Wet Crawl Spaces Make For Wet Houses - A Follow Up

By
Home Inspector with Jay Markanich Real Estate Inspections, LLC 3380-000723
https://activerain.com/droplet/4tyc

Wet crawl spaces make for wet houses - a follow up.

My previous post about wet crawl spaces and wet houses spurred me to do additional research.

When I have HVAC or ventilation questions, I contact Dr. Max Sherman.  His team at the Lawrence Berkeley Labs is integrally involved with ASHRAE and RESNET/HERS energy standards.  Familiar with him for decades, I have an engineering book in my library he wrote years ago!  Dr. Sherman has always been exceptionally generous with his time and has always answered my questions.

I wrote him about the confusing info out there about ventilation - summer vs. winter, hot weather vs. cold weather, forced air movement vs. passive air movement, etc.  And I discussed the very wet crawl space yesterday, sending some photos.

The terrifically wet crawl space in question was intended to be ventilated.  But the vents had been closed, perhaps for some time.  There are "vent less" crawl spaces created now, but those have particular criteria as regards materials and techniques.  So my questions concerned ventilated crawl spaces in general.

One specific in my email was this:  "My philosophy is that dead air is not good air."

The first line of his response:  "Either a  vented or sealed crawlspace can work.  One must look at heat, air and moisture transport and make sure the design is sufficient whatever the choice."

The 2009 International Residency Code states this as regards crawl space ventilation:  "R408.1 Ventilation. The under-floor space between the bottom of the floor joists and the earth under any building (except space occupied by a basement) shall have ventilation openings through foundation walls or exterior walls. The minimum net area of ventilation openings shall not be less than 1 square foot (0.0929 m2) for each 150 square feet (14 m2) of under-floor space area, unless the ground surface is covered by a Class 1 vapor retarder material. When a Class 1 vapor retarder material is used, the minimum net area of ventilation openings shall not be less than 1 square foot (0.0929 m2) for each 1,500 square feet (140 m2) of under-floor space area. One such ventilating opening shall be within 3 feet (914 mm) of each corner of the building."

The National Association of Insulation Manufacturers (NAIMA) defines a Class 1 Vapor Retarder as:   Class I - Very low permeability vapor retarders - rated at 0.1 perms or less. Sheet polyethylene (visqueen) or unperforated aluminum foil (FSK) are Class I vapor retarders.  

 

To be effective, this vapor retarder, a thick sheet of plastic, must cover the entirety of the soil, be sealed together and go all the way to the edge of the foundation wall.

Dr. Sherman further:  "If the crawlspace is isolated from the main space (i.e. by good thermal, moisture and air barriers) then the question is only about keeping the crawlspace from having moisture problems. (A crawlspace that has leaky ducts going through it can never be isolated from the main space.)" 

This crawl space did not have good moisture barriers, and as the vents were closed off there was no way to carry off moisture.

In 2000, Clemson University studied ventilation in what they call "Clear Vent Areas (CVA)," meaning attics and crawl spaces, and concluded with what became the IRC standard for crawl space ventilation which came later - one square foot of venting is needed for every 1500 square feet of soil area.  And, further, the obvious - that the soil needs vapor retardation.  Another reason the Clemson study says venting is needed is to carry off gases from termite treatments, pressure-treated wood and radon.

The house, of course, needs to be separated with vapor retardation from this moisture also.  Dr. Sherman addresses that above in that the "crawlspace is isolated from the main space ... by good moisture and air barriers."  And he concludes to me:  "If there is proper venting, and moisture control, then a vented crawlspace can work fine."

So, as he stated - heat and moisture need to be transported, moisture has to be retarded and controlled, and the house has to be isolated from the moist crawl space.  

The mistakes in this house included not having proper soil vapor retarded and then closing off the vents to prevent air movement.  And the results are hideous.

My recommendation:  information on the Internet can be confusing!  Name your topic - medicine, history, sports, ventilation, or whatever - and you can probably find competing philosophies.  But common sense should be good sense.  Moving air transports moisture and gases.  And moving air is beneficial when a space is not intended  to be sealed.   And this crawl space was NOT intended to be sealed!

