulations, Good Job.