Comments on: What Is the Best Way to Deal with Crawl Space Air?

By: Whitey

Whitey — Thu, 11 Jun 2015 06:32:59 +0000

The radon mitigation fan
The radon mitigation fan seems like a good idea.
I think that is the way I will go. Install 4 concrete block
plenum by laying the blocks on the side so cavities face the
4 crawl space walls. Fill with crushed stone. Then encapsulate
with a quality 20 mil barrier. If vapor pressure builds from organic
decomposition then I will have a place to tap into with the radon
mitigation system. The thinking is the fan thru the room would create
negative pressure under the barrier and pull air thru the soil to help
dry it out. Sure there will be rain see if the system can be timed not to
turn on during and immediately after rain. Just in case the vapor barrier
is not enough the plenum is there cheaply to tap into just in cast.

By: Tim

Tim — Wed, 10 Jun 2015 01:25:19 +0000

My 2,400 sq. ft. brick ranch
My 2,400 sq. ft. brick ranch house was built in southern Indiana in 2000. It has a crawl space that is 4 to 6 blocks high. It had the typical foundation vents. I closed vents in the winter and opened them in the summer. My living space near front door developed a bit of a musty odor only in 2011, mainly only noticeable in warmer weather. After a few inspections, no mold was found and the contractors have all appeared puzzled by the smell. After much research, I ended up closing the crawl vents year around, used foam board on inside to better seal them, installed new 10 mil vapor barrier and taped all seams. I went up the block walls about a foot and taped to block moisture. My block walls are all covered with blue board. I added a ventilation system, basically a radon system beneath the vapor barrier, and it pulls air 24/7 out one of the foundation vents. I also installed a dehumidifier in the crawl. While my crawl is staying pretty dry, I am still smelling that slight musty odor in my entryway to the right of my door especially. Thus, no help from the improvements. I have also noticed that my humidity in house goes as high as 59% now, depending on the weather. Any suggestions regarding odor or humidity? Thanks

By: Dave Morgan

Dave Morgan — Sat, 31 Jan 2015 21:06:29 +0000

We just completed a 1,600
We just completed a 1,600 foot "pretty good house" in NW Oregon. We opted for a conditioned crawl space and use our Lifebreatth ECM-155 HRV to provide continuous ventilation at the IRC specified rate of 32 CFM. We monitor the RH and temperature of the crawl and it has been consistently 3-4 degrees cooler than the living space this winter. The humidity now tracks perfectly with the living space which is maintained at 50% by the HRV. Air quality in the house is excellent, we could not be happier with this system.

By: Darlene Ranaudo

Darlene Ranaudo — Wed, 10 Dec 2014 20:58:26 +0000

Thanks David. Our builder is
Thanks David. Our builder is recommending putting in a Fan in the enclosed crawl to vent the bad air to the outside and have the outside air recirculate back in. Won't this bring moisture into the crawl? He is also trying to see if he can use some type of foil instead of plastic. Other option would be to replace the plastic to see if it is a bad batch or not. or just remove plastic altogether which means we don't have benefit of encapsulated crawl. It is just so strange that other homes in the neighborhood do not have this issue. Do you know of a specialist that could assist us with this as I am at a lose.

By: David Butler

David Butler — Mon, 27 Oct 2014 21:31:25 +0000

Note that soil gas mitigation
Note that soil gas mitigation solutions (i.g., fan-induced negative pressure below the liner) will not work very well unless the liner is continuous and sealed to walls and piers. I suspect if that were the case, the strong odor would not be seeping into the crawl space proper in the first place.

Before crawl was closed, the vents allowed soil gasses to escape. When the crawl is closed, it must be sealed properly, otherwise you end up with an unsealed closed crawl, which is a bad thing indeed.

By: Jeff

Jeff — Sat, 25 Oct 2014 00:30:15 +0000

Camille, I'm sure you read
Camille, I'm sure you read the threads here that this seems to be a problem for some of us. Our basement was also relatively dry but we had a pipe leak and it caused some mold. We overreacted with the encap and a dehu and ended up with a cat pee smell 6 mos later. Still have it. Think it's the organic earth gases of some kind. But not going away. We may try a radon fan as that seems to be an option. A neighbor is trying this as he had identical issue. Please post what you end up doing as many of us are still searching for a cure. I simply added a vent fan to pull some air through. It helps a lot but the smell does go away. It just gets more vented out. I'd like it to go away. Thanks. Jeff

By: David Butler

David Butler — Tue, 30 Sep 2014 23:10:43 +0000

@Kevin, vented crawl spaces
@Kevin, vented crawl spaces should be banned in the southeast. I'm from Charlotte, and I've never seen one that didn't have problems. Slab-on-grade and basement foundations are much more efficient than a vented crawl, and are less costly than an encapsulated crawl.

Since you already have a crawl space, you should definitely encapsulate. But I would hold off on the DH. It's not required by code.

If you address roof and site drainage issues, and the encapsulation is done properly, you're unlikely to need mechanical dehumidification. You can always add one later.

By: Ken W

Ken W — Sat, 13 Sep 2014 21:13:01 +0000

Musty crawlspace odor:&
Musty crawlspace odor:

I have a 100 year old house in NYC. I have a front crawlspace built with hollow building blocks and dirt floor,adjoining regular basement built with poured concrete, and a back crawlspace made adjoining basement with building blocks and dirt floor. The joists run from front crawl through basement to back crawl, so the crawls breathe into the basement. As spring and summer arrive i get musty smell that lingers until the fall. Once heating season arrives the smell starts. These have been my attempts to fix the problem. Easy Breathe fans (similar to wave or humidex) in each crawl space to remove musty air. 12 mil vapor barriers on the floor of each crawl space (but not tightly against the building block walls). Dehumidifier in basement and fans into each crawl space and then easy breate fans in both crawl spaces to expel musty air.

Possible solutions: Extend vapor barriers on crawl spaces floorsto within 2 inches of sill plates, but use polyurethane caulk to ensure the vapor barrier is tightly against wall and is not allowed to breathe into crawl space. Essentially trap the musty air under vapor barrier. 2. close off the air between crawls and basement. Not easy as each gap space is 8 inches by 23 feet.
I can't fit crawl space dehumidifiers into crawl space but I could purchase a heavy duty dehumidifier that I could hang from basement ceiling and vent directly into crawl space. I could add crawl space humidity detectors into each crawl space to indicate the humidity and try to keep that at 50% or below. I could possibly remove the fiberglass insulation int the crawl space ceiling but prefer not to bother. Not sure how to insulate the rim joists as floors above crawls are cold in winter. I don't thing I need french drains in crawls. The soil can be damp but I have never seen puddles of water.

I would love to hear replies from people who have had success. Thanks for listening and to any constructive advice.

By: David Butler

David Butler — Wed, 03 Sep 2014 07:34:28 +0000

@Matt, your situation raises
@Matt, your situation raises several questions and is too specific to get into details in a forum like this. Feel free to contact me privately if you're interested in professional guidance.

By: matt

matt — Wed, 03 Sep 2014 06:17:59 +0000

Hello,

Hello,

I have just bought a house with some crawl space issues. It's for the most part dry outside of extremely heavy rains. It does have plastic down with gravel. It's not overly moldy all the floor joist look great. Although it does have a Strong crawl space smell. hvac there is some trunk line that that is not insulated and does sweat. I'm in southern ohio. Also they added two supply ducts to the garage. When open the pressure obviously goes negative in the house and unleashes the crawl space smell the the house. I was planning on encapsulating the crawl. Adding a perimeter drain. Sealing and insulating duct. Insulating crawl walls. My next thought was to add a 6 inch supply and 6 inch return to the crawl. Controlling these with dampers and a Humidistat. My thought that running the return air through a filter UV light and over an evaporator coil would help with air quality over a transfer vent to the house? When the crawl was positve with pressure. The house currently has a furnace with with ecm motor that should compensate for change in duct pressure. (Carrier Infinity with 2 stage AC) any thoughts or insight would be great.