Preparing for an Energy Audit
Prior to the home energy audit, make a list of any existing problems, such as condensation and uncomfortable or drafty rooms. Have copies or a summary of the home's yearly energy bills. (Your local utility can get these for you.) Our auditors use this information to establish what to look for during the audit.
Typically, we first examine the outside of your home to determine the size of the house and its features (i.e., wall area, number and size of windows). We then analyze your behavior:
• Is anyone home during working hours?
• What is the average thermostat setting for summer and winter?
• How many people live here?
• Is every room in use?
Your answers help us uncover some simple ways to reduce your household's energy consumption. If possible, walk through your home with the auditors as they work and ask questions.
The time and equipment used is determined by the type of audit you have requested. There are a range of options including a complete audit which includes the use of a blower door and infrared camera. The results are presented in a comprehensive written report which includes photographs. Another option is thermal camera imaging, which just includes photographs in the report.
Blower Door Tests
A professional audit includes the use of a blower door. The reason for this is that up to half of the energy loss is due to air leakage. We use blower door tests to help determine a home's air tightness.
Sources of air leakage include:
Plumbing Penetrations 13%
Electric Outlets 2%
Floors, Walls & Ceilings 31%
Fans & Vents 4%
These are some reasons for establishing the proper building tightness:
Reducing energy consumption due to air leakage
Avoiding moisture condensation problems
Avoiding uncomfortable drafts caused by cold air leaking in from the outdoors
The blower door is mounted into the frame of an existing 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. Our auditors may use a smoke pencil to detect air leaks. These tests determine the air infiltration rate of a building.
A blower door consists of a frame and flexible panel that is placed in a doorway, a variable-speed fan, a pressure gauge to measure the pressure differences inside and outside the home, and an airflow manometer and hoses for measuring airflow.
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.
Take the following steps to prepare your home for a blower door test:
• Close windows and open interior doors
• Turn down the thermostats on heaters and water heaters
• Cover ash in wood stoves and fireplaces with damp newspapers
• Shut fireplace dampers, fireplace doors, and wood stove air intakes.
We use an infrared camera to detect thermal defects and air leakage in building envelopes. The camera measures surface temperatures by seeing the light that is in the heat spectrum. The camera senses temperature variations of the building's skin, ranging from white for warm regions to black for cooler areas. The resulting images help our auditor to determine whether insulation is needed. The images also serve as a quality control tool, to ensure that insulation has been installed correctly.
An infrared inspection is either an interior or exterior survey. Our energy auditors decide 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 difficulty, interior surveys are generally more accurate because they benefit from reduced air movement.
The infrared scan is commonly used with a blower door test 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 viewfinder.
Infrared scanning allows our energy auditors to check the effectiveness of insulation in a building's construction. The resulting images help our auditors determine whether your home needs insulation and where in the building it should go. Because wet insulation conducts heat faster than dry insulation, infrared scans of roofs can often detect roof leaks.
The energy auditor uses an infrared camera which is the most accurate thermographic inspection device. It produces a 2-dimensional thermal picture of an area showing heat leakage. Spot radiometers and thermal line scanners do not provide the necessary detail for a complete home energy audit. Infrared film used in a conventional camera is not sensitive enough to detect heat loss.
To prepare for an interior thermal scan, the homeowner should take steps to ensure an accurate result. This may include moving furniture away from exterior walls and removing drapes. The most accurate thermographic images usually occur when there is a large temperature difference (at least 20°F [14°C]) between inside and outside air temperatures.
In addition to using an infrared camera during an energy audit, you should have a scan done before purchasing a house; even new houses can have defects in their thermal envelopes.