Sealing Inaccessible Crawlspaces

We are using radon mitigation systems to address a VOC vapor intrusion issue at multiple homes in a residential neighborhood. Many of the homes have multiple foundation types including inaccessible crawlspaces. Our approach for installing a mitigation system for the inaccessible crawlspace portion of these homes was to seal the perimeter block foundation and seal penetrations from the crawlspace to the first floor. We would then insert a 4" PVC pipe into the sealed crawlspace area and use a radon mitigation fan to remove air from this area.

We have received multiple complaints from homeowners that the recently installed mitigation systems are causing their homes to be cooler. The current approach for mitigating inaccessible crawlspaces may draw conditioned indoor air from the home.

We would like to come up with a way to seal inaccessible crawlspaces similar to our method of sealing accessible crawlspaces (i.e., use poly sheeting across the crawlspace floor, seal the poly sheeting to the perimeter of the crawlspace with caulk and/or bond tape, and use a poly flex drain to remove vapors below the poly sheeting) and in a way that would minimize drawing conditioned indoor air into the crawlspace (address the coolness complaint).

So far, we have the following ideas:

• Use rods to push poly sheeting back into crawlspace and insert poly flex drain under sheeting. Use expanding foam to semi-seal and insulate the crawlspace above the poly sheeting. A draw back to this approach is that we cannot guarantee the crawlspace has been sealed. Please feel free to offer insight for how we could modify this approach to acheive a good seal.

• Remove floor above crawlspace to provide access so that standard sealing approach could be implemented. This approach is costly and would disturb the residents. We would like to avoid this approach.

Any other ideas would be greatly appreciated!

Thanks,

Carolyn