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Old 07-27-2008, 02:52 PM   #16
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dehumidifier INSTEAD of crawl space vents


Let's not shoot ourselves just yet.

Do you have a full basement adjacent to the crawl space? If so, the code allows you to provide ventilation openings from the crawlspace into the basement and omit the exterior vents.

If you're putting plumbing in this crawl space, you're crazy if you don't run HVAC to it, or at least open it up to heated basement space.

Would I accept operable windows/vents in the crawlspace as the means of ventilation? Nope, not if they're operable. You probably need to dump the idea of vents and look into conditioning that space somehow.

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Old 07-27-2008, 05:21 PM   #17
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ok, this is a mobile home with a large addition that i've attached a roof over the whole mess and squared it out which gave me a new dining room area 15x20. the front extends 6 ft beyond trailer, sides 3 ft. and rear 4 ft. all done on 6x6's with cement below all to code and passed, new trusses built offsite and shipped were used to do the new roof. i have the new dining room closed in so far with door and windows and i need to colse the crawl space off and continue on around the walls till i can tear out the trailer from the inside then install new joists and floors, walls, electric, plumbing, hvac, etc. fun, huh? it's been quite an undertaking all by myself with just the help of my kids and my wife when she's home and not working. i did have to tear out some small work i had done when this inspector came, but it was what he said that bothered me the most. " looks like i'm going to have to fight you on every nail you put in a board " .....so i'm here asking what you all probably see as stupid questions like simple electric i've forgotton or simply not used for years, but i cannot afford to spend money only to tear it out and redo it because i did not ask one silly question, so i hope you all can be patient with me...=o) this crawl space venting thing has me pulling out what's left of my hair.... i will try to load a pic so you all can see my nightmare... heh

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Old 07-27-2008, 05:32 PM   #18
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Old 07-27-2008, 05:47 PM   #19
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dehumidifier INSTEAD of crawl space vents


I'd really suggest talking to the inspector. Just because I say something's required or some other professional says they did this or that, it doesn't mean that it will pass. That is ultimately up to your inspector, so you should be consulting him with your concern of not wanting to install vents due to the plumbing present in the crawl space.
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Old 07-27-2008, 06:06 PM   #20
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dehumidifier INSTEAD of crawl space vents


if he ever returned my calls, maybe i could... the trailer has a crawl space too, and the inspectors told me it had to be SEALED when i mpoved in! then the inspector's areas changed, and now the new guy says this!
the pipe froze down there even WITH the insulation the GOVERNMENT WINTERIZATION PROGRAM put in and they sealed my whole crawl up TIGHT!!! until i went down there and wrapped the inlet pipe from the well in a 'special' way that keeps it unfrozen. but even THAT would not help if i have to keep the vents open all winter..... sooo, they WILL be closable, even if i have to retroclose after the final inspect. owell......
"if you do not ask, you will not know"
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Old 07-28-2008, 09:55 PM   #21
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dehumidifier INSTEAD of crawl space vents


Please take a look at www.BuildingScience.com publication RR0401 "Constructing Conditioned Crawl Spaces". It has the latest research (funded by your tax dollars) on this subject. The state crawl spaces should be attached to conditioned spaces & the only venting should be exhaust fans. With all due respect to building inspectors, who have caught many errors I have made, I find the best practices can be found by reading publications. I also designed residential heaters & dehumdifiers, which helps me sort out some of these humidity issues.
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Old 07-28-2008, 10:28 PM   #22
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dehumidifier INSTEAD of crawl space vents


Quote:
Originally Posted by PerpetuallyRepairing View Post
Please take a look at www.BuildingScience.com publication RR0401 "Constructing Conditioned Crawl Spaces". It has the latest research (funded by your tax dollars) on this subject. The state crawl spaces should be attached to conditioned spaces & the only venting should be exhaust fans. With all due respect to building inspectors, who have caught many errors I have made, I find the best practices can be found by reading publications. I also designed residential heaters & dehumdifiers, which helps me sort out some of these humidity issues.
I have read the site's articles, many times over, and compared them to the real world building situations. I am sure that KCT, and many other members here, in the building industry and community have read and studied the articles.
Like everything else, they are a researched "opinion" on "controlled studies", and theories...which in most cases, are relative to region and specific construction design. Everyone is welcome and entitled to their opinions, or their suggestions.

FWIW: Just because it is posted on a website, Does not constitute Building Doctrine, or even actual building science doctrine. BuildingScience.com is not the "bible" of the building industry. Evidently you accept it as such...and, to each his/her own, that is your right.

