If you think closing off crawlspace vents is saving you money, you're all wet!

By
Home Inspector with Sherlock Home Inspections

    In today's economy, many people have become energy conscious.  In order to save on those monthly energy bills, homeowners have come up with some creative ways to seal off their homes from the elements.  Unfortunately, some of the common methods being employed are actually detrimental to the health of the home, and do little to accomplish the desired end.  One of those methods is closing off or covering the crawlspace vents in the curtain wall.

     It seems to make sense.  Here in the south, insulation is rarely installed under the floor of a home with a conventional foundation.  Our warm climate does not dictate the necessity.  But in the winter, the idea of cold air circulating under your house makes you shiver, and that first winter energy bill makes you shudder!  So, you reasonably figure that closing off those "pneumonia holes" all around the house will keep some of the warm air in, and the cold air out.  Right?  WRONG!

    Closing off crawlspace venting does little for your bottom line on heating or cooling bills, and may have serious repurcussions as well.  The purpose of all those holes in the side of your home is to allow air flow.  The purpose of having air flow in your crawlspace is to prevent the accumulation of water vapor.  The purpose of preventing this accumulation, in turn, is to prevent actual structural damage, discourage the growth of molds which may be detrimental to your health (especially small children!), and to encourage wood destroying insects to look elsewhere to establish a colony.

    "Oh, come on!" you say.  Surely a little water vapor can't do all that!!  After all, we live in a humid climate here in the South.  Humidity is everywhere.  Yes, that is true, but here is what happens:  When you close off those vents, you trap whatever moisture is already in the air under your home.  The humidity is increased every time it rains, especially if the drainage around your foundation is inadequate in areas.  Eventually, the floor joists and girders, even the masonry piers under your home become saturated with moisture.  Molds love the combination of wood and water.  The damp, cool soil is an invitation to termites.

    I have learned over time to put on my high-tech filter mask when entering a crawlspace that has been sealed off in such a manner.  Why?  Mold.  Depending on how long venting has been compromised, I expect to find joists and girders that are damp or even wet to the touch, with molds and fungi visible on the surface.  I don't want to breath in spores that can make me sick!  In addition to that, joists can become bowed, weakening the home's strutural integrity.  Think about this.  When a craftsman want to curve a piece of wood, what does he do?  If you've ever re-caned an old chair, what do you do with the caning material to make it pliable?  That's right you soak it!  That is exactly what happens when you trap water vapor under your home!  The process is much slower than immersion, of course, but the end result is the same.  You create weakened wood structural members that are slowly bowing and rotting.  Your kids start to have respiratory problems, and you don't know why.  Eventually, shoring up floors with extra piers and girders, or having to get rid of mold becomes an expensive proposition.  Suddenly, a few (and I do mean a few) saved bucks on an energy bill looks like a bargain.

    So get out there and yank off those neatly cut plywood planks you stuck over those holes four years ago!  If you don't have it already, make sure there is a plastic vapor barrier covering the ground under your crawlspace.  Check out your drainage around the foundation, and make sure that roof drainage and surface water is moving as quickly as possible away from your foundation.  You can pat yourself on the back when you don't have to take out a second mortgage to fix a terrible mistake.

    For more cool information for homeowners and real estate professionals, visit www.sherlockhomeinspects.com

close

This entry hasn't been re-blogged:

Re-Blogged By Re-Blogged At
Groups:
Ask the Home Inspector
Property Inspection Discussion
Tags:
mold
moisture
structural
drainage

Post a Comment
Spam prevention
Spam prevention
Show All Comments
Rainer
17,055
Jimmy Breazeale
Sherlock Home Inspections - Coldwater, MS
Thanks to everyone who has contributed their knowledge to this thread.  Special thanks to D.J. for your contribution.  This is the way to have a discussion, where civility rules.  Now: Somebody come back with some thoughts on what we may recommend in a case where a home has no central air or heat, is unlikely to get that upgrade in the near future, and has a crawlspace moisture problem.  Venting with vapor barrier and a continuous duty fan?  And maybe adding floor insulation?
May 13, 2007 09:30 PM #36
Rainmaker
74,451
Bob Elliott
Elliott Home Inspection - Chicago, IL
Chicago Property Inspection

I am personaly beginning if The wrong forum was clicked on,and somehow I ended up chatting with a group of scientists.

