Finding and Sealing Air Leaks in Your Building’s Envelope

Air leaks in your building’s envelope are probably the most common, and most costly, of the sources of energy waste. Adding to the problem is the fact that air leaks can sometimes be very difficult to find, which means many such leaks go undetected and continue costing you money throughout the year. Finding and sealing these air leaks will pay off in multiple benefits, including less wasted energy, lower heating and cooling costs, and more consistent indoor temperatures. Here is a brief guide to finding and sealing air leaks in your commercial building.

What is the Envelope?

The envelope of your commercial building is the walls, windows, doors, ceilings, foundations, and roofs that create the barrier between indoor and outdoor spaces. Much like an envelope you receive in the mail contains papers, the envelope of your commercial building contains the indoor spaces and protects them from the effects of the outdoor environment. Inside this envelope, you use your HVAC system to keep the space warm in the winter and cool in the summer. Any openings in the envelope will have a significant effect on the temperatures inside the building.

Common Sources of Air Leaks

There are several sources of expected air loss in your building’s envelope. Doors, for example, are areas where some indoor air will get out and outdoor air will get in as customers and employees come and go. However, there are other common sources of air leaks that should not allow conditioned air to escape or seasonal outside air to enter. These include:

• Around door and window frames and casings.
• Around glass panes in windows and doors.
• Areas where pipes, wires, conduits, or chimneys penetrate the walls or ceilings.
• Spots where the foundation or attic floor contact the building’s frame.
• Electric outlets and switches.
• Ventilation fans in the wall or ceiling.
• Areas that have obvious holes, cracks, or gaps in the building’s structure.
• HVAC system ductwork, where sections are loose or damaged and connections aren’t properly sealed.

Finding Air Leaks

There are several effective techniques for finding air leaks in your commercial building’s envelope. They include:

• Visual inspection, looking for any visible openings in the envelope.
• Physical inspection, feeling for drafts, cold spots, or inconsistent temperatures.
• Energy audits that include professional testing techniques. These include infiltrometer tests, also known as blower door tests, that pressurize the inside of the building and reveal the locations of even small, hidden air leaks. Smoke pencils emit a thin, steady stream of smoke that will waver noticeably in the presence of drafts or air leaks. Thermographic scans and infrared photography can reveal where energy is being lost through the walls and envelope of your building.

Sealing Air Leaks

Sealing air leaks is often a relatively easy process once the leaks are found. Some of the most effective sealing techniques include:

• Caulking around window and door frames and casings. This is usually done with silicone caulk that dries to form an airtight seal.
• Caulking around glass panes in windows and doors with clear silicone caulk.
• Sealing areas around wall and ceiling penetrations. For smaller areas, this can be done with caulk. Larger areas might require that insulation or other material be fitted into the openings. Spray-foam insulation is effective for sealing medium-sized holes and gaps.
• Sealing or caulking around electrical outlets and switches.
• Making sure HVAC ductwork sections fit together tightly and that connections are sealed with mastic or metal tape to stop leaks.
• Placing foam or rubber weatherstripping around windows and doors to seal gaps.
• Applying rubber sweeps or other material to stop drafts at the bottoms of doors.

Our goal is to help educate our customers about Plumbing, HVACR, Fire Protection, and Alarm Systems in Mechanical, Commercial, and Residential settings. For more information on finding and sealing air leaks in your building’s envelope, and to view projects we’ve worked on, visit our website!

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