The term "home energy audit" gets used for everything from a 20-minute walkthrough by a contractor who wants to sell you insulation to a full-day diagnostic assessment by a certified building analyst with $15,000 worth of test equipment. The word "audit" doesn't have a protected meaning in most states, which means you need to know what a real audit looks like before you book one.

I've been performing BPI-protocol energy audits for ten years. Here's what a thorough, diagnostic-grade assessment actually covers — and what questions to ask to make sure you're getting it.

Before the Auditor Arrives

A good auditor will ask you to gather 12 months of utility bills before the visit. This isn't busywork. The bill history provides the only objective measure of your home's actual energy consumption pattern — seasonal peaks, anomalous months, and baseline load. It also gives the auditor context for what they're likely to find before they walk through the door.

You should also be prepared to describe any comfort complaints you're experiencing: rooms that are hard to heat or cool, cold floors in winter, drafts near windows or outlets, humidity problems, odors from the crawl space or basement. These complaints often point directly to the problem areas before any testing begins.

The Building Walkthrough

The first phase of the audit is a visual inspection of the house — exterior, attic, basement or crawl space, and accessible wall and ceiling assemblies. The auditor is looking for:

This walkthrough takes 60 to 90 minutes in a typical house. An auditor who spends 15 minutes doing a walkthrough before proposing work hasn't actually evaluated your house.

The Diagnostic Testing Phase

The walkthrough tells the auditor what they can see. The diagnostic tests measure what they can't. A complete BPI-protocol audit includes:

Standard Diagnostic Tests

✓Blower door test — measures total building air leakage (CFM50 and ACH50) and, when combined with smoke pencils or thermal imaging, locates the dominant leakage pathways
✓Duct leakage test — measures total duct system leakage and, where conditions allow, leakage to outside; identifies whether duct losses are a significant driver of energy waste
✓Combustion safety assessment — CAZ depressurization test, spillage test at combustion appliances, CO measurement in flue gases
✓HVAC airflow and static pressure measurements — confirms the HVAC system is delivering air to each zone as designed and that static pressure is within equipment specs
✓Combustion analyzer check — measures efficiency and CO production of combustion appliances in steady-state operation

The difference that matters: An audit without a blower door test is a visual inspection, not a diagnostic audit. The blower door is the tool that makes air leakage measurable rather than guessable. If the contractor who offers you a "free audit" doesn't bring one, they're not auditing your house in any meaningful sense.

The Report

A complete audit ends with a written report that documents the test results, describes the specific problems found, prioritizes improvement recommendations based on estimated impact and cost, provides estimated savings for each recommended improvement, and notes any safety issues that require immediate attention.

The report should be specific to your house — not a generic template with a couple of fields filled in. If the recommended improvements are all the same as what the auditing contractor happens to sell, ask whether an independent auditor would produce a different list.

How to Find a Qualified Auditor

The most reliable credential to look for is BPI (Building Performance Institute) Certified Building Analyst. BPI certification requires completing accredited training, passing a written exam, and demonstrating field competency in blower door operation, combustion safety, and building envelope diagnostics. It is the closest thing the residential energy efficiency industry has to a professional standard for auditors.

RESNET HERS Raters are trained in a different but overlapping protocol, primarily used for new construction energy ratings but also valid for existing home assessments. State weatherization programs also train and certify auditors using similar protocols.

Your utility company is often a good starting point — many utilities maintain lists of approved contractors who meet their program standards, and some offer subsidized audits at reduced or no cost to customers. The DOE's Weatherization Assistance Program provides free audits and improvements to income-eligible homeowners through local agencies.

What the Tools on This Site Are — and Aren't

The calculators on EnergyWiseTools.com are designed to help you understand the relative impact of home energy improvements and develop an informed perspective before you talk to contractors. They are not a substitute for a real audit performed on your specific house.

Think of them as a way to ask better questions and understand the answers — so that when an auditor tells you your home has ACH50 of 12, you understand what that means and what to do with it. The value of a good audit is that it replaces guesswork with measurement. These tools can help you know what questions to ask in order to make that measurement count.