The story of the dampness in my crawlspace is a long and grisly one, but for purposes of this discussion I’ll try to keep it brief! The house was built about 15 years ago, down in a hollow, apparently with no site preparation, and the foundation was not coated. I thought I had addressed all of the necessary issues by having a well dug in the poured concrete floor for a sump pump, having a continuously running circulating system installed in the crawlspace with 2 vents each front and back of the house, and having all new insulation hung in early spring of 2006. I discovered last week that, with the humidity typical of mid-July in southeastern Pennsylvania, some of the insulation has fallen down completely and some is streaming down; the crawlspace now looks like Crystal Cave. I had planned to have someone install a simple but heavy duty dehumidifier as well, and guess I waited too long. My brother suggested a layer of Tyvek across the bottom of the insulation, and I’m interested in opinions as to the wisdom and viability of this plan. All other reasonable suggestions are welcome!
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Have you done any work on the outside? like maybe directing gutter/downspout water well away from the foundation? Regrading the area surrounding the house? Installed french drains to take the water away from the foundation?... etc, etc
"having a continuously running circulating system installed in the crawlspace with 2 vents each front and back of the house, and having all new insulation hung in early spring of 2006.
I discovered last week that, with the humidity typical of mid-July in southeastern Pennsylvania, some of the insulation has fallen down completely and some is streaming down; "
HIGH HUMIDITY levels are EXACTLY the reason that you won't want to have external vents that bring in moist air.
A crawlspace is naturally a cool space to start with. Then you air condition the house and it is cool enough for the air to condense.
The dewpoint in Philadelphia is now 72 degrees. So it is probably raining in your crawlspace right now.
What you need to do is converted this to a conditioned crawlspace.
Seal it off from the outside air. Insulate the WALLS and alow interior air to circulate.
A google on Conditioned Crawlspace and Sealed Crawlspace will get you more information.
Also http://www.buildingscience.com
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Check these links out, they've got some great info in them, not all of it will be applicable to your situation but a little knowledge goes a long ways. The second one is pretty large (2.82 MB) but it's worth reading.
http://www.1800arkansas.com/Energy/files/Clearinghouse/Closed%20Crawl%20Spaces_Quick%20Reference.pdf
http://www.1800arkansas.com/Energy/files/Clearinghouse/Closed%20Crawl%20Spaces.pdf
I live on an island so the dew-point is always pretty high (the air always carries a lot of moisture) so venting crawlspaces causes more problems than it solves because the moist outside air condenses on the cool surfaces in the crawl. I have taken to treating crawlspaces as "conditioned space", meaning that I install moisture barriers and insulation on the perimeter walls and the floor, a dehumidifier and if possible and I dump some heat from the household heating system into the crawl during the cold weather to help keep the dehumidifier working. I also remove the insulation in the floor system as it only seems to serve as a place for condensation to occur. We also work outside the foundation to move as much of the groudwater away from the building as possible by using gutters, downspouts and leader drains, proper grading and landscaping that is less dense and allows for some air circulation around the building.
I can tell you that, without exception, this has improved the conditions in the crawl and the living space above of every house we have done. There's been less mildew, mold and odor and it's generally improved the living conditions in the space above. And although I can't prove it I am certain that it also reduces deterioration of the building materials in the crawl. Yes, it does add a little to the energy bill but not one of my customers has complained.
This has been a bone of contention for quite a while and I'll bet that if you search the forum you'll find some other discussions here too.
Good Luck, Bill
In my experience, you can spend $10K applying an endless succession of bandaids in the interior and still be chasing your tail, or you can spend $10K to do the job right and fix the problem at the source -- exterior ground water diversion and control.
Mike Hennessy
Pittsburgh, PA
If does not matter how much work he does on ground water control if he is sucking HOT MOIST air into a COOL space. Instant rain..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"If does not matter how much work he does on ground water control if he is sucking HOT MOIST air into a COOL space. "
True enough, but if there was no ground water getting in, he wouldn't feel the need to suck in all that wet air to "dry the place out."
Mike HennessyPittsburgh, PA
having a continuously running circulating system installed in the crawlspace with 2 vents each front and back of the house
I am not sure exactly what this means--do you have an inline fan pulling air in and exhausting the crawlspace air? Sounds like a way to bring extra moisture in your house. I think you should close all of the vents except for where the fan exhausts and that will get the moisture down in the crawlspace and pull drier air from the conditioned part of your house. Also, you should insulate the crawlspace walls instead of the floor system.