Where required, a builder may need to educate the designer, or vice versa, about air-barrier issues.Īn air barrier consists of materials assembled and joined together to prevent air leakage between the conditioned space and unconditioned space - or the inside and out.Ī typical air barrier incorporates more than a dozen materials, including some or all of the following: poured concrete sill seal wall sheathing housewrap contractor’s tape caulk spray foam gaskets window glass drywall polyethylene and weatherstripping. It’s common for some professionals to have a weak understanding of air barriers. It’s difficult for a builder to construct an effective air barrier if the designer doesn’t know where it’s located and how it will be built. But when building scientists talk about a home’s air barrier, they’re not talking about a single material they’re talking about a collection of materials that reaches from the basement slab, around the entire exterior of the building’s thermal envelope, and across the finished ceiling. Some products - for example, drywall, plastic, or housewrap - are considered air barriers. Often, the task of training tradespeople falls on the shoulders of the builder, who must be sure that everyone working on the building understands what an air barrier is. Materials that can accomplish a couple of the goals of an enclosure simplify the overall design.Ī well-designed air barrier requires cooperation from everyone on the job site. Green design looks for ways to combine an air barrier with an insulation layer. When the lines are uncertain, there’s a certain weak spot. When these lines aren’t clear, there’s a potential weak spot in the design. On conventional blueprints, it should be easy to draw a line around the part of a house that sheds water, but it’s not so easy to do so with the air barrier or thermal barrier (simple-shaped houses make this easier). Further complicating matters is the fact that these components don’t always line up - either literally or figuratively. The parts of the house where this balance is always the trickiest are where the roof meets the walls and the floor meets the foundation. Each part of the enclosure faces different challenges, but together they must achieve the same goals of stopping or slowing the flow of air, water, and heat while still allowing the inevitable intrusion of water a way to dry out. It extends out of the ground as aboveground walls, and it’s capped with a roof.
The enclosure begins in the ground with the foundation and floor. The building envelope, or shell, is the part of a house that you can draw a line around: the roof, the walls, and the floor.
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