Jun 23 2005
Eternit Building Materials has launched three new ventilation products in its fibre cement slates portfolio to help specifiers and contractors meet Building Regulations for roofspace ventilation.
Approved Document F2 requires that all roofs insulated at ceiling level should be provided with ventilation openings at eaves level to promote cross ventilation. In addition, BS 5250 recommends the additional use of ridge ventilation to remove moist air from the roof apex.
In situations where there are valleys between eaves and ridge, pockets of stagnant air can occur because there is no direct air path between the two. This creates a condensation risk that is increased when the insulation follows the line of the rafters because the ventilation path is so restricted.
Eternit’s new ABS/PVCu valley ventilators for use with open lead-lined valleys can be fitted to the battens on each side of the valley, providing 5,000mm2/m free airspace per rafter void and eliminating the risk of condensation. Not only do they ventilate the whole valley, their ribbed bars provide a guide for cutting slates to the correct rake.
Secondly, to comply with the requirement for a free airspace of 5,000mm2/m at the ridge or at high level where insulation is fitted at rafter level, the voids between the rafters must be linked at high level to ensure the whole roofspace is ventilated.
Eternit’s new PVC cross-rafter ventilator provides a clear air path between the rafter voids in roofs where insulation is fitted at and above rafter level, reducing the number of slate ventilators required to comply with the Regulations and allowing air movement where there are obstructions such as dormers and hips.
And last but not least, Eternit’s new ventilated top abutment meets both the requirement to achieve a watertight seal between a mono pitch roof and a wall while ventilating the space below. It combines a 6m plastic ventilator with lead flashing to create the watertight seal on the top course of slates.