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-   -   Crawlspace Moisture - Serious Problem (http://www.diychatroom.com/f2/crawlspace-moisture-serious-problem-58955/)

PaoloM 12-10-2009 10:43 AM

Crawlspace Moisture - Serious Problem
 
Need some help :help: to manage the moisture in my crawlspace. I have a 16x32 cabin that has no electrical/plumbing and the only source of heat is a wood burning stove. Cabin Interior is all plywood and walls built with 2x6 lumber. Crawlspace has about 3-4' in height, floor is covered with 6mil Poly (ground is crushed stone). Crawlspace is closed off (Exterior Walls)with 1/2" pressure treated plywood (no insulation on crawlspace walls. The floor of the cabin is composed of (starting from top to bottom)...5/8 T&G Plywood, 3/4" OSB Board, 6mil Poly all on top of 2x8 Joists (Spruce Lumber) sitting on 2x10 Pressure Treated Wood Beams which are sitting on Concrete Blocks. In between the joist is R20 Fiberglass batts.

PROBLEM:
We are finding the poly that was installed on top of the Floor joists under the plywood is holding water from condensation. I’m assuming when we start the wood burning stove the heat from the interior and the cold in the crawlspace is building up moisture. The poly is literally pooling/sagging in between each joist.:eek:

QUESTION:
Do I…
-cut open the poly so any moisture build up drains and leave the fiberglass batts (will get wet from draining moisture) OR
-remove poly/fiber glass batts and leave the floor joists open OR
-remove poly/fiber glass batts and install rigid foam insulation in between the joist making sure the rigid foam is sitting up against the plywood in between joists and maybe put rigid foam insulation on crawlspace walls also. OR
-remove poly/fiber glass batts and spray foam in between joist and possibly spray foam the crawlspace walls

NOTE:
Currently there are no vents in the crawlspace and was told not to put any as it will be worse. Cabin is located in Southeastern Ontario, Canada. Winters are really cold and lots of snow which normally covers up much of the crawlspace perimeter so vents would be no good anyway.

Any help would be much appreciated. The cabin has only been built about 2 years ago so I want to make sure I deal with this problem now before the floors/joist rot out. :(

Thanks!

Paul

majakdragon 12-10-2009 10:54 AM

I agree that the problem is caused by the wood burner. I really think that the poly under the floor is causing more of a problem. Most moisture barriors for floors are on top of the subfloor. You have, basically, formed a moisture chamber inside the cabin. My homes crawlspace had faced insulation installed between the floor joists, and the facing was on the crawlspace side. This caused the same problem you are having. I removed the insulation, stripped off the facing and re-installed the insulation. I open the vents in the crawlspace during warm weather and close them for the winter. Hot temperatures will raise the moisture level and the vents allow air flow to dissapate the moisture.

Gary in WA 12-10-2009 11:02 AM

http://www.buildingscience.com/docum...n-crawlspaces/

Be safe, Gary

PaoloM 12-10-2009 11:58 AM

That was a great read! Now I just want to make sure I understood what I read...I Definitely need to remove the poly and fiberglass batts.

I have 2 options:
1. Spray foam in between and over all the joists so that the entire joist is insulated.
2. Install foil faced RIGID foam insulation under the joists (foil faced to ground). No insulation in between joists.

Do I need vents? Should I insulate the crawlspace walls with rigid insulation?

Paul

Gary in WA 12-10-2009 12:49 PM

Some building departments require foundation ventilation.

http://www.advancedenergy.org/buildi...l%20Spaces.pdf

http://www.eere.energy.gov/buildings...s/db/35379.pdf

http://www.fpl.fs.fed.us/documnts/te...entilation.pdf
Be safe, Gary

PaoloM 12-10-2009 02:04 PM

I think the biggest problem I have is the fact that this cabin has no electrical which means there isn't a constant temperature. When it's being used during the cooler months we have the wood burning stove going which drives the temperature way up where as when we are not there, its cool inside and probably the same temperature in the crawlspace.

Vents in the crawlspace are open to so much debate. Not sure what to do!

Paul

Gary in WA 12-10-2009 04:46 PM

Lacking any heat ducting in the crawl, I would leave the vents open, closing them off only while occupied. (after doing the floor insulation).

Be safe, Gary

PaoloM 12-11-2009 12:11 PM

So you are suggesting once I insulate the bottom of the joists I should cut out vents on the walls and only open them when I am using the wood burning stove?

