Odor from Crawl Space

lisabarron

MurphyMan, We are having the exact problem in our home after encapsulation. We are considering mitigation, so just wondering if it worked for you. Thanks!

MurphyMan

Yes, it worked. Within 24 hours, after we turned the fan on, the smell in the house was gone and it was fairly easy to do.

I installed the system, pretty much as shown in the sketch in my previous post. I took a Tee off at the center of the array. From there I used solid 4" PVC and ducted it horizontally into the adjoining garage, then on up. I installed the radon fan in the garage attic, then vented it through the roof.

The other day I stuck my nose into the rain trap I built in, to see if the odor was still present in the exhaust air. I thought perhaps that a month of running the fan would have removed the smell, but yes, it still stunk. The system is an unqualified success.

I do wonder if pulling the air out from under the crawl space will affect our utility bills. I guess that verdict is out for the moment.

Murph

lisabarron

Thanks for your quick response!

hand drive

pulling air from a sealed crawlspace does not seem feasible. where is the air being drawn from.

pucks101

I don't think they're trying to imply any kind of true "ventilation" of the crawl space, but more of an "evacuation" of off-gassing from the earth under the vapor barrier. Tthey are only using a small radon gas fan to help create a chimney effect through some PVC vent piping.

Sounds fairly promising so far....

MurphyMan

That is a good question. I'm not 100% sure where the air is being drawn from. I think the fan is 175 cfm and if you put your hand over the vent, the air blast seems fairly strong.

The house is about 30 y.o. and is of fair construction. I sealed the crawl space using recommended methods; replaced the vents with cinderblocks, overlapped most seams a foot, used high quality materials, ran sealing tape along the foundation blocks then secured to the wall with pins, etc.

Still, I know there is still some leakage between the liner and the foundation. For example, there are about 8 support pilings made of cinderblock. I know there is leakage there, due to the irregular shape of the end of the blocks and other places.

A further item, I installed a register in both the conditioned and return air ducts, in the crawlspace. This is per current state of the art for encapsulating crawlspaces. I am sure the system is pulling some of that air through the liner leaks and into the soil gas mediation array.

But, the end result was the fan is doing it's job. No more stinky.

John_W

MurphyMan,

You seem to have discovered the reason for the same, but localized smell in my crawl space.

I had/have the cat pee smell in my radon mitigated crawl space. It was/is in just one corner and it didn't start until a year or two after we installed the mitigation system. I always assumed that some mice or squirrels did the deed during a particularly cold winter. [I found nuts hidden in the insulation between the floor joists in that corner - near the crawl door.]

However, no amount of investigation showed signs of pee (I used ultra violet light to search). And, no amount of cleaning or odor removal helped - except for a few bags of odor absorbing material near the junction between the main return duct and the HVAC machinery. The odor in the crawl in that corner is gradually fading over the last two years, but it still is noticeable on very warm, humid summer days.

Anyway, the under-radon-barrier ducting doesn't have a branch in that area. It could be that lack of suction in that corner has allowed the pee smell to seep up into the crawl!

MurphyMan

Can you run a branch in that area? Please report back if it works - or if it doesn't.

Murph

John_W

Yes, that should be possible.

It will be a while though before I can get around to it.