Crawlspace odor control

[edabal]

My 10 year old Indiana house has a vented (unheated) crawlspace with 5 automatic vents. The earth is covered with plastic wrap that is not sealed against the walls or columns. The sub-floor has no insulation and the walls have 1” rigid foam insulation. A sump pump is installed at the lowest corner.

This year, we started to get a musty and sour odor in the living space above the crawlspace for the first time. Our carpet is kept clean, we have no pets and no smokers. I had an expert examine it for mold and I was told it was dry and clean -- I checked it out myself and found nothing other than the unpleasant earthly smell. The expert recommended laying down a new plastic wrap which he recommended to be sealed tightly against the walls. He said the small gaps in the plastic wrap on the earth are causing water to evaporate and cause all this smell. I find this hard to believe, will a tightly sealed wrap solve this problem?

Regardless, I have decided to lay down a new wrap according to the instructions he gave me. I still have a lot of questions though.

- Should I keep the old plastic wrap and place the new one over it, or should I remove the old and install the new plastic wrap in its place?

- Should I remove the rigid foam insulation on the walls to place the wraps on the walls behind them and then put them back on the wrap?

- If that doesn’t stop the odor, will placing a plastic wrap directly on the sub-floors help control the odor from seeping into the living space? A friend noted this could be a recipe for mold on the sub-floors since it might trap moisture there.

I appreciate any insights into this.

[majakdragon]

edabal, Welcome to the DIY Forums.
I would not remove the old plastic. All you are doing is making it a thicker barrior.
If you can, I would run the plastic behind the foam. This will make a tighter seal for the plastic.
Going into winter I believe the humidity levels are increasing and this could be the reason you are getting the smell. Try the above before putting plastic on the subfloor.
Good luck.

[industry-links]

sealing the plastic is the most important factor here. When you do this, you encapsulate the crawlspace from moisture penetration. Think of it like a ship in the ocean, they seal those pretty good don't they? :)

Also, make sure to seal the plastic to the floor joist. Any gaps will allow airflow and moisture into the crawlspace.

I've never used these, but I've heard of small buckets of a charcoal-like substance that absorbs much of the odor and moisture problems like you mention. I believe they are sold at Home Depot and Lowes, but I do not know a name brand. Perhaps someone else can help with this.

[edabal]

I started work on laying down the plastic wrap on the floor (on top of the old wrap) and sealing it against the wall. I only finished 40% of the area, but the largest previous gaps have been sealed. Sadly, the odor doesn’t seem to be ceasing at this moment and I feel let down that when I’m done, the odor will continue.

I do want to place the plastic wrap directly on the joists, but I’m worried it will cause moisture to be trapped causing damage to the joists. Is there any expert who actually recommends this?

It’s funny you mention how they seal ships well. My grandfather captained an ocean freighter and he once commented that unlike basements, his ship will never let in water from the sides, despite the fact that it’s deeper in water than the entire height of his house and that it sits in saltwater almost ceaselessly.

[industry-links]

Take a look at this product: Cleanspace. Its a patented product tha we used to sell, manufactured by Connecticut Basement Systems. They have dealers all over (which is what we are). Might be another idea for you:

http://www.primoid.com/n_cleanspace.htm
http://www.cleanspacenorthwest.com/process.html
http://www.permaseal.net/Cleanspace.htm
http://www.jlbasementwatercontrol.com/Crawl%20Space.htm