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Home Energy Audits

A home energy audit is the first step to assess how much energy your home consumes, and to evaluate what measures you can take to make your home more energy-efficient.
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Blower Door Tests - A blower door is a powerful fan that mounts into the frame of an exterior door. The fan pulls air out of the house, lowering the air pressure inside. The higher outside air pressure then flows in through all unsealed cracks and openings. The auditors may use a smoke pencil to detect air leaks. These tests determine the air infiltration rate of a building. Several reasons for establishing the proper building tightness are: to reduce energy consumption due to air leakage; to avoid moisture condensation problems; to avoid uncomfortable drafts caused by cold air leaking in from the outdoors; and to make sure that the home's air quality is not too contaminated by indoor air pollution.

There are two types of blower doors: "calibrated" and "uncalibrated". It is important that auditors use a calibrated door. This type of blower door has several gauges that measure the amount of air pulled out of the house by the fan. Uncalibrated blower doors can only locate leaks in homes. They provide no method for determining the overall tightness of a building. The calibrated blower door's data allows the auditor to quantify the amount of air leakage and the effectiveness of any air-sealing job.

Thermographic Inspection - Energy auditors may also use thermography—infrared scanning—to detect thermal defects and air leakage in building envelopes. Thermography measures surface temperatures by using infrared video and still cameras. These tools see light that is in the heat spectrum. Images on the video or film record the temperature variations of the building's skin, ranging from white for warm regions to black for cooler areas. The resulting images help the auditor determine whether insulation is needed. They also serve as a quality control tool, to ensure that insulation has been installed correctly.

A thermographic inspection is either an interior or exterior survey. The auditor decides which method would give the best results under certain weather conditions. Interior scans are more common, because warm air escaping from a building does not always move through the walls in a straight line. Heat loss detected in one area of the outside wall might originate at some other location on the inside of the wall. Also, it is harder to detect temperature differences on the outside surface of the building during windy weather. Because of this, interior surveys are generally more accurate, as they benefit from reduced air movement. Thermographic scans are also commonly used with the blower door is running. The blower door helps exaggerate air leaking through defects in the building shell. Such air leaks appear as black streaks in the infrared camera's view finder.

Most energy audits take from four to eight hours and cost between $300 and $500. Any retrofit work would of course cost additional money.

Finding and Selecting an Energy Auditor - There are several places where you can locate professional energy auditing services. Your state or local government energy or weatherization office may help you identify a local company or organization that performs audits. They may also have information on how to do your own audit. Your electric or gas utility may conduct residential energy audits, or recommend local auditors. Also check your telephone directory under headings beginning with the word "Energy" for companies that perform residential energy audits. Another possibility is to contact the National Association of Energy Service Companies (NAESCO). NAESCO has member companies nationwide that specialize in energy audits for both large commercial buildings and homes. Contact NAESCO for information on which energy service companies are near you.

Before contracting with an energy auditing company, you should take the following steps:
  • Get at least five references, and contact all five. Ask if they were satisfied with the work.
  • Call the Better Business Bureau and ask about any complaints against the company.
  • Make sure the auditor uses a calibrated blower door.
  • Make sure they do thermographic inspections or contract another company to conduct one.

© 2004 U.S. Deptartment of Energy

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