 

 

 

 

Posted by

Jay Markanich Real Estate Inspections, LLC  

Based in Bristow, serving all of Northern Virginia.

Office (703) 330-6388   Cell (703) 585-7560

www.jaymarinspect.com


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Rainmaker
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James Dray
Fathom Realty - Rogers, AR
Exceptional Agents, Outstanding Results

I have walked into the basements and found in some homes as you indicated they have closed off the vents and it shows.  Good post Jay

Aug 14, 2014 09:12 PM #1
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Lenn Harley
Lenn Harley, Homefinders.com, MD & VA Homes and Real Estate - Leesburg, VA
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GEEZ!  You didn't warn me that I'd have to consider construction matters, said the new home owner to the real estate agent.

This article is very helpful info IF a house has a crawl space foundation.  That's a big IF in an area where so many homes have a basement foundation.

No matter, the moisture matter is usually far above the pay grade of the average home owner.

 

Aug 14, 2014 09:19 PM #2
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TeamCHI - Complete Home Inspections, Inc.
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Good morning Jay. I see a lot of problems with moisture and moisture barriers on older properties. These conditions often lead to microbial activity.

Aug 14, 2014 10:09 PM #3
Rainmaker
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Sandy Padula and Norm Padula, JD, GRI
HomeSmart Realty West & Geneva Financial, Llc. - Carlsbad, CA
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Jay: Great you followed up with additional information. In this case that you encountered; before the action you mention in this follow-up can be taken, there should be extensive remediation and preparation taken to insure a successful fix.

Aug 14, 2014 11:44 PM #4
Rainmaker
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Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

James - sometimes basements do get really moist and you can smell it.

Lenn - I just did a pre-drywall this morning in Clifton with a huge house that is 1/2 crawl space!

Michael - that it does!  I didn't go poking around for the moldy spots, but sure smelled stuff in the main house!

Norman - remediation in this house would be extensive.  This problem has gotten worse for a while.

Aug 15, 2014 12:42 AM #5
Rainmaker
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Than Maynard
Coldwell Banker Heart of Oklahoma - Purcell, OK
Broker - Licensed to List & Sell - 405-990-8862

But, if I close off the vents that makes my house more energy effiecent and saves me money, right? I mean who wants all that air flowing under the house and up through the floors?

Homeownership is NOT for everyone no matter what people think.

Aug 15, 2014 02:33 AM #6
Rainmaker
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Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

It might not be Than!  Hopefully there is a modicum of insulation so air does not flow, um, everywhere...

Aug 15, 2014 09:15 AM #7
Rainmaker
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Lisa Von Domek
Lisa Von Domek Team - Dallas, TX
....Experience Isn't Expensive.... It's Priceless!

Hello Jay,

So basically, moisture is not your friend in a crawlspace or basement...as you said, common sense - a commodity that seems to be MIA these days. 

Aug 15, 2014 12:10 PM #8
Rainmaker
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Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Closing a crawl space like this is the opposite of the guy who removed insulation from his attic on my post the other day Lisa.  Both are set ups for problems.

I like the new avatar! 

Aug 15, 2014 09:17 PM #9
Rainmaker
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James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

Jay, If that photo is of the crawl space you have been writing about, well obviously the moisture issue is not to due with the vents, but ground water. I had a space similar yesterday. The ventilation was not even discussed with my clients. Mine was a drainage issue. 

Aug 16, 2014 10:40 PM #10
Rainmaker
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Tom Arstingstall, General Contractor, Dry Rot, Water Damage Sacramento, El Dorado County - (916) 765-5366
Dry Rot and Water Damage www.tromlerconstruction.com Mobile - 916-765-5366 - Placerville, CA
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Jay - Moisture under a home can be troublesome and the correct answer is important. You have done a lot of research in coming up with the answer.

Aug 17, 2014 12:27 AM #11
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Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
Seattle Home Inspector

Jay, me thinks that is a water issue, not a ventilation issue.  With that much water in the crawl space it would mask any issue with the ventilation.

