Seal the envelope. Pay less to heat and cool it.

Heated and cooled air doesn't just leak through windows, it leaves through dozens of hidden gaps: the attic hatch, recessed-light cans, rim joists at the basement ceiling, plumbing and wiring penetrations, top plates above the walls. A blower-door test maps every leak. Crews seal them with caulk, foam, and weatherstripping. This single step typically cuts infiltration by 30 percent. Done first because insulation over a leaky envelope is money you light on fire.

With the leaks closed, the cavities get filled to current code: attic floor to R-49 or R-60, walls dense-packed to R-20 or better, basement rim joists and band joists treated as part of the same continuous envelope. Materials vary by assembly: blown cellulose for attics, dense-pack cellulose for walls, mineral wool or closed-cell foam where moisture matters. A typical whole-house retrofit takes two to four days, and the house holds temperature noticeably longer the same night.