Replies

1. 
   [email protected] | May 30, 2009 08:54pm | #1

   In your climate I would definitely advise against closing them off. even in the winter.

   To the best of my knowledge, "dry" is an impossibility in your climate. Things may be less damp, but never "dry".

   You are always going to have condensates there, and always should provide a vent to help them dissipate.

   I'd recommend: increasing the insulation around your pex pipes and floor; and leaving the vents open.

1. 
   Clewless1 | Jun 07, 2009 06:23pm | #3

   With all due respect, I'm sure ... hogwash! In the Northwest, it is routine to close vents in the winter. It's a misnomer that Seattle is always rainy/damp. It only gets 34 inches a year .... in terms of relative rain, that isn't a lot. I worked in the NW for 20 years and we always advocated closing vents in the winter (with the blessings of the BO). If he has poly on the ground to control moisture, generally he should be OK to do this (barring being in a low spot w/ e.g. high ground water, which it sounds like he is not). I am not going to comment on permanent closing of vents at this point.

1. 
   levelone | Jun 07, 2009 08:53pm | #4

   I am also in the PNW and have wondered about this issue.  In newer construction with well insulated ducting and floor, what is the benefit to closing the vents during the winter?

1. 
   Clewless1 | Jun 08, 2009 08:37am | #9

   Benefit closed:  Your floor is now exposed to a [potentially/theoretical] warmer temperature ... say around 50+ degF rather than the cold outside. Less heat loss. Also warmer floor surface ... the only part of buildings we routinely 'stay in touch' with.

2. 
   rjw | May 30, 2009 10:25pm | #2

   Check the Building Science website discussions.

   In my area and climate (NW Ohio, with hot humid summers), it's probably more important to close the vents off in summer: If it's hot and humid outside, and I bring some of that hot humid air into a relatively cool crawlspace, I'm increasing the amount of condensation in the crawl - This is basically counter-intuitive but makes sense in many/most climates after you think about it.

   But, I'm most familiar with forced air systems where some de-humidified conditioned air is getting in the crawl space (by design of system leakage)

   ---

   "Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."

   Howard Thurman

   ---

   http://rjw-progressive.blogspot.com/

1. 
   JHOLE | Jun 08, 2009 03:36am | #6

   Ya ready?

   I agree 100, no wait, 99%.

   Gotta throw that 1% for safety....Remodeling Contractor just on the other side of the Glass City

3. 
   Pelipeth | Jun 08, 2009 02:59am | #5

   Isn't it nice to have the option, personally I like vented spaces, air movement is a good thing.

   
   

   ---

   Edited 6/7/2009 8:01 pm ET by Pelipeth

4. 
   Piffin | Jun 08, 2009 05:06am | #7

   based on your description, I'd leave it closed, but check things once a month to be sure.

   Here, summer is the worst time to open crawl vents.

    

    

   Welcome to the
   Taunton University of Knowledge FHB Campus at Breaktime.
    where ...
   Excellence is its own reward!

1. 
   redoak | Jun 08, 2009 05:24am | #8

   Piffin,What would be the obvious things to look for, aside from the smell and/or sight of mold and mildew? I'm just curious: what happens up your way with open crawl spaces?Here in Seattle, humidity during the summer is very rarely a problem. We get minimal rain during the summer. We get a fair amount of rain in the winter, but I noticede that the heat from those pex pipes kept the crawl spaces slightly dry and slightly warm even.

1. 
   Piffin | Jun 08, 2009 03:04pm | #10

   Lots of summer fog and humidity rolls in on the warm air and when it gets into a cool crawl, it condenses so you see 2water running down vertical surfaces.
   I know of a couple with plastic on the ground that will grow puddles on it during summer.Fall is usually pretty dry air and temps between crawl and outside air are stabilized. Winter way too cold to leave a crawl open 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

1. 
   redoak | Jun 09, 2009 08:17am | #11

   Wow, I can see why open vents in your part of the country whatever the season would have serious consequences.