However, please do not quote one website's statements as the rules that should be governing all building premise, or even as, the basis for not following one's local (regional) building codes.

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Old 07-29-2008, 01:04 AM   #23
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dehumidifier INSTEAD of crawl space vents


What Atlantic says is very true, although there are informative articles on that site and the authors certainly seem knowledgeable. One must remember that there are only two authors/contributors at that site, so you're only getting the opinions of two people.

As stated on their site: There are two primary authors for the documents on buildingscience.com.

The building codes are written and adopted by panels of hundreds of people in many different specialties and in nearly every state and many countries around the world. I guarantee that the code-making panels do not always agree with more than a voting majority, and everyone on those panels are the top people in their respective industries. Therefore, based on the writing and the ICC's implementation processes, I put much more credibility in the codes than I do a website.

As with many construction-related topics, not everyone is going to agree on this. Therefore, I'd defer to what is required by the minimum standard of the code. Reading internet publications will do you no good when you're being turned down by the inspector for not meeting code with an internet-recommended installation that doesn't meet the minimum standard.

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Old 07-29-2008, 08:58 AM   #24
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dehumidifier INSTEAD of crawl space vents


not to get off topic here but what if i built in 5 crawlspace holes (5 vents required by code+math), made them 2x3' access doors, and then use soffit as skirting (they look almost the same) over the doors? that'd vent it more than enough to satisfy the inspector, yes? and the holed soffit would blend ok with the solid skirting so is this a possibility? i really need to finish this part of the house up here... heh.... tnkx

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Old 07-29-2008, 09:04 AM   #25
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dehumidifier INSTEAD of crawl space vents


also, the pipe from the well comes up through the crawl space cement, then spans 2 ft or so then into the house. when we bought this place i had to redo all the plumbing. copper all around down there was frozen and burst so i figured i'd move as much as i could into the house! LOL all my pipes EXCEPT the inlet are inside now but if i had to keep open vents all winter, it'd surely freeze constantly. if i custom build these doors, i can add an inside bracing for a foam/batt insert to seal the doors for the winter. my biggest concern is what the inspector will say?

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Old 07-29-2008, 09:23 AM   #26
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dehumidifier INSTEAD of crawl space vents


Per the IRC code, your vents' net opening (that's all of them combined) must be 144 square inches (12x12") per 150 square feet of floor space in the crawlspace. There mustbe a vent within 36" of each corner of the crawlspace, which promotes cross-ventilation.

As I've already said, all I can tell is is what the code says. Whether or not your inspector will allow operable openings is up to him, so he's the one to ask.

If your water supply line is a concern due to cold temps in winter, they do make electrically heated pipe wraps for this exact purpose. Kind of like a heating pad for water lines.
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Old 07-29-2008, 11:45 AM   #27
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dehumidifier INSTEAD of crawl space vents


soooo, i have 1100 sf of new addition, the old addition is block and sealed. 1100 div by 150 = 7.3.. or 8ft.? this is sq. ft. needed? so then if i went with just vent holes, i'd need 12x24" vents x 5 vent openings my architech recommended?
1440 sq." ?...man, i stink at math... does this seems to fit the bill? tnkx!
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Old 07-29-2008, 12:02 PM   #28
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dehumidifier INSTEAD of crawl space vents


Yup, 7.3sf of net vent area required by the basic code section, R408.2 of the 2003 IRC.

Sorry, I should have put this in my last post...Per section R408.2(exception 2), you can reduce that area to 1/1500 of the under floor square footage by installing a vapor barrier on the ground (poly sheeting under gravel is most common) and installing the vents so they're cross-ventilated. That would mean near the corners. By my math, that's less than 1 square foot of vent opening.

Section R408.2(exception 2) is the one that prohibits operable (closeable) vents.
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Old 07-29-2008, 12:15 PM   #29
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i have cement "vapor barrier" completely covering everything down there.... guess that does not count?

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Old 07-29-2008, 01:55 PM   #30
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Whether or not cement is an effective vapor barrier would be a judgement call by the authority having jurisdiction. Personally, I would never consider a concrete slab as a vapor barrier, unless a vapor barrier was placed underneath the slab.

The code requires habitable interior spaces with slabs to have 6mil vapor barriers under the concrete. Your space isn't habitable, but I think that the code's requirement for a vapor barrier under a slab in a habitable space establishes the ICC's stance on whether or not concrete alone is an effective vapor barrier.

Concrete very effectively wicks moisture!

Nothing says you couldn't spread poly over the slab if it came down to it. I'd allow it, provided it were secured by a cover of gravel.

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