Section 7.2.9
Ventilation
Roofs shall have adequate precautions against condensation and cold temperatures, to provided adequate ventilation and to avoid condensation in roof voids. Pitched roofs that have insulation at ceiling level should be ventilated externally.
Bloor Homes roof ventilation detail RF601
The appropriate over fascia vent fixed to the fascia in accordance with the manufacturers instruction
Where open eave details are required it should be provided at the blocking out section between the rafters.
Fix timber between the rafters on top of the last masonry course and fix section of fascia.
Fascia should allow for an over fascia vent to be fixed to the fascia board below the cover ply.
Large rafter roll ventilation trays, sometimes referred to as “chocolate boxes”.
A minimum of 2 fixing per rafter.
Ensure rafter roll is not pulled too tightly as this will prevent sufficient ventilation entering the roof space.
Large rafter roll ventilation trays must extend to cover the whole cavity width to prevent insulation blocking the pathway.
Ensure the rafter roll extends far enough up the rafter so the pathway does not get blocked by the loft insulation.
Measure the thickness of insulation from the ceiling cord to check this is accurate.
150mm of insulation must be provided from the cavity barrier at the soffit and extend over the wall plate in accordance with RF 601 to prevent cold spots forming.
In all cases, high level ventilation must be provided.
When dry ridge systems are used, this is provided by ensuring there is a 5mm gap in the underlay at the ridge.
