The Many Benefits of Air Sealing
It’s common knowledge that a good chunk of our energy costs go into heating and cooling our homes. And after we’ve conditioned the air to be at just the right temperature throughout the house, it all too often leaks out through seams, cracks and even the tiniest holes. This is not only a waste of energy, but dollars. In fact, leaks account for the biggest losses in both categories.
We’ve long used insulation as a way to increase energy efficiency, but if air is leaking in and out, even the best insulation simply can’t do its job. That’s where air sealing comes into play. While it’s possible, and advisable, to air seal an existing structure, this blog focuses on creating an air-tight seal during the construction process. We’ve been doing it for a while now and are always discovering new processes, techniques and materials. For me, that type of “problem solving” is fun. I can get creative.
The first step in air sealing a home is to develop a strategy to seal what is basically a six-sided box, and there are tons of variables to consider. I start by looking at a cross-section of the plans and literally draw a red line where I think I can create an interrupted air-tight boundary. It’s important to recognize and address the most challenging spots or transitions. These occur where the walls meet the floor, between the floor and underneath the house and where the walls join the roof at the eaves.
Once we’ve achieved our air-tight boundary, we need to look at what are generally known as penetrations. These occur wherever there’s an opening, whether it’s for windows and doors, wiring, plumbing, cans for recessed lighting, electrical outlets and nail holes…anything that goes through the assemblies. We use a variety of materials including panels, tapes and membranes and liquid applied products, carefully sealing up the structure as we go along during the construction process. It’s much harder and much less cost effective to go back and try to plug leaks after the finishes are applied. Once the house is done, we use a number of tests to make sure we’ve caught everything. In the past few homes we’ve built, we passed the air leak tests on the first try. These tests generally involve pressurizing the house, then using an infrared camera and a smoke pencil to catch even the smallest leaks, especially those that can’t be detected by just feeling or looking for them.
The main types of air sealing products and systems we currently use include Zip Wall, SIGA tapes and membranes and Prosoco liquid applied materials. Each one has its own purpose and we use all three in a typical project. Zip Wall, which comes with its own proprietary tape, is not only an air barrier on the home’s exterior, it is also a moisture barrier. SIGA tapes and membranes are used to seal seams, transition points and penetrations. Prosoco is a good choice for sealing around windows and other openings. It’s easily applied by brushing it on like paint or from a caulking gun and flattened out with a putty knife.
Air-tight homes require mechanical ventilation—like the Zehnder Heat Recovery Ventilation unit we highlighted in our last blog and video—to ensure a supply of filtered, temperature-controlled air. We also take care to avoid use of products that contain toxins known as VOCs found in conventional paints, glues, carpets and other finishes. Fortunately, with current and upcoming changes in the building code, more materials and systems are coming on the market all the time.
Not only does a properly sealed home reduce energy consumptions and related costs, it has the added benefits of improving indoor air quality, comfort and durability. It’s just a better way to build.
Watch our video, Air Sealing for Efficiency.