- Roof space Ventilated and sealed.
- Thermal insulation following the rafter line.
- Ventilation to roof space required.
Benefits of Sealed Warm 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.
- Better use of space within the building.
- Ensures all services are within the heated environment.
- Eliminates large cool voids within the construction reducing thermal stress.
Eliminating traditional ventilation and the potential condensation risk associated with large voids of cool air make this the optimum pitched roof solution. With the potential of additional living space, a cathedral roof design or a conditioned roof void are rapidly becoming the preferred choice of pitched roof construction in the UK.
In a warm pitched roof construction the thermal Insulation is placed in the rafter line. The position of the Insulation can be wholly above or partially between and above the rafter; alternatively it can be positioned between the rafters or partially between and below the rafter.
If the insulation thickness only partially fills the rafter depth the vapour open / permeable underlay should be draped over the rafter in the traditional method. The underlay should not be allowed to touch the surface of the Insulation and a clear air space ensured between the membrane and insulation. Should the vapour permeable underlay be laid directly on top of the insulation in a fully supported situation it should be secured by counter battens to allow water to drain effectively across the membrane surface and from the roof.
To achieve a truly sealed roof all laps in the underlay, all penetrations and all junctions must be sealed with Monotape.
To avoid water ponding behind the fascia and to prevent long term exposures of the underlay to ultra-violet radiation install Monarflex EavesGuard.
A vapour control layer must be used directly above the internal ceiling to prevent water vapour entering the roof envelope and to achieve air tightness of the habitable space as required by Approved Document L Building Regulations 2006.
A sealed warm roof construction can also be achieved by creating a 50mm ventilated air gap between the surface of the insulation and the undertile lining to allow water vapour to be safely removed from the roof construction.
It is important that the undertile lining drape does not touch the insulation and a minimum 25mm unobstructed ventilation gap is maintained at this point.
Choose The Right Underlay
The following membrane types can typically be used: