Inaccessible crawl space in mountains and rooms above garage
  • Doug Stoll
    6
    I have a potential client with a 1960 cabin over an inaccessible crawl space with a 1980 attached addition of a garage on slab and bedrooms above the garage. The Radon test in the bedroom above the crawl space are due Tue (not my test).
    I suggested ventilating the crawl with a vent on one side and a small fan across from it. The problem is winter, pulling cold air across, potentially freezing pipes, and making floor cold. I remember a heating system talked about in the old list serve? What are possible solutions?
    Also, I think the rooms above the garage should have been tested also because of Radon entry points around the garage slab and foundation. I suggested an iterative approach (if Radon above crawl is high), to vent crawl space first, then test above crawl and above garage. If above garage is still high, then do a subslab there.
    Any ideas, experiences? Thank you very much,

    Doug
    Evergreen Radon and Construction Services
    Fort Collins, CO
    Doug Stoll Options
  • Dick Kornbluth
    26
    The following procedure has worked for us under similar circumstances. I assume that if the crawl space is inaccessible, there are no atmospheric combustion appliance in it. If that is the case, another option is to seal the crawlspace and depressurize it with a fan mounted on the exterior. You do not need a large amount of depressurization, just a few pascals wrt the living space above. If you can include a continuous fan control and measure the pressure in the crawlspace wrt to the living space above you can tune the system to create the minimal amount of depressurization necessary to keep soil gases from the crawlspace from entering the living space. The key is to seal the crawlspace from the exterior and from the house, so any openings between the living space and the crawlspace that are accessible should be sealed.
    Dick Kornbluth Options
  • Robert Burns
    31
    Dick has good advice. We have set up a radon fan for the exhaust with a thermostat that turns it off if the temperature approaches freezing. It may be difficult to find a thermostat that goes below 40 degrees. There are manufacturers of crawl space ventilation fans that come equipped with temperature (and humidity) controls. You may be able to override the humidity control as you want the fan to keep running nomatter how dry it is.
    If I was confident that a lot of outside air was not going to enter the crawl space you would not need the thermostat.
    Robert Burns Options
  • Henri Boyea
    107
    Firstly, if there are pipes in the crawlspace, it needs to be MADE accessible. Sooner or later there will be a plumbing issue. (I once hand dug a basement for that very reason).
    Secondly, the living area above the garage should definitely be tested: the slab is a totally different dynamic than the crawlspace.
    Don't discount the possibility that the slab is the entire problem, and that nothing needs to be done with the crawlspace. This is a great time to use a sniffer to check the radon concentrations in all the different areas.
    An HRV may be a good choice depending on the layout and test results.
    Henri Boyea Options
  • Chrystine Kelley
    84
    Doug, you have gotten great advice from everyone. I would suggest testing the rooms above the garage before any mitigation decisions are made. Chrys
    Chrystine Kelley Options
  • Karen Ahearn
    6
    ↪Doug Stoll
    You
    Karen Ahearn Options
  • Karen Ahearn
    6
    You suggested that ventilation before and during the radon test?
    Karen Ahearn Options
  • Doug Stoll
    6
    All, thank you. Karen, the test (by others) came back at 12 above the crawl space. The crawl was not power ventilated. Rooms above the garage were not tested. (I'd like to get a clarification on testing in rooms above a garage and slabs on grade with basements in NOLA, I think protocols recommend it, but not required). I will push for testing rooms above garage now, get an idea of slab influence. I haven't visited the property, going by photos and realtor (a really good one), and I agree, there shouldn't be pipes in inaccessible crawl, but there may be limited access. I like temp controlled fan, but exhaust needs to be up and around eave? Thanks again, all.
    Doug Stoll Options
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