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Old 07-28-2011, 10:53 AM   #1
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spacing between rim joist vents

A low income weatherization program put floor insulation in my dad's house. After the fact I was informed we now needed more vents. I know the fomula and I come up with 4 and they say 7. The current vents are about 6-7 feet apart, house built 1953. Because of the floor joist, the vents will not be centered. With that some of the vents will be about 20 inches; apart. Will that spaceing compromise floor or house structure. If any thing I would allow 3-4 but not 7. The way the house is, because of addition, the venis would all be aded to two sides of the house. I am not interested in a vapor barrier. We live in mild weather in san jose CA I crawled under the house on a 98 degree day and the dirt was cold but dry and no moisture on baords. Not much rain in winter. If I would have had this information before hand I would not have allowed them to put the insulaiotn in the floor. Some advise just leave as is. Thank you Jude.

Last edited by jude morrison; 07-28-2011 at 11:02 AM. Reason: something different showed up in message
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Old 07-28-2011, 11:24 AM   #2
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By the CRC you need 1 sq. ft. for every 150 sq. ft. of crawl space.

But since you are not experiencing any moisture problems under there I would suggest putting in a few more vents as the new insulation might act as a bit of a vapor barrier not allowing the new moisture to escape as it may have done before having the insulation.

You are probably not required to pull a permit for the new insulation so you would not be subject to inspection by you B.D. In any case they would probably not require bringing the venting up to code. (possibly, not guaranteed)

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