Crawlspace Mold / Encapsulation / Dehumidification advise
I am new to the forum and need some advise. We have a home that is just over a year old and was new when purchased. This past summer we had a lot of rain and the weather was very humid.
About two months ago, I notice some hardwood in our dining room was cupping and thought "moisture". I opened the crawlspace and looked around the foundation of the home, but did not find any leaks, standing water, or any sign of water staining on the blocks. However, it was very humid in the crawlspace. The space does have a moisture barrier, but it was poorly installed with gaps between the sheets and it does not meet the walls in many places. Anyway, when I took a closer look at the joists and OSB, I noticed mildew and light green mold in patches throughout the entire crawlspace. I did some reading and decided to seal the foundation vents and add a standard home type dehumidifier and directed the drain hose about 15ft outside through the foundation drain. Since then, the humidity has dropped to about 55% avg throughout the space.
I have received three quotes on cleaning up the mold and mitigating it's return over the 1900 sq ft. of flooring.
Quote 1) Fog the entire space with moldicide, leave the existing cheap vapor barrier, cover the walls, and piers, with new 6mil plastic sealed in place with treated wood strips about 10 in. below the sill plate. Then, install new 12 mil plastic on the floor and cover all seams with tape to create a encapsulated space. Cost: $6750.00
Quote 2) Spray the entire floor with Bora Care w/ Mold care. Then, return a few days later, remove existing vapor barrier, cover the walls, and piers, with 6mil plastic (Clear) sealed in place with treated wood strips up to the sill plate. Then, install 10 mil plastic on the floor and join together with tape to create a encapsulated space. Finally, they want to add a Dry-Space Plus dehumidifier and install a new access door. Cost: $4600.00
Quote 3) Soda blast the entire floor space and joists to remove the mold, follow up with hydrogen peroxide solution sprayed on the floor space, remove the old vapor barrier, install a new 6 mil barrier on the floor (no walls, or tape, just overlap and bring up to the walls), install a SaniDry CSB dehumidifier and a new access door. Cost: $5250.00
Quote 1 is a local company that is not franchised and they offer a 3 yr warranty. Quote 2 is a larger nationwide franchise with a 10 yr warranty, but they indicated they don't normally tape all of the floor barrier seams, just enough to keep everything fastened. Quote 3 is a large franchise that sells high end encapsulation systems. However, the tech said he did not see a reason to install a system (no indication of any water just humidity) and recommended getting rid of the mold, install a dehumidifier and keep the vents sealed.
I know this is a long post, but I don't know which way to turn. I would really appreciate any insight from the fine folks on the forum. BTW, we are located in AL where the summers are very hot and humid.
Keeping the space dry makes mold dormant. Removal is required if occupants are sensitive to dormant mold. If not sensitive, dormant mold will not effect the structure. Just looks bad. Odor will subside. After you get tired of replacing the residiential dehus and high energy cost, a get dehu designed for the space, like a Santa Fe Compact. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Think of making your crawlspace like a conditioned basement. Since you live in the southeastern part of the country and probably have duct work in the crawl space if you encapsulate take TB's advice one step further and add a fresh air intake that is connected to an Energy Star rated dehumidifier and dump most of the dehumidified air into the ductwork. A conventional air conditioning system cannot dehumidify without a call for cooling. The more efficient A/C systems are doing a poor job of keeping the inside humidity under control and keeping the home comfortable at the same time. In HVAC talk they have a higher sensible heat ratio that the less efficient units. If you had multi-colored fuzz growing under the floor there is a possibility that you have/had their relatives growing in your carpet, curtains and mattresses too. This summer's high number of warm and raining days in the SE kept most homes above 60% relative humidity. Check out the research on www.crawlspaces.org, make the crawl space as tight as possible and see if you can live with the dormant fungi/bacteria after they finish off gassing as they dry up.
Originally Posted by teddy bear
Thank you for the reply. The SaniDry CSB dehumidifier in Quote 3 is a re-branded Santa Fe Compact. They look identical and have exactly the same specs.
Right now, I am leaning for toward Quote 3 (I have mold allergies) with continued monitoring throughout the next year. I can always go back and add the encapsulation if needed.
Could you have the Foam Sprayed on the Floor Joist, and Bottom of Floor, (From Underneath) Saw an attic where that stuff was sprayed on the Roof Rafters, and underside of decking. Looked vapor proof, but wasn't sure. Imagine any chemical in the stuff would kill the mold, and you'd have an insulated floor.
Remember, Air Conditioning begins with AIR.