After getting LEED certified, our builder gave us solid radon advice: test the soil before pouring the foundation and install a passive system with a vent pipe running up through the roof. They explained that even in low-risk areas, radon can seep in through slab gaps, so sealing all penetrations and using a vapor barrier underneath is crucial. We also added an electrical outlet in the attic to easily add a fan later if needed, making the whole setup future-proof without breaking the bank. LEED builder radon advice 9