Crawl Spaces in a building or house can be an issue to contend with when planning a radon mitigation. Some crawl spaces are cemented over during construction or even after. Others are left open, exposing gravel and sand fill, or simply the natural occurring dirt mix found during excavation. These open crawl spaces are the ones that can be problematic in the end result to radon mitigations. Crawl spaces typically fall outside of the main house or building drain-tile system, and footing area. They have their own footing area, and hence, separate earth gas penetrration that can cause a potential separate high radon area from the basement area.
At RMES, we feel that pre-testing the basement and main area of the house is important… as well as testing the open crawl space(s) and areas over these crawl spaces. This “baselines” all data before any mitigation work is done, and allows post-mitigation testing comparisons to be made. As a typical basement mitigation pulls on sub-slab areas typically 3'-6' deeper than a standard crawl space areas, about 80% of “typical” sub-slab depressurization style mitigations cure the basement… and crawl space areas of high radon levels. The other 20% still pose high radon entrance points, and are only cured my covering the open earth air-tight, and running a lateral from the main mitigation piping to the crawl space and through the air-tight tarp.
The best way to quote radon mitigations containing open earth areas is to provide step-by-step mitigation pricing relative to testing and results. Since 80% of open earth areas don’t need to be covered and mitigated to get all livable spaces in the house or building to safe levels, it shouldn’t be necessary to cover and mitigate these areas until they prove to still be high in radon after initial post-mitigation testing. It should be noted that there are no EPA/ASTM protocols directed at the “need” to cover open-earth crawl spaces. There are protocols on how to cover and mitigate crawl spaces if they prove to remain high after the initial sub-slab mitigation.