Damn you guys are good.

May 14, 2007 12:15 AM #37
Rainer
5,911
Donald Sutherland
Marathon Constructors Inspection Services - Seward, AK
Inspector-Seward, Alaska

Everbody,

This has been an excellent debate. I think we all won. Regional differences make the requirements important. Nowdays energy efficiency is of key importance. Tightening up houses, new construction is key to efficiency, but creates other challenges. Indoor air quality is at risk, proper ventilation and moisture control are of prime importance. So, you have to do what you have to do.

Alaska Don

May 15, 2007 01:06 AM #38
Rainer
67,262
David Helm
Helm Home Inspections - Bellingham, WA
Bellingham, Wa. Licensed Home Insp
Looks like my name got cut off on my previous post.   The one about home inspectors agreeing is the one.  I never like to do anonymous posts on any board.  Benjamin, I have had clients follow me around in crawl spaces.  You should try it some time.  It can be an education and will give you a oneup on other mortgage brokers!
May 18, 2007 06:49 PM #40
Rainer
17,055
Jimmy Breazeale
Sherlock Home Inspections - Coldwater, MS
What??!!?? Home Inspectors agreeing?  LOL!! David, only to a certain degree!  I think we did pretty good with this one, though!
May 18, 2007 08:41 PM #41
Rainer
26,007
Glenda Crowell
John L. Scott, Bend - Bend, OR

Jimmy ~ we live in Bend. Dry with warm summers and cold winters. The sand tends to wick the moisture away.

 

G.

Jun 13, 2007 11:42 PM #42
Rainer
17,055
Jimmy Breazeale
Sherlock Home Inspections - Coldwater, MS

Glenda,

I'm not sure where Bend is, but it sounds like you have a climate with very low relative humidity.  I wouldn't be surprised if there are not a lot of homes in your area with louvered vents that can be opened and closed at will.  What I should have done, in my original post, was make it clearer the specific climate type and home type I had in mind, though I thought I had done that.  As it is, I inadvertently invited comments contrary to my advice.  And it was a good discussion.  Lots of good presentations and advice from all corners.

Jun 14, 2007 01:13 AM #43
Rainer
9,369
jamie allen
Allen's Pest Inspections - Evansville, IN
Jimmy, i think that you have hit on a good topic to talk about. What i have learned from "Crawl Space Science",  hands on problem solving & on going inspections is that having vents on a home is really BAD in most climates. Ideally, having air flow across the earth to help keep it dry makes perfect since. The truth is that having foundation vents does the opposite of what they we're designed to do. No matter what time of year hot or cold the air flowing into the crawl space is mixing with the conditioning of the homes heating & air condition. When hot & cold air mix it changes the relative humidity & that turns into rain or in a crawl space you get condensation on everything within the crawl. Basicly, by having vents on a home will cause more rot, mold & termite problems. Here is another link source to do some reserch with.  www.basementsystems.com Sincerely,
Jun 19, 2007 12:47 AM #44
Rainer
26,007
Glenda Crowell
John L. Scott, Bend - Bend, OR

Yes Jimmy we do have the louvered vents and most only work the first couple of years and then off to purchase plugs. *Removing the plugs in warmer months is very important.

 G.

Jun 20, 2007 12:39 PM #45
Rainmaker
206,029
Erby Crofutt
B4 U Close Home Inspections&Radon Testing (www.b4uclose.com) - Lexington, KY
The Central Kentucky Home Inspector, Lexington KY

Well, I can't contribute more than is already said above, but did have this recent experience (???) to share visual examples.

30 plus year old house
no vapor barrier
no vents
poor drainage
BIG PROBLEMS!

kentucky home inspector mold joists crawl space

Moldy Joists

 

kentucky home inspector rotted joists

Sagging girder/beam

kentucky home inspector rotted joists & termites

Rotted rim joist, termites, mold

kentucky home inspector see the wet crawl space

Wet valley.  See the peak at bottom right.  Leakage from waste pipe above.

kentucky home inspector mold in crawl space joists

More mold, rot, and termites

kentucky home inspector mold joists termites

More rot & mold.

