The Blower Door: Why It’s a Key Component of Your Home Energy Audit

A blower door test tells you something about your home you’ve always wanted to know: Exactly how much air it leaks.

Okay, maybe that’s not what you’ve always wondered. Still, infiltration of outdoor air into the home during summer and loss of heated air in winter are major sources of energy inefficiency. Sealing the leaks and closing the gaps that allow air exchange with the outside are the simplest, low-tech methods of realizing immediate efficiency gains in your home. Before you can do it, however, you need to know the extent of air leakage from the house and pinpoint the location of these hidden energy-wasters. That’s where a blower door test conducted by a trained professional technician comes in.

Why you need it
If you had a 3-foot by 3-foot hole in an exterior wall, you’d take immediate steps to close it in order to conserve energy and preserve interior comfort, wouldn’t you? Yet, in some houses, the cumulative total of innumerable tiny leaks can be the equivalent of a single opening that large. The problem is, all these inconspicuous leaks are a lot harder to quantify and locate than one big one. Sure, you can apply DIY methods, feeling for drafts and looking for obvious openings, and successfully identify some of the main suspects. However, it takes the technology of a blower door test combined with the expertise of an HVAC professional to reveal the true state of your home’s airtightness, calculate the total amount of air leakage and provide an efficient method of pinpointing the location of leaks.

How it works
A trained technician performing a professional energy evaluation on your home will come prepared to conduct a comprehensive, room-by-room survey. He or she will look at the makeup of windows and doors, the amount and quality of insulation, the condition of HVAC ductwork, the orientation of the structure and even information about the number of occupants and level of daily activity. In addition, the auditor will use specialized equipment to assess several critical factors influencing efficiency. Here’s what’s involved in the blower door phase:

1. A blower door is temporarily mounted in the frame of an exterior door. This door incorporates a powerful blower fan and sensors to detect the air pressure in the house as well as measure airflow through the fan. These sensors are linked to a computer programmed with the square footage and other data specific to your home.
2. All windows and exterior doors are shut. Vents are sealed and the fireplace flue and any other openings are verified to be closed.
3. When the blower energizes, air is drawn out of the home inducing negative air pressure in the interior. With the inside of the home at a lower pressure than outdoors, outside air begins streaming into the structure through all leaks.
4. The computer monitors the blower as it reaches a predetermined negative pressure level. At the same time, the airflow sensor measures the amount of air passing through the blower necessary to maintain that pressure level. With that information, plus data about the size of the house, the computer calculates an estimate of the cumulative size of all leaks combined, expressed in square inches.
5. While the home is in a negative pressure state and air is infiltrating through cracks and gaps, the technician can use a variety of methods to identify and mark the location of leaks. Utilizing a smoke pen, he or she can detect invisible air currents around doors and windows that indicate leakage. The technician may also use a thermographic infrared camera to image heat energy flowing in through leaks.

After the test is finished, you’ll receive a written report quantifying the amount of air leakage and other energy-wasting shortfalls in your home. Your HVAC contractor can suggest specific repairs—including sealing the identified leaks with caulking and weatherstripping—and other improvements to improve your household efficiency profile and give you an estimate of the cost. In most cases, a contractor can also provide a ballpark figure of how long it will take energy savings from the suggested improvements to pay for the cost of the work. The homeowner is not obligated to make any suggested repairs after an energy evaluation conducted by a reputable HVAC professional.

In Mount Pleasant and Titus County, our 56-year track record of HVAC sales and service makes Wood Air Conditioning & Plumbing the first choice for cooling and heating expertise. Contact us about scheduling a blower door test to reveal your home’s hidden leaks and keep you cooler and more efficient this summer.