Building electrification is a key climate mitigation tool because fossil fuels used to heat, cool, and power buildings contribute more than 10% of U.S. energy-related greenhouse gas emissions. Efficient building electrification necessitates building envelope improvements, without which electricity demand will not only raise consumer costs but also require the buildout of additional electric grid infrastructure. To help avoid potential increased costs, policymakers and program implementers should focus on improving insulation in walls, attics, and basements, sealing air leaks, and installing higher-efficiency windows.