 |
|
|
|
 |
This most modern type of roof has only become possible through the recent introduction of breather roofing membranes with superior vapour permeability such as a performance leaders like Permavent, Permavent-MAX & Permavent-ECO. Although cold non–vented is not the best performing type of roof as recent changes to part L1 of the building regulations, requiring increased levels of insulation, have made it the most cost efficient against performance. |
By eliminating active ventilation the roof space it is therefore 25% more thermally co–efficient requiring less insulation. The only problem with this type of roof is that it will only work effectively when installed as a complete system using good working practice.
A cold non–vented roof requires that the roof space is isolated from all but residual amounts of vapour by means of a vapour control barrier from non–permeable sheeting such as Permavent–DRY. The use of this control barrier, fixed to the joists for example behind the plasterboard, will prevent the ingress of vapour through the ceiling.
Permavent should be laid on the roof in conjunction with a counter–batten to allow eaves to ridge ventilation over the top. The laps and peripheral edges of Permavent must be stuck and sealed using Permavent-TAPE (double sided butyl based tape). The type and style of insulation may vary quite considerably and all manufacturers will supply relevant information in accordance with the latest building regulations.
)
