Build Science™ 401 Episode 7 explores how a highly integrated floor and foundation system comes together in an off-site–built home. Matt Risinger and Steve Baczek walk through the use of precast Superior Walls, engineered open-web floor trusses, ZIP-R sheathing, drain-and-vent cavities, and layered air-sealing strategies to manage moisture, airflow, and heat in a challenging, cold, high-moisture site. They explain why certain materials, like closed-cell spray foam and a smart vapor retarder, are treated as secondary safeguards rather than primary control layers, while still adding durability and resilience over the long term. The discussion also highlights fire and sound control within floor assemblies, using mineral wool, like ROCKWOOL's Safe’n’Sound batts, to slow fire spread and improve acoustics in open-web truss systems. Matt and Steve reinforce that good building science is about thoughtful system integration, redundancy where it matters, and maintaining continuity at every transition to build safer, longer-lasting homes.