Vapour Barrier Insulation Explained

The build-up of a warm flat roof starts with a good vapour barrier followed by insulation then more decking or just the roofing materials depending on if you want the roof soft or solid.

Just what vapour barrier to use is not that clear. Is the silver foil to the back of the insulation OK to use for the vapour barrier? Is a sheet of plastic OK?

Go to some manufacturers websites and they will have several different vapour barriers. Unfortunately the answer is “depends on your roof and your property” calculations should be undertaken for each and every project, if not then the better the vapour barrier is, the more chances of it being correct.

Warm Flat Roof Vapour Barrier Details

The detailing of the warm roof is very important if gaps in the insulation are left cold bridging can occur and potentially sweating could happen. Warm roof technology is still evolving so; please make sure your roofer understands what they are doing. We find that we get lots of phone calls from the property owners explaining that their roofer has installed a warm roof with ventilation is this correct? NO.

If you have any questions regarding your vapour barrier or VCL, then feel free to leave a comment below or contact us and we will respond promptly.