Today we have had a pre plaster air test, the result was 4.5 which leaves some room for improvement. The main areas of leakage were as follows;
- Through the electrical back boxes. We hope to remedy this by sealing the inside of the box with intumescent mastic. For future projects it would be better to use airtight back boxes.
- The junction between membrane and plaster in corners and around joists. This will be rectified with the use of the Orcon F mastic to form a better seal.
- All penetrations through the g/f membrane. More attention to detail around the pipes.
- Walls in general that are plastered and need patching, the air test engineer has stated that a continuous plaster covering as opposed to patching will be better for a lower result.
- The staples to the membrane although we have fixed them as specified would show a collective hole of approx 50mm when added together. To rectify this we will apply the Tescon No1 tape over the staples. (see photo)
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| Staples taped over on airtight membrane |
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| Ceiling membrane with tape applied over staples |
Installing the back-boxes within plaster would also be a way of providing an air-tight seal behind the back boxes.
ReplyDeleteIt's very interesting to find air escaping through the staples of the air-tight membrane. Very glad the air-test was carried out at this point - vital to identifying issues when still chance to rectify. Original air permeability test for the existing house was 10.44 m³/(h.m²), so already more than halved. Target is 1 air change per hour.......