Check the listing for details. Felt 550™ - Under Vapor Barrier Protection. Condition: New. Listed at 129.17 USD. Felt550™ Has Two Significant Uses In A Crawl Space Puncture StrengthThe Felt550™ is made from virgin Polypropylene and woven into an lightweight and extremely puncture resistant material. There is no organic material used when making this product so it will naturally resist mold and mildew growth. In fact, the Felt550™ was designed and engineered to be in contact with water and the earth 100% of the time. Putting all of these features together makes it perfect to use under a crawl space liner or vapor barrier to protect it from sharp stones, rocks and other debris.Soil Gas MitigationCrawl spaces are harsh environments and with that comes considerations in air quality. One of the most serious is Radon Gas, because it is a killer. The Felt 550™ plays an important roll in Radon Gas Mitigation. The Felt 550™ creates an air gap between the vapor barrier and the soil, enhancing the results of the active Radon fan(s). Allowing the fans(s) to keep a negative pressure on all parts of the crawl space floor and eliminating any "pockets" that seep the gas into the space.The Felt 550™ also plays a key part in mitigating other soil gasses that cause odor. As we continue to do research on the best ways to fix the problems with air quality, energy loss and moisture levels we discover new problems and their solution. One of those new problems is soil gas odor(other than Radon Gas). This problem is not everywhere and it has nothing to do with our vapor barriers causing the smell (other plastics have been found to contribute depending on their makeup and additives). Like with Radon Gas, the Felt 550™ enhances the results of the fan to mitigate the odor.