ventling issue

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Old 11-23-15, 04:17 AM
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ventling issue

Have a crawl space under breezeway that connects house to garage; vapor barrier was placed on the ground a cement slab was installed and I had requested pressure treated floor joists since there was no code locally for venting such an area. Well, due to the fact that a gutter elbow got fractured at the roof valley by an ice jam (not sure when) and no evidence of water damage until people in the breezeway heard cracking...........pulled up the floor and most of the joists had rotted at the wall where the water had simply gushed out of the damaged gutter elbow over who knows how long (north side of house and under a deck). The blocks had filled with water, (floor was dry and only damage to the joists at the north wall. Well, contact called for pressure treated joists and of course contractor has since past. All new floor joists have been installed, sill plate replaced etc and the question came up regarding venting or in this case lack of venting. Ventiing on the north side would be out of the question since there is no way to open a close that vent since the deck is fairly tight to the house. First, a company is coming in to fill blocks with foam, foam all the walls in the crawl space as well as the sill and floor area on the north says it will protect everything and is used where venting cannot be done for one reason or another. Now......gentlemen did the work suggested cutting a couple holes in the sill plate in the garage and inserting 1-1/2 pvc with a protective screen over the hole which would allow air from the dry garage to move into that crawl space and by placement and design would keep rain or snow away from it and critters from entering the vent pipe.
Any thoughts on this? Guess I looked at it as some air is better than no air, only way moisture got in their was due to the bad elbow allowing huge amounts of rain to s it on the ground and eventually create damage...that has all been corrected with larger gutter........and with the foaming of the blocks both inside and interior wall.......water problem should be arrested.
Love to hear some feedback, I suspect many who have done crawl spaces have learned some good things over the years.
 
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Old 11-23-15, 06:42 AM
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In the cold north a crawlspace is usually not vented and with all of the insulation down there it would be counterproductive to vent. Being well insulated, can that space be opened up to the conditioned basement? Where is the access to this crawl?

Bud
 
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Old 11-23-15, 07:07 AM
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Bud905 1 info

Thanks for the response. was never insulated since it is only used between April and November...kind of like a season room. Maybe that is why this guy that does the insulation made the statement that when he gets done filling blocks north and south, covering them with insulation (this is all foam), venting would not be necessary. He said and I agree.."only reason you had moisture under there was the fact that the gutter elbow dropped so much water under a deck area that gets no sun and never had a chance to dry out and finally got pulled up or into that row of blocks of the crawl space and that moisture sitting there festered for who knows how long. Now that the gutter and elbow have been upgraded to a larger size there would not be significant moister to do what it did before. Good lesson, contractors simply use the standard 5" K gutter and in far too many cases, especially where there is a valley in the roof, it cannot handle it!.

Hope this helps answer your question, The guy that do the forum have so much experience sometimes their information has so much value.
 
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Old 11-23-15, 08:36 AM
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His statement "only reason you had moisture under there was ..." is not entirely correct. Moisture vapor moves from wet to dry until the moisture levels are equal and it can move right through those block (or concrete) walls. With no escape, other than through the floor above, the moisture level will climb to almost equal to the soil outside. The traditional coating of tar on the outside of the foundation will not stop moisture.

Depending upon the density of the foam he applied, open cell or closed cell, the crawl area should now be insulated and now needs to be conditioned. If the living space above is not conditioned year round, then this space will need a dehumidifier and a place for it to drain.

Gutters in our abundant snow climates will often fail so plan on this event happening again. The grade outside should no allow water to pool next to the foundation for any reason.

Bud
 
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