I have the crawl space decked out as a mini-basement and intend on warming it along with the house (in a week or so)…….I am getting a moisture build up along the inside surface of my TJI rim board and not sure why. I have blue board on the block and r-13 batt stuffed into the channels between the floor joists.
Could this moisture build-up be because of the tyvec that covers the ext side of the rim? It was wet before I insulated even, but I thought the vapor barrier would stop it…….it’s not.
Any of you guys have experience with this application? I never dealt much with crawl spaces, but it seems to me that moisture shouldn’t be building alongside the inside of the rim………..how to control it?
Replies
The two types of moisture that affect your CS are the wicking up through the wall and the increase in humidity from the moisture that evaporates in the CS.
Is your drain depicted accurately as being above the footing? If so, this would allow the base of the wall to remain wet. The moisture will wick up through the wall.
If the vapor barrier in the crawl space does not truly seal off the area under the barrier from the crawl space, some of the moisture will serve to increase the humidity.
If the outside temperature is low enough at the exposed wall to be below the dew point, moisture in the air in the CS will condense on the wall above the insulation. It is usually not a good idea to place insulation inside a basement.
Placing the insulation outside helps to reduce the effect just described by not allowing cold air to access the wall. Thus the wall tends to be warmer than the outside temperature and approaching the warmth of the CS air. This reduces the dew point condensation effect, which is the primary culprit in producing palpable moisture on the concrete. The area that is exposed above the insulation on the outside as well as then entire inside wall surface can thus "breathe."
Two things you can do relatively inexpensively:
Put vents into the crawl space to reduce the CS humidity.
Put a sump pump inside the CS that will keep the water level well below the footing to reduce standing water under the gravel.
Is your drain depicted accurately as being above the footing?
Yes, but the footer is in a ditch.....the actual inside floor is above the footer.......also I'm not totally back filled......but I have a drain inside the crawl space to capture the water that may get in under the plastic.
I'm wondering if the tyvec is keeping the moisture from exiting.......no?
A thought is to cut the tyvec back to the bottom plate of the stud walls and even drill a few holes through the rim to allow the moisture to exit.......no? That way I can still warm the crawl space.
I'm kinda committed to doing the inside the crawlspace with insulation now that it's already done........probably should have gone exterior at least on the hill side.
I KNOW I cannot leave as is............once I heat the house proper it will probably get worse.
You also have the moisture from construction. IE, lumber drying and DW mud drying.
But I suspect that the problem is the FG insulation.
Is it sealed tight at all edges?
Air, with moisture, is probably getting behind the "paper". But the FG is provide some insulation so it is cooling off.
Pull it out and cut blue board to fit and then use a foam gun and run a bead all the way around to seal it in place.
Air, with moisture, is probably getting behind the "paper". But the FG is provide some insulation so it is cooling off.
I think so cause I just went in there and checked behind some of the FG batts and it was soaked.........I tore it all out.
This is what I have now.
I'm wondering if there is some kind of foam machine I could rent and just fill the cavity. the problem is that these are TJI's and they have the I shape. I think wet air is just going behind the batts and condensing like you said...................If I could foam that area it would lock it out.
You need to see how much volume that you need
http://www.fomofoam.com/index.htm
They have both the 2 part foams 1 park. If I remember correctly they have the 2 part in both one shot botles and refillable systems.
You might want to get the gun and one part anyway for the sealing all of the other places in he house (around windows, attic penatrations, etc).
And here is there commercial web site. It might have more technical details.
And here is another source, look under building products.
http://www.sheltersupply.com/
My understanding is that the Tyvek should prevent water from getting through in the liquid form; however, the water vapor should be able to escape. Therefore, it should not be causing the problem.
Why do you want to warm the crawl space? If it is to keep the area above warmer or cooler, it might be better to insulate between the joists. As long as there is moisture getting into the air in the crawl space or into the wall by wicking, there will be a potential for moisture to collect on the masonry whenever the temperature of the masonry gets below the dew point.
Les Barrett Quality Construction
Why do you want to warm the crawl space?
Well, it sounded like a good idea......never done it......my house.......I bought into the mini-basement philosophy....... and I didn't want to insulate the joists. Now it will be a bear to do cause the upper house is in the drywall stage.
>>Why do you want to warm the crawl space? FWIW, in my area (NW Ohio) conditioned (heated and cooled) crawlspaces are becoming the norm, and such crawl spaces rarely have moisture related problems, (mold, rot) even when there is significant water in such a crawl.The key to forgiving others is to quit focusing on what they did to you, and start focusing on what God did for you. Max Lucado
Sojourners: Christians for Justice and Peace
The moisture along the rim joist is good old condensation.
The question is where is the moisture/water vapor in the air that is condensing coming from?
Is this new construction? Are the exterior water controls sufficient?
Is there a plumbing leak? Is there a combustion flue in the basement improperly connected? (Very dangerous!) Is the dryer venting into the crawl?
Is the crawl vented and have you gone from relatively damp atmosphere to suddenly cold?
Where are you located?
The key to forgiving others is to quit focusing on what they did to you, and start focusing on what God did for you. Max Lucado
Sojourners: Christians for Justice and Peace
where is the moisture/water vapor in the air
Well it's pretty damp in there cause of all the rain etc. when the area was open. I kknow it will take an effort to dry, but the condencing has me troubled.......I hate water laying around like that.......new construction.........backfill not yet complete on hill side.........the drain tile seem to be doing a good job, but I'm sure some is getting under the footer cause it's serious clay.....in somr areas so serious I could make a pot out of it.
Is the crawl vented and have you gone from relatively damp atmosphere to suddenly cold?
No vent, but the outside access is open...........damp to cold.....yes ....I'm in south central OHio
Plumbing good......no flues in crawl space
You have to dehumidify that basement. Clay is horrible...
blueWarning! Be cautious when taking any framing advice from me. Although I have a lifetime of framing experience, all of it is considered bottom of the barrel by Gabe. I am not to be counted amongst the worst of the worst. If you want real framing information...don't listen to me..just ask Gabe!
I'd guess this is a "one time thing" and I'm with blue - dehumidify now, and monitor until after all construction is done.Our climates aren't all that different and I don't see a need for you to "foam" the box ends.You're just getting the typical "darn, it turned cold fast" condensation, especially common in new construction.The key to forgiving others is to quit focusing on what they did to you, and start focusing on what God did for you. Max Lucado
Sojourners: Christians for Justice and Peace
Edited 11/15/2004 4:41 pm ET by Bob Walker
"one time thing" and I'm with blue - dehumidify now
Will do for sure........You wouldn't happen to know exactly how they are doing crawl spaces in your area do you.