Air Sealing – The Unseen but Crucial Element

While there are many exciting technologies and materials being used in Canada’s Greenest Home, one of the most important aspects of the home’s energy performance is taking care of air sealing details.

A lot of the heating and cooling energy that is lost from a home is not due to poor insulation, but rather due to air leakage between the inside and the outside. A very well insulated home will not perform well at all if a lot of air can transfer through the building enclosure.

A house is full of seams between different components and materials. At each interface, our team is being thoughtful and careful to ensure that the opportunities for air leakage are minimized. If we do well, we’ll hit the Passive House standard for air tightness of 0.6 AC/H (air changes per hour) at 50Pa (Pascals, the pressure difference between inside and outside during air tightness testing). Our current building code requires a minimum of 3.0 AC/H.

Straw bale walls are well known to have excellent insulative properties, but many straw bale homes are also very leaky at the seams where the plaster meets the ceiling, windows, doors and floors. Through the use of continuous barriers that run behind the plaster at the edges of each bale and tie into barriers at the ceiling, floor and doors and windows, we’ll keep these leaky areas in check.

For example, the bottom plates of our NatureBuilt prefab bale walls feature an air control membrane that is embedded under the plaster skin and extends over the wooden bottom plate. Our air barrier membrane from the foundation ties in behind the barrier from the wall, and the two are taped together at the seam. The baseboard trim will protect this junction from damage.

It’s slow, time-consuming work to ensure that each and every seam is cared for in this way, but it’s a key part of making a home as energy efficient as possible.

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