What R-value should a house have?

What R-value a house should have is defined by climate zone, building component, and current energy codes, but as a general guide for a well-built modern house you should aim for attic R-49 to R-60, wall total R-20 to R-30 including continuous insulation, floor R-25 to R-30, and basement wall R-15 to R-20. The International Energy Conservation Code breaks the US into 8 climate zones, with zone 1 being hot Miami requiring attic R-30 to R-49, walls R-13, and zone 8 being Arctic Alaska requiring attic R-60, walls R-20 cavity plus R-10 continuous, and floors R-30. For a high-performance or net-zero house, many builders target attic R-60 to R-80, walls R-30 to R-40 double-stud or with exterior foam, and under-slab R-15 to R-20. However, R-value alone is insufficient, you also need comprehensive air sealing to less than 3 ACH50, proper ventilation, and control of thermal bridging. Simply adding R-value without air sealing and without addressing ducts in attics will not achieve comfort. The best practice is to meet code minimums for your zone and then invest in air sealing and duct sealing before adding extra R-value beyond R-60.