1. How big/many vents would I need for a 500sq/ft crawlspace that is approx. 3-4' in height?

2. Do I cut out vents at the top/center of the crawlspace walls?

3. Do I need to keep them open during the summer at all?

4. For insulating the bottom of the joists would reflectice foil roll insulation be a good idea? much easier to install vs. rigid foam. I was thinking of using this product under the joists and possibly on the inside of the crawlspace walls... www.reflectixinc.com

Thanks!

Paul


Wildie 12-14-2009 09:21 PM

I have a place in s/w Ontario, also! It has a crawl space with 6 mil plastic spread over the earth and weighted down with large stones.
The perimeter is closed in with 8" concrete blocks!
Insulation (R12 Roxul) is fastened to the inside of the concrete blocks with insulation pins. The Roxul is covered with 6 mil plastic as a vapour barrier. This is stapled to the rim plate at the top and the insulation pins lower down.
I have closed off the vents permanently and covered these with insulation.
I have made the crawl space part of the conditioned living space by supplying furnace ducting into the crawl space.
In our area, in the summer, moisture is carried into the crawl space when hot, humid air comes in, through the venting and then condenses against cool surfaces.
In your case, I suspect that the moisture enters the building in the summer and then it condenses against the cool surface of the plastic vapour barrier.
For your case, I would remove the insulation and vapour barrier from the floor and use it around the perimeter skirt.
I would insulate the walls and ceilings of the cabin and make sure it is well sealed with a vapour barrier on the inside. This will form a vapour barrier on all exterior surfaces.
In the summer skirts would be vented, along with the windows being opened, while you are staying there, but close the vents and windows, when the place is unoccupied!
The idea is to keep hot, humid air out of the building and keep it from condensing on cool surfaces.

Wildie 12-14-2009 09:27 PM

I have a place in s/w Ontario, also! It has a crawl space with 6 mil plastic spread over the earth and weighted down with large stones.
The perimeter is closed in with 8" concrete blocks!
Insulation (R12 Roxul) is fastened to the inside of the concrete blocks with insulation pins. The Roxul is covered with 6 mil plastic as a vapour barrier. This is stapled to the rim plate at the top and the insulation pins lower down.
I have closed off the vents permanently and covered these with insulation.
I have made the crawl space part of the conditioned living space by supplying furnace ducting into the crawl space.
In our area, in the summer, moisture is carried into the crawl space when hot, humid air comes in, through the venting and then condenses against cool surfaces.
In your case, I suspect that the moisture enters the building in the summer and then it condenses against the cool surface of the plastic vapour barrier.
For your case, I would remove the insulation and vapour barrier from the floor and use it around the perimeter skirt.
I would insulate the walls and ceilings of the cabin and make sure it is well sealed with a vapour barrier on the inside. This will form a vapour barrier on all exterior surfaces.
In the summer skirts would be vented, along with the windows being opened, while you are staying there, but close the vents and windows, when the place is unoccupied!
The idea is to keep hot, humid air out of the building and keep it from condensing on cool surfaces.

PaoloM 12-15-2009 11:34 AM

My cabin stays cool in the summer...very comfortable on hot summer days. The cabin was built with 2x6 lumber and was insulated very well on the walls and in the attic. Vapour barrier was done well also.

I'm definitely going to remove the vapour barrier and insulation in the joist of the crawlspace. I'm thinking about installing rigid foam insulation around the crawlspace walls which are 1/2 plywood. Then I think I'm going to use that foil bubble wrap and mount it under the joist like one big blanket.

In the summer we normally have the windows open when we are there, sometimes at night we even put the wood burning stove on to get the dampness out of the cabin....but it's not on for too long, just enough to get rid of the dampness in the air (if any). We did not have any sweaty walls/ceilings in the cabin this past year which I'm glad about and hopefully it stays that way. The only "sweat" we get is inside our kitchen cupboards...only in the winter, but goes away once we keep them open to air out and have the heat circulate.

Paul

Wildie 12-15-2009 02:35 PM

The foam insulation on the inside of the 'skirt' seems like a good idea to me!
I don't understand what function the 'bubble wrap' would perform. I'm ambivalent about this! I do know that its not a good policy to have two layers ( plastic on the ground and bubble wrap above) of a vapour barrier in place, as it will trap moisture in between.
Would you consider using floor vents into the crawl space, so that it becomes part of the conditioned space, as well?
I once had a duplex (an older building) that had sweating on the inside of the cupboards. I stopped this by gluing 3/4" stryrofoam on the outside walls.


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