Wraptite converts property developer to benefits of external airtightness layer

An experienced property developer has seen immediate benefits from using the A. Proctor Group’s Wraptite external air barrier solution. So good were the results of the airtightness testing at the property on Scalby Road in Scarborough that the testing company thought their equipment was broken and needed recalibrating! 

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 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 had the airtightness test carried out before internal finishing was complete – just in case he had to install any airtightness measures internally.  

“We normally do quite well with the internal airtightness line,” said Chris. “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 0.35ACH.” 

In fact, so airtight was the dwelling that when Rydale Testing set up the blower door test to measure the airtightness, it pulled the fan right out of the opening! The fan had to be mechanically fixed into the opening. 

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