The following thesis details an examination of radon and indoor environmental quality for low-income homes in Colorado Spring, Colorado. This investigation was completed in two parts: a field study and a modeling study. The main aim was to draw conclusions on the connection between weatherization and indoor radon concentration. Additionally, fine particulate matter (PM_2.5), total volatile organic compounds (TVOCs), and mold and moisture were investigated before and after weatherization. From the field study, it was determined that there is no connection between weatherization and radon, PM_2.5, TVOCs, and mold and moisture. Radon concentrations appears to vary by season, although a statistical analysis showed no significant difference. The modeling study suggests that indoor radon concentration will increase upon weatherization proportional to how much the building envelope is tightened, and that indoor radon concentration has the potential to reach an unsafe level upon weatherization. Future studies are required for verification.