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Crawl Space – Radon Mitigation & Insulation with Spray Foam or Polyurea?

MikeNH | Posted in General Questions on

We have a roughly 750sq/ft crawl space, 30×25. The only space above it is a bedroom and in the winter (climate zone 5) our radon levels rise to 4-6 and keeping the room warm is a challenge. The other part of our house is a standard basement that is basically sealed off from the crawl space. So there are two main objectives I am looking to solve, 1 – better insulation and 2 – reduce radon levels.

Insulation – The crawl space in has poured foundation walls and a poured floor with the only insulation being in the floor rafters, R19 batts. The batt install was done crappy, plenty of gaps and the ridge/sill areas either missing or falling out insulation.  

Radon – There is no mitigation in place today. 

After some reading and consulting with a insulation ‘expert’ I have come up with some options that I wanted to bounce off of others.

Option 1 – Spray closed cell foam the sill/ridge, walls @ 2-3″ and then the floor with 1-2″. PROS – This would address the radon I believe and improve overall insulation. CONS – Expensive

Option 2 – Spray the closed cell foam on the sill/ridge and walls but use a Polyurea type product for the floor. PROS – Improve radon mitigation but I was unable to find a real-life review of using Polyurea product to address radon. CONS – Insulation levels not as good as option 1.


With both of these options I was planning to do a ‘wait and see’ related to radon levels and if needed then put in an active system, hole in the floor piped out though I have recently read some threads of just using an inline fan out the side with a new make up air entrance. 


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