A Note on Air Barriers
With the framing progress this week, we were able to snap a couple close up photos of the air barrier system – the part of the home that will help keep our house airtight, warm and healthy.
An effective air barrier should be:
- continuous across the building envelope
- air impermeable
- durable and designed to last the life of the building
- resistant to changes that might occur over that period e.g. thermal expansion or moisture absorption
Air barriers can be installed on the interior or exterior of a home. We’re working with an envelope engineer to dial this all in and using a suite of products made by German company @proclima_de, namely Solitex Mento 1000 and Intello Plus.
Mento 1000 is an exterior wind-sealing system that provides watertightness against rain, but also actively transports moisture to the outside. Intello Plus is what’s known as a ‘humidity-variable air tightness system’ that gets installed on the interior side of the insulation. This product literally changes molecular structure based on surrounding humidity! It protects the structure from condensation in the winter, and allows moisture to dry out in the summer.
Given the design of our house, with gable trusses and plywood shear walls spanning from floor to roof, we weren’t able to install a purely exterior air barrier that wraps around the top plates of the upper floor.
Instead, our project team has gone with an exterior air/vapour barrier (Mento 1000) at the basement level which wraps around the rim board and enters the house at the main floor in a continuous lap. Here, it connects to an interior air/vapour barrier (Intello Plus) that provides continuous coverage of the main floor walls up into the ceilings.
With our @chbanetzero energy target, we will need to meet air tightness metrics of <1.5 ACH @ 50 pa. Our mid-construction blower door test this spring should tell us how well we are tracking ☑️
Are there diminishing returns in energy savings for increasing air tightness? Is there such a thing as too airtight? Building scientists think not…
Air leakage is not only an important factor in energy modeling, but also a major contributor to indoor comfort, indoor air quality, and building structural integrity. That said, the tighter a home, the more critical it is to provide proper ventilation through other means, i.e. a fully distributed ventilation system. The BC Energy Step Code Handbook, Zero Emissions Building Exchange (ZEBx) and ProClima building science website are excellent resources for anyone wanting to dive into more details on all of this 🤓
#netzero #netzerohome #greenbuilding #sustainability #airtightness #airbarrier
