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  1. #1
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    as usual, our outdoor relative humidity at 6am is 75%, even with the temp at 15F.
    probably stay such till 10am+, as usual.

    so, it makes NO sense to vent crawl spaces here in Huntsville AL --

    so, review the NOAA data for the area where the house is -- if one is not by a posted city, check olsters.
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  2. #2
    Join Date
    Nov 2004
    Location
    Naples, Fla.
    Posts
    1,403
    Have you looked into the info on

    http://www.buildingscience.com/resou...ld/default.htm

    How does that match up for you?

  3. #3
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    I am familiar with BUILDINGSCIENCE.com & CDC.com

    -- your link was to many articles about mold --
    I do not understand your point --

    my mold issue went away after I sealed my crawl, extended downspouts 10+ ft, dug ditches on upper side of my house, run dehum in crawl 24/7.

    today- outdoors
    4a = 17F 69% RH 8a= 21F |86% 9a=28F | 69%

    [Edited by cem-bsee on 12-09-2006 at 10:41 AM]
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  4. #4
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    today, 2/11/07: 5a=19F&18 dew 6a=19/19.
    2/9: 4a=28F/12 dew same at 5a.
    2/10= RH% OD was 65 = low for us
    2/2 6a= 30/21
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  5. #5
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    to continue: -- for those who wanted dew point:
    2/19/07 -- 6a= 23/23F 8a= 32/28F = dry/dew = sunny
    forecast: maybe rain tomorrow, mid50s at midday today
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  6. #6
    Join Date
    Mar 2002
    Location
    Richmond, Virginia
    Posts
    4,264
    I'm with you all the way cem. Keep that soup out of the crawl space!
    There is nothing more frightful than ignorance in action....Mark Twain

  7. #7
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,364
    Quote Originally Posted by ;1300695
    as usual, our outdoor relative humidity at 6am is 75%, even with the temp at 15F.
    probably stay such till 10am+, as usual.

    so, it makes NO sense to vent crawl spaces here in Huntsville AL --

    so, review the NOAA data for the area where the house is -- if one is not by a posted city, check olsters.
    I agree, do not vent the crawlspace. Its warmer during winter and drier during the summer. But consider, if the crawlspace does not have plastic on the earth(most don't), venting has big a drying benefit. If the crawlspace is 50^F, venting 15^F, 75%RH equates to 17%RH when warmed to 50^F. Of couse So the 75%RH outside air dries the crawlspace and home. This confuses many.
    Here is a calc to figure dew point from temp/%RH.

    Given temperature at 80F and rh at 70%

    1. 100% - 70% = 30

    2. 30/3 = 10 (if humidity 30-50 then divide by 2.5)

    3. 80 10 = 70 (approx dewpoint temp)



    Example at 50%

    1. 100% - 50% = 50

    2. 50/2.5=20

    3. 80-20=60

    Your temperature at 15F and rh at 75%


    Example at 75%

    1. 100% - 75% = 25

    2. 25/3=8

    3. 15-8=7^F dew point


    Email me your address, I will mail a Psych chart calculator. TB

  8. #8
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    yes, my crawl has pvc over the dirt--

    temp about 44F with OD at 15.

    to have a calculator would be nice --
    I've had a chart for some time.
    look in Tech Forum, pls
    Last edited by cem-bsee; 02-20-2007 at 06:20 PM.
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

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