[boondocks95]

Just a quick question, we have a humidity issue in our crawlspace and some mold (but doesn't appear to be abnormal or abundant). We have looked into encapsulating and a dehumidifier.

That being said, we are going to test for radon as well since we were naive and our realtor never mentioned or suggested it four years ago. Where we live, there is a 50% chance our radon levels would require mitigation. If so, I would like to try and tackle both the mold and radon mitigation together.

I'm wondering if the radon system (encapsulation and then the fan/pipe) would possibly address the mold. The radon experts say that it should because it would draw moisture out of the crawl space. If it doesn't, I assume we could just install a dehumidifier at that time?

Can I address both issues together? Also, will be ductwork require cleaning and/or replacing if the existing mold is cleaned off? (The mold expert suggested cleaning but I am hesitant since we have flexduct, with the main trunk being rigid).

 

[GottaFixIt]

I recently did just as you describe. I encapsulated my crawlspace and installed an active ventilation mitigation system. It was extremely effective and I feel qualified to advise.

I believe the answer is "probably". As in it will probably take care of the humidity problem. I did see a decrease in the overall basement RH when I installed the Radon mitigation. It went from about 42% RH to about 35% RH.

There's a caveat here, though. When I insulated and encapsulated, the ambient temperature went up (thanks to the new R13 insulation and air sealing). This naturally decreases the relative humidity.

I'm certain that the fan is drawing some of the moisture out of the ground, but I can't really guess at how much. A 5 degree temperature swing can cause a 5% difference in Relative Humidity. It also affects the dew point, which is very relevant if you have mold growth.

What's your climate and insulation situation?

 

[boondocks95]

We are in the midsouth, have all four seasons. The insulation was shot when we purchased the house, falling down, etc so we ripped it all out and cleaned the crawlspace. You can literally eat off the floor. We put plastic down and installed the vents that automatically open and close.

When we purchased the dryer vent was broken and dumping hot air into the crawlspace which could have caused some of the issue. We fixed that obviously.

It doesn't appear that the mold has gotten worse but we haven't been monitoring it really. We did bleach under there a couple years ago which I know not to do now. We did that after the pest control people scared us to death trying to make a buck.

 

[TheSrProgrammer]

Bleach isn't the best chemical to use on porous materials. If the bleach was done with enough applications and enough exposure time, it should have done the job though. It's also a good idea to use a wire brush on materials like cinder block or other hard but porous surfaces and to sand down the top layers of any wood where mold was present. Encapsulation as a follow up step is a good idea because even dead mold can be allergenic. The encapsulation should not only inhibit future mold growth but also cut down on the chances that dead mold fragments contribute to health concerns.

Cutting down on the moisture and heat problems in the crawlspace is definitely good. I think ventilation for radon would help with the relative humidity in the space. Moving air over water will cause it to evaporate faster without any dehumidification process. However, having a house dehumidifier is a good idea for most everyone. If the radon fan is enough, then the humidifier will stay off the majority of the time anyway. I'm a little skeptical that it would actually be enough to replace fully the function of a dehumidifier, and I highly doubt it would be enough for certain weather conditions where excessive moisture is present.

Has it been confirmed you have active mold growth in your duct work? It's highly probable most HVAC systems have mold spores in them - and I don't think that's reason for alarm. It's only if the system has active growth that you should consider taking action. The first step is to figure out why there was enough moisture in the system to allow for the growth in the first place. Was it just from the humidity, or was it some sort of leak or condensation formation from the HVAC system? Treatment options: The bad news is there isn't any approved chemical or methodology to treat mold in flexible ducting. The training materials I've reviewed have explicitly noted this. The most likely best solution is replacement of the flexible ducting and a vigorous cleaning the rigid ductwork.

-TheSrProgrammer