I have a situation with an under vented crawlpspace . Due to
landscaping and architectual considerations, it will be almost
impossible to add more vents . I am interested in comments /
discussion on installing a basement dehumidifier or or exhaust fan
for supplement crawl space dehumidifcation .
I would seal the thing up unless you have water under there which should be
taken care of with perimeter drainage. This whole theory of having moist
summer air ventilate your crawlspace is slowly being dumped. All the warm
moist air does is condense in the crawlspace and make things worse. Like I
said, a wet crawlspace needs a perimeter french drain. But if it is
otherwise dry consider sealing it with foam walls and foam boards under the
If the crawl space isn't well-contained (like a basement), a dehumidifier
will never really conquer the moisture and it will run 24/7. You best bet
is good ventilation and a fan strong enough to move all the air through.
Wayne in Phoenix
If there's a nit to pick, some nitwit will pick it.
Is the moisture coming from the air or from the ground? In basements, it is
usually from the air---it hits the cold basement floor and deposits its
moisture. So if you ventilate and allow in more moist air, you get more
You have a crawlspace and I don't know what's happening there. If there is
water seeping into it from the ground, that's a different matter. But I
Not really. I have heard this argument many times, but it just does not
hold water. Well in some parts of the country that may be true, but in most
of the world it is not true. First, it is not moisture on the floor of the
craw space that is the problem, and that is the only part that may be cool.
The exposed structural members above the craw space are not likely to be
cool and yet it is they that get damaged if there is insufficient
ventilation to reduce the moisture level to that of the outside air.
Generally the ground is more moist than the air.
Many things are tried, but the only one that seems to work well is good
ventilation. Power vents may reduce the area requirements, but only if the
owner keeps the system going and they tend to not bother fixing things when
they go bad and then damage occurs.
If the floor is cool, that cools the whole room. More importantly, if there
is condensation on the floor, the air is in contact with water, and this
makes all the basement air very humid. The reason certain elements suffer
more damage is that they are more susceptible to damage.
Do you have plastic on the ground and good drainage around the basement.
Is humidity a problem, I mean you have measured it accurately. Every
house and area can be different in venting. A dehumidifier sounds like
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.