In a recent article in Environmental Building News (June 2008), author Tristan Korthals Altes informed us that having a working air barrier on the outside of a building could save as much as 30% off heating and cooling costs. I was quite surprised to find out how much of a difference an air barrier could make. I knew that air leaks in a building were not good, but did not realize that it costs so much in heating and cooling to compensate for them.
What is an air barrier?
An air barrier is any material that prevents outside air from getting in, and inside air from getting out. Possible materials include siding, sheetrock, roof felt, building paper, caulking, doors, and windows. Some of these materials are better than others at blocking the flow of air.
There are times when you may want air flow, so some of the materials are controllable, such as doors and windows. These aren’t a problem, most of the time (unless you forget that they are open). The problem comes from all the gaps and openings that you can’t see. That is where the money is at!
So, what is a building owner to do, knowing that money is flowing in and out of his building like the wind? The obvious answer is the block the flow of the air. However, that isn’t always so easy to do. First, you have to know where the air is leaking, then, how to stop it.
- Start with the most logical, and easiest, places first – around doors and windows.Check the seals and caulking on the outside. Look for gaps between the window frame and the building. These gaps can be caulked, but will require on-going maintenance as the caulk shrinks and expands with the weather. Check around doors to see if any light can be seen between the door and the frame. Add weatherstripping to any areas that aren’t tight. Also, adding a door sweep at the bottom of the door will stop drafts from below.
- Now check siding joints. Any place that two surfaces join each other on the outside of the building is a prime target for air infiltration. Check under the eaves as well. A quick squirt of caulk will take care of most of these, but again, maintenance is required.
- Up on the roof, check all flashings around protrusions. Make sure that they are sealed tightly. These may be more difficult to address if there are leaks here. If you don’t feel comfortable working with the roofing material, call an expert, especially on commercial buildings, where there may be a membrane roof.
In the article, Tristan Korthals Altes recommends that architects begin to create air barrier plans for their new buildings. This requires creating details for each problem area, as well as making site visits to check that the barrier materials are installed correctly before they are covered up.
I think this is a great idea whose time has come. So many times the contractor is left to fill in the blanks on how many of these materials are installed. With the potential savings of 30% in heating and cooling costs, the additional time spent designing and inspecting the system will be well worth it. With energy costs on the rise, no building owner wants to blow money away with a leaky building, especially when it can be prevented.
Resources (courtesy of Environmental Building News)
Environmental Building News – www.BuildingGreen.com
Air Barrier Association of America – www.airbarrier.org
Building Science Consulting (for common details of air barrier installation) – www.buildingscience.com