Aug 17, 2014 01:32 AM #12
Rainmaker
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Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Jim - it is the same crawl space.  I think ground water is a problem!  But it is not controlled.  And the sub floor area is not controlled.  I have had wet crawls all summer long, with proper venting, but never such dripping.  Often I squish around on top of the mud, but am protected by the plastic.  Many exposed areas of soil here though!  And there is nothing here, as Dr. S says, to "transport" the moisture exuding into the air.

Tom - Dr. Sherman is very generous with me.  I have contacted him many times.   He nails it every time.

Charlie - it is a water issue!  In the ground and in the air!  And not controlled.  I see wet crawls all the time without this dripping.  My very sophisticated (okay, it's a home model so not THAT sophisticated!!) home weather station said it was 80F with 45% humidity that day.  So it was not that wet outside.

Aug 17, 2014 02:01 AM #13
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Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
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And with that kind of humdity in the summer I can see where you might want to close the vents in the summer and open them in the winter---but only if there are no ground water issues.  At that humidity and temperature in the summer humidity levels in the crawl space could get VERY high---raining high, especially in conjunction with an already wet crawl space.

Aug 17, 2014 03:35 AM #14
Rainmaker
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Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Sí, mi hermano.  If you look around the internet you find credible sites that say close summer, open winter and others that say close winter, open summer.

That was one of the very questions I posed to Dr. Sherman.  My quotes in the post are exactly from him, I just divided up his comments in the post. 

My feeling is dead air is bad air.  Especially when so wet!

You have to understand, around here, in summer, 45% humidity is not that high.  It's 87 and sunny here today and my station says 66% humidity.  I remember pitching in baseball games when the humidity exceeded the temperature and I would lose 10 pounds!

I think the vents here had been closed for a long time.  See the photo of the center beam in the previous post - looks real wet for a while.

The whole time in the crawl I thought I heard music.  I think it was from Butch Cassidy and the Sundance Kid - "Rain Drops Keep Falling On My Head..."

Aug 17, 2014 05:31 AM #15
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Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
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I know Jay, but as soon as you bring that 66% humid air into a space that is 55 degrees and 50% humidity it will not say 50% very long---it will rain.  If it is 50 degrees and 85% humidity then it will typhoon--just like your pictures.  The whole back-and-forth over closing and not closing the vents is regional.  Here they must stay open year round.  Crawl spaces around here have their highest humidity in the summer and go down in the winter even though the outdoor humidity is near 100% much of the time.  It is all about temperature differentials and how much moisture air can hold at different temperatures.  Venting cannot fix ground water issues in crawl spaces---in some climates improving ventilation can actually make it worse.

Aug 17, 2014 09:19 AM #16
Rainmaker
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Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

No, venting cannot fix ground water issues Charlie!  For the vent less crawls to work you have to have certain materials and techniques in place.  This crawl had none of that.  Dr. Sherman's word "transport" for the air is relevant here I think.

Had that crawl been a comfy 55F I would have taken my union nap!  That mud was soft under me!  Conforming!  Just squiggle in there and start snoring!

Aug 17, 2014 10:14 AM #17
Rainmaker
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James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

I think we are talking about apples and oranges (fruit salad anyone). Like Charlie said, you can not possibly know if a ventilation issue exist with that much water in the crawl. What you see would be expected under those circumstances. 

I hear they get big bucks for mud baths at the spa. I have never heard of the mud nap. A new product? 

Aug 17, 2014 10:11 PM #18
Rainmaker
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Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

That's what I said to you earlier Jim!  I have seen many crawls with this much ground water, but this is my first this summer with the vents closed (and apparently closed for a long while).  The moisture has no choice but to collect as there is no "transport."

I used to have a water bed which was uncommonly comfortable!  Maybe stumbling across the new Mudbed would be marketable?  Gotta tell you, mud is every bit as good as the foamy "conforming" mattresses!

Aug 17, 2014 10:16 PM #19
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