This study evaluated the effectiveness of current weatherization (Wx) practices and improved ground covers and other additional precautionary measures in avoiding increases in indoor radon. Energy improvements may reduce air exchange and outdoor air supply, and radon exposures could increase. This case-control study evaluated homes receiving Wx and compared the radon levels in weatherized homes (before and after Wx) to radon levels in control homes that received no treatment. Results show the measures succeeded in avoiding a statistically significant increase in radon levels on the first floor (p=0.78) and a marginally significant increase of about 0.8 pCi/l (p=0.06) in the basement after retrofit. These changes are lower than had been found in a previous study (Pigg et al., 2017) suggesting that Wx with precautionary measures can avoid living area increases in radon exposure.