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Is there a proper way that is considered "code" to block off crawl space vents due to humidity being pulled in? My crawl space insulation has a slight damp to touch feeling sometimes in the morning, especially lately. I just want to do it correctly and neatly, especially if I sell my house in the future.
Humidity generally comes from ground moisture. Is the ground under the house covered with an impermeable plastic moisture barrier? How about the walls of the space? If it is concrete block, substantial moisture can be wicked into the block and then the crawl space. Venting to the outside can draw air in only if there is a substantial wind or a low pressure situation, such as the intake air for a furnace being pulled from the crawl space.
Put a good black plastic 6 mil water vapor barrier down on the ground and overlap at least 12 inches any seams. Leave it for a while (30 days) and check the situation out to see whats going on after the install before you make any attempt to close your vents off.
The vents are there to ventilate the space and should not be closed off.
Thats step 1.
There may be more steps depending on how this turns out.
I have had a continous 100% ground coverage vapor barrier. I just lately have my floor joist insulation become damp to touch in the mornings especially. I am currently looking at sealing up the holes I found in the Air Conditioning trunk to see if the cold air escaping is causing the crawl space to be more cooler than the outside are thus casing condinsation. I thought I woud try that first before I sealed up the crawl space and put a dehumidifier down there. I had to waterproof the outside of the house on two sides earlier this spring because it was leaking in under the vapor barrier. I thought that would take care of my moisture issues, but the insulation being damp just started occurring again about a week or two ago. I'll see in the morning what is up as I had the air condition people come in and seal quite a few punctures in the trunk. It does feel warmer in there already though. I don't know if its a good thing? It had been awful cool in there before. Maybe just wishful thinking?
What I would do is insulate the outside walls of your foundation with r-10 ridgid board, pull the insulation out of the floor joist and use your crawl space as conditioned space. you will have to install a fan and a transfer grill. This should solve your problem and your floors will be warmer in the winter time.
would blue boarding the foundation vent holes and putting a dehumidifier down there (which I already have 70 pint low temp) with it hard lined to the AC condensation line work as well? I don't seem to have any plumbing leaks/gutter issues etc..... The ground under the vapor barrier is anywhere is not wet. I guess it could be coming out the block in a vapor type from that you can't see?
Yes,
If you get an r-10 insulation value from the blue board ,you would also be closing the vents tight. This is a very good pratice I'm sure will solve your problem.
The key word here is "conditioned". You are really making the crawlspace into a mini basement, so the heat and air conditioning need to be directed into it. It also has to be completely sealed.
If you miss any of the steps, you could be creating a huge problem. The interesting thing about the sealed crawlspace topic is there is a vast difference of opinion on how effective it is.
If you are considering sealing your crawlspace, I suggest you do a lot of research on the topic, and follow the recommendations to the letter.
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