recently had a presentation by a crawl space contractor---he stated that when they are called in to restore a wet crawl space and put a vapor barrier in they seal all crawl space vents--he said they all should be sealed and HI should recommend that

now i was always told that the juror was still out on this---open vents in summer--close in winter--what does everyone think--and what if crawl has heat/ac vent
charlie

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RR-0401: Conditioned Crawl Space Construction, Performance and Codes —

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Dave

Here in northern Nevada the argumant is always whether or not to open or close the vents. Most get closed and stay that way forever or until an HI or pest guy comes along.

I usually tell them to open the vents always to allow for ventilation. Many of our crawlspaces are damp.

Recently a company in Carson City has been selling the "Clean Space Crawlspace System". This system does require closing and sealing of all the vents as well as any other gaps or holes to the exterior. A heavy guage vinyl moisture barrier is installed and sealed at the seams and to the perimeter foundation wall. A sump pump with battery back-up is installed as is an automatic fan system. I hear its really spendy to install.

I've only seen one in the Reno area and it was a pleasure to crawl around in - really clean. The home above was a disaster but thats another tale.

Jonathan

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Jonathan M. Cartwright
Newberry Inspections, LLC

jonathan
clean space is who gave our presentation
thanks

Beware of seminars or presentations given by persons or companies pushing their products or services.

Most are professional salespersons and could sell you tits off a bulldog and make you think you needed them. And got them for a good deal.

rick

rick

i know the sales pitch stuff--does texas have crawl spaces and what do you tell your client---open close--stuffed---what--that is what i'm asking for--country wide
thanks
charlie

Charlie,

In my 20+ years of crawling foundations, I could count on my hand the number of homes I've seen with a vapor barrier.

Those that did have them were not installed properly. Large puddles of water is seen on top of the vapor barriers that I've seen or pictures of.

Here in our area, most HI's recommend leaving the foundation vents off all year to allow ventilation of the crawlspace.

I've seen many homes that were soaking wet and condensation dripping off the floor joists due to having no ventilation. You take the vents off, place a fan under the house and the crawlspace would dry out in just a couple of days.

We used to do this all the time doing termite treatments. Some houses would have water ponding along the inside walls of the foundation. Most were due to improper drainage. Regardless, we could not termite treat or inject chemical into standing water so we had to take measures to get the soil dried out. AIR MOVEMENT worked great with any moisture problem.

There is some homes I've seen that actually had some type of fan system that was designed to fit in the foundation vent opening to push the air. We used to see them advertised in a PC magazine all the time. Some PC companies installed them in the slow times of the year.

Rick

Here is North Carolina we have 90% humidity with 90 degree heat in the summer. The crawl space area is cool. Guess what happens. The humid air goes into the cool crawl space and condenses. The air circulation attempts to dry the space out but the air is so humid, it is difficult for it to absorb more.

The best idea is to close the crawlspace, insulate the walls, vapor barrier on floor and walls, and condition the space.

Most of the homes around here have 75%-95% of the crawl space floor covered with vapor barrier. New construction is approaching 100% coverage.

If the client is not going to close and condition the space, then ventilate. At least some of the moisture will evaporate.

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Bruce Ramsey
Advocate Inspections
www.NCAdvocate.com

In the South I would advise folks to open the crawl space vents.

A sealed crawlspace is only good if it was designed to be sealed. I have seen numerous problems with crawl spaces that have been sealed and they were not originally built to be sealed.

If the ground is prone to being damp, then you don't want to seal that moisture in.

As for vapor barriers, the IRC requires them so I would hope that all new construction has one.

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Scott Patterson
Spring Hill, TN
http://www.traceinspections.com

Uncle Joe Lsitburek has some good advice on the topic.

http://www.buildingscienceconsulting...s_moisture.pdf

I like his Top Ten Lists

Building Science Corporation - Joe's Top Ten List of Dumb Things to do in the South

Building Science Corporation - Joe's Top Ten List of Dumb Things to do in the North

Obviously, he's more passionate about the South!

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Erby Crofutt, Georgetown, KY
B4U Close Home Inspections & Radon Testing
www.b4uclose.com www.kentuckyradon.com