- Roof space unventilated and sealed.
- Thermal insulation horizontal across ceiling.
- No ventilation to roof space required.
Benefits of Sealed Cold Roofs
- Energy efficient.
- Decreases air leakage / infiltration.
- Reduces condensation risk.
- Minimises the thermal bridge at the eaves.
- Negates the need for ventilation products.
- Lower installed cost.
- Cleaner roof void.
The sealed cold roof system does not need the provision of ventilation directly into the loft space and works on the principle of a Monarperm vapour open or permeable underlay being used under the roof tiles simply allowing vapour drive to diffuse any water vapour harmlessly into the batten space and the external atmosphere beyond.
The underlay should be draped as in traditional roof construction creating a minimum 10mm drape between the rafters. To achieve a truly sealed roof all laps in the underlay, all penetrations and all junctions should be sealed with Monotape.
When using a tight fitting covering such as imitation slates it may be necessary to provide an additional ventilated batten space above the membrane in which case the slate manufacturer’s guidance should be followed.
In this situation the underlay should be pulled taught across the rafters and secured using counter battens to create a deeper airspace under the slates / tiles which will aid drainage and improve the dispersion of water vapour.
The closed eaves should be packed tightly with mineral wool insulation eliminating thermal bridging.
To avoid water ponding behind the fascia and to prevent long term exposures of the underlay to ultra-violet radiation install Monarflex EavesGuard.
A well sealed Ceiling is required to control the transfer of water vapour into thee roof void and to achieve air tightness of the habitable space as required by Part L. To maximise the benefits of a sealed cold roof a vapour control layer should be considered directly above the internal ceiling.
Choose The Right Underlay
The following membrane types can typically be used: