Wraptite® converts property developer to benefits of external airtightness layer

The Scalby Road property features a 140mm timber stud, filled with insulation. To the outside of the stud is a sheathing board, another 50mm of rigid insulation, and the Wraptite membrane. The walls were then finished with cladding or a rendered board on battens.
The Wraptite membrane continued from the walls to the pitched roof, which was finished in a metal standing seam system. Wrapping the whole building –first in insulation, and then in Wraptite – helped to reduce thermal bridging and deliver a better standard of airtightness.
The membrane’s self-adhered backing makes it an excellent choice for a complete airtight envelope, as it also ensures resistance at laps against water penetration, dust, and air infiltration.
“With the walls and roof covered in Wraptite, the only areas with the potential for air leakage were the junction at the ground floor, and around the windows,” explained Chris.
Addressing the former simply meant ensuring the floor’s radon barrier continued up the external walls to lap with the Wraptite. To deal with the latter, Chris used Wraptite Liquid Flashing, supplied by the A. Proctor Group.
That meant the only penetrations through the external airtightness line were one cable and one water pipe. This is in stark contrast to an internal airtightness line, where it’s necessary to detail around floor joist ends, and where any socket box in the wall or downlighter in the ceiling is a penetration in the airtightness layer

Chris made the decision to experiment with an external airtightness line having seen various timber frame builders in North America advocate for it as a solution: “I follow a lot of them on YouTube, because they’re experienced in building this way and have already overcome a lot of the pitfalls.”
Having seen the potential benefits, Chris began researching the available options and settled on Wraptite. In particular, he was reassured by it being a Passivhaus-certified component.
Nevertheless, to prepare for every eventuality, Chris had the airtightness test carried out before internal finishing was complete – just in case he had to install any airtightness measures internally. He needn’t have worried.

“We normally do quite well with the internal airtightness line,” said Chris. “Trying really hard, we’ve consistently achieved results between 1.0 and 2.0 air changes per hour (ACH) at 50 Pascals pressure. On Scalby Road, using Wraptite for the first time, we achieved 0.35 ACH.”
In fact, so airtight was the dwelling as constructed, that when Rydale Testing set up the blower door test to measure the airtightness, it pulled the fan right out of the opening! The test had to be set up again with the fan mechanically fixed into the opening.
For Chris, the experience of changing approach to an external airtightness line was daunting at first, but the results speak for themselves: “It’s just about being educated, because doing the airtightness externally is actually so much easier. Wraptite simplifies everything and it’s a really impressive product. When we did the airtightness test and I saw the result, I was blown away.”
Find out more: https://proctorgroup.com/products/wraptite