When our clients come to us they often have three priorities for their new home: they wanted it to be healthy, comfortable, and efficient.
At Clay Construction, those goals start with the building envelope. One of the most important factors in creating a high-performance home is controlling air leakage. The less uncontrolled air movement through the building envelope, the better the home’s comfort, energy efficiency, and indoor air quality.
On our Delta project, we achieved an impressive airtightness result of 0.48 air changes per hour (ACH). So how did we do it?
Building a Better Air Control Layer
Many builders use interior polyethylene (poly) as their primary air control layer. While this approach can be effective, it often requires numerous penetrations for electrical, plumbing, and mechanical systems.
Every penetration creates a potential weak point in the air barrier.
Instead, we chose to place our air control layer on the exterior of the building. By locating it outside the structure, there are significantly fewer penetrations to manage, making it easier to maintain a continuous and effective air barrier.
The result is improved airtightness and better overall building performance.
Why We Use a Self-Adhered Membrane
The second key decision was our choice of membrane.
For this project, we used SIGA Majvest 500 SA, with “SA” standing for self-adhered.
Most weather-resistant membranes require mechanical fastening using staples or screws. Every mechanical fastener creates a hole in the membrane, which can become a pathway for unwanted air leakage.
With traditional mechanically fastened membranes, air can potentially find its way through these penetrations, making it more difficult to achieve exceptional airtightness levels.
The Advantage of Self-Adhered Technology
A self-adhered membrane works differently.
When fasteners penetrate the membrane, the adhesive material seals tightly around the fastener. This creates a much more reliable air barrier and helps maintain continuity throughout the building envelope.
By minimizing leakage points and improving the integrity of the air control layer, self-adhered membranes contribute significantly to overall building performance.
Why Airtightness Matters
Airtight homes provide several important benefits for homeowners:
- Improved energy efficiency
- Greater indoor comfort
- Better control of moisture and condensation
- Reduced drafts
- Enhanced indoor air quality
Achieving low ACH numbers isn’t simply about meeting performance targets. It’s about creating healthier and more comfortable homes for the people who live in them.
The Result: 0.48 ACH
By placing the air control layer on the exterior and using a self-adhered membrane system, we achieved an airtightness result of 0.48 ACH.
For our clients, that’s a win.
It’s another example of how thoughtful building science and attention to detail can create homes that perform better for years to come.
— Larry Clay
The Clay Way
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