Enjjoy!

 

Jul 12, 2007 03:31 PM #46
Anonymous
Anonymous
WOW! Looks like the one I did last April. The only thing missing is the "high tide" water stain marks on the foundation walls from when the water pours in from the vent wells!
Jul 12, 2007 04:25 PM #47
Anonymous
Bruce Pinel
oops, forgot to sign it.
Jul 12, 2007 04:27 PM #48
Rainer
67,262
David Helm
Helm Home Inspections - Bellingham, WA
Bellingham, Wa. Licensed Home Insp
Erby, those are the best proof of the need for proper crawlspace management, whether it be conditioned space or proper venting.
Jul 12, 2007 06:28 PM #49
Rainmaker
74,451
Bob Elliott
Elliott Home Inspection - Chicago, IL
Chicago Property Inspection
Erby,I would love to see a few closeups of the termites if you have them.
Jul 12, 2007 07:22 PM #50
Rainmaker
206,029
Erby Crofutt
B4 U Close Home Inspections&Radon Testing (www.b4uclose.com) - Lexington, KY
The Central Kentucky Home Inspector, Lexington KY

Only a couple.  I don't spend much time on bugs.

 

Kentucky Home Inspector Termites

Look at the wet spot!

Kentucky Home Inspector termites 

If you're going to use macro, put your camera straight on to the wall instead of an angle.  Mine focused just a little to the right of the termites so they are kind of fuzzy on the left edge of the focused area.

Jul 13, 2007 08:20 PM #51
Rainer
17,055
Jimmy Breazeale
Sherlock Home Inspections - Coldwater, MS

Thanks for the pics and the input, Erby.  I just inspected another one of those Mississippi Delta homes with crawlspace over gumbo mud soil today.  For those who aren't familiar with the particular soil condition, it's a smorgasborg of everything that has washed down the Big River for millennia.  Silt, loess soil, dark clays, making up a topsoil 12-20 feet thick.  Highly permeable, it soaks up water like a sponge and releases it as steam on a hot summer day!  A vapor barrier is an absolute must for homes in that area, and I've yet to see one over there without one---and yet, because of the particular qualities of the soil, you can still have a moisture problem big-time if you don't keep it vented.  Bear in mind that the Delta is still a very economically depressed area.  Many, many homes don't have central air, and homeowners can't afford the installation of that, much less creating a sealed crawl space.  One solution that seems to be unique to the area is installing a continuous duty fan in the access door, and switching it from a location inside.  This way, during rainy periods, they can be switched off to avoid pulling in saturated air.  Relative humidity is still a problem most of the rest of the time here, but keeping the air moving does a pretty good job.

BTW----This has absolutely nothing to do with crawlspaces, but has anyone noticed that, when you use spellcheck here, it always calls it to your attention when you fail to capitalize "realtor"?  Apparently, it's ok not to capitalize "home inspector."  Does this tell us something?  :-)

Jul 14, 2007 12:56 AM #52
Rainmaker
206,029
Erby Crofutt
B4 U Close Home Inspections&Radon Testing (www.b4uclose.com) - Lexington, KY
The Central Kentucky Home Inspector, Lexington KY

Yes, it tells me Realtor is trade marked / registered (whatever) and Home Inspector is not!

 Bet you're enjoying this steamy weather??

Jul 15, 2007 03:53 AM #53
Rainer
639,033
Carl Winters
Canyon Lake, TX
Thanks for the good reading and information. Never know what we are going to find when we go into a crawlspace. I haven't seen any yet that have been closed but may if electric bills continue to rise.
Jul 15, 2007 09:48 PM #54
Rainer
639,033
Carl Winters
Canyon Lake, TX

Hello there Jimmy

How are things going there in Coldwater? Here's to you having a good new year.

C&C

Dec 29, 2010 12:55 PM #55
Rainer
639,033
Carl Winters
Canyon Lake, TX

Hi Jimmy

Wanted to stop back by to say, that we hope you have a safe and Happy New Year's weekend.

C&C

Dec 30, 2010 01:40 AM #56
Post a Comment
Spam prevention
Show All Comments
Rainer
17,055

Jimmy Breazeale

Ask me a question
*
*
*
Spam prevention

Additional Information