FURTHER RESOURCES:In Green Basics: Blown-In or Loose-Fill Insulation Insulating Roofs, Walls, and FloorsIn Product Guide: Blown InsulationIn Community Forum: Dense-packed insulation Is dense-packed cellulose an air barrier?In Blogs: Cellulose Insulation Roofing and Siding Jobs Are Energy Retrofit OpportunitiesVideos: How to Install Rigid Foam Insulation Outside a House Superinsulating a Home With Rigid Foam Editor’s introduction: With energy prices rising again, many homeowners are planning energy-efficiency improvements to their homes. But most people are unsure of where to begin, and even seasoned builders don’t always know which priorities should rise to the top of the list. Betsy Pettit, an architect at Building Science Corporation , recommends starting where you can get the most bang for the buck.Step 3: Insulate your wallsTable of Contents:1. The Basement2. The Roof3. The Walls4. The Windows5. Mechanicals6. Appliances7. Renewable EnergyFilling empty wall cavities with cellulose is a cheap, easy, effective way to warm up an old house. Blowing insulation into existing wall cavities is an art, to be sure, but many contractors have been doing it for years. By checking the quality of the job with an infrared camera, an insulation contractor can verify that all voids have been filled.If the home’s existing siding is nearing the end of its useful life, it’s possible to install a thick layer of rigid foam on top of the existing sheathing at the same time that the siding is replaced.This article is adapted from Betsy Pettit’s Remodeling for Energy Efficiency in Fine Homebuilding magazine.