Ask ten homeowners what the term “energy audit” means and you might get ten different answers. Many are surprised to learn that it is a legally defined term, with building ­science–based, national standards that emphasize building durability, comfort, and air quality as much as they focus on ways to reduce energy usage.

A qualified energy auditor is an experienced, interdisciplinary building scientist. The most recognized certifications for home energy auditors include the Department of Energy’s Home Energy Rating System, for HERS rater certification, which focuses on new homes, and the Building Performance Association (BPI) certifications, which focus on performance diagnostics in existing homes. Both perspectives are valuable, because no matter how new a home is, the day after the certificate of occupancy is issued, it’s an existing home, with particular conditions based on its climate zone, site, builder and subcontractors, owners, occupants, weather patterns, and more. For this reason, every energy audit will yield different recommendations.

The result of a comprehensive energy audit is a road map for the homeowner, and recommendations are not limited to energy efficiency. They may also include corresponding indoor air quality improvements, suggestions for air monitors, projected dates for major equipment or appliance replacement, and coordination with other relevant home improvement projects.

Energy efficiency upgrades are typically assigned a return on investment because the avoided cost of future energy use can pay for the improvements over time (they may be offset by available incentives or tax credits as well).

At my Roanoke, Va., building science firm, Better Building Works, we also include a best-fit feasibility analysis for renewable energy, electrification, and electric vehicle charging, as well as a net-zero-energy plan, in our audits. In this article I will show what a comprehensive energy audit looks like for two different homes, and how…