Replies

1. 
   Guest_ | Mar 04, 1999 12:30am | #1

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   BTI. Why do you need to add additional foundationn vents? The best way to do damage to the house framing is by adding more foundation vents. If the outside air is 90 degrees F and 90 percent relative humidity and you bring in the hot humid air inot a crawl space that is at 50 degrees F. you'll get condensation,mold and fungi and start the rotting of the framing.

   The two most important things to do is to (1) make certain the ground around the exterior of the crawl space is sloped away from the foundation so that rain water drains away from the crawl space. Make certin that down spouts are well away from the foundation. Keep all shrubbry, flower beds and what have you two feet away from the foundation.

   On the interior crawl space cover the dirt floor with a 6 mil vapor diffusion retarder (VDR)--what you call the vapor barrier--and run it up the inside of the foundation walls about a foot or more. Attach it to the foundation walls with 1x3 preservative treated lumber.

   Now close any existing vents and forget adding more vents. GeneL.

2. 
   Gene_B. | Mar 04, 1999 04:24am | #2

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   Gene L., your advice is on target up until that last line. I live in semi-arid west Texas and the Building Inspector here would insist on venting of crawl spaces in accordance with UBC. I believe that UBC requires venting area equal to one sq.ft. for each 150 sq.ft. of crawl space area, but the Building Official may reduce that to 10% of that area if a vapor barrier is applied as you suggest, and there are no severe groundwater or other moisture problems. BTI should verify that the Building Official in his area holds to that.

   I would like your thoughts on this.

   By the way, spread that advice around on keeping shrubs and flower beds away from the foundation. Homeowners and Landscapers love the look, but take it from an architect with some years in institutional facilities management and in renovation of older houses in spare time, they are a major source of many of the problems we have with structures, termites, moisture, etc.

   Thanks for your time.

1. 
   wildwill_ | Mar 04, 1999 07:02am | #3

   *GENE,WHAT'S THE BEST VDR MATERAL TO USE IN A CRAWL SPACE. MY MOTHER-IN-LAW JUST BOUGHT A HOUSE WITH A CRAWL SPACE AND NO VDR INSTALLED. I"VE SEEN POLY DEGRADE AND BECOME BRITTLE. THE #@$$!! THAT INSTALLED THE DRYER VENT STUB IT INTO THE CRAWL SPACE, ALL THE MOSTURE CONDENCED ON EVERYTHING, WET FG, TRUSSES,BLOCK. ALL THE VENTS DID KEEP IT COLD , HEAT WENT OUT MOSTURE STAYED IN.

1. 
   josh | Mar 04, 1999 08:19am | #4

   *We all know conditions and codes can vary around the country. Here in the northwest it can be very wet year round.We used to make our "bread money" by fixing rotted out floors etc and mostly caused by people blocking off the vents year round. I can understand closing off the vents when temps are down but they have to get opened up when they can.Luckily (?) now we pass that work on to younger more agile kids to crawl under houses and jack them up and replace rotted joists. Vapor barriers are a major major help in prevention of problems and rarely are we called out if a vapor barrier is present unless the foundation drianage is not working or a high watertable is causing the crawl space to act as a "pool" and the moisture gets around and through the vapor barrier.

3. 
   BTIggyaol.com | Mar 04, 1999 08:19am | #5

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   I live in the south where we only have crawlspaces instead of cellers or
   basements I need to add additional vents to the foundation the house is made
   of brick .Would i do any structual damage to the house by knocking out several
   bricks to add standard store bought vents