Ventilated Cold Pitched Roof Construction

2002 using proprietary eaves and ridge ventilation fixed in accordance with manufacturers instructions.

Ventilated cold pitched roof construction.

If you live in an old building you may find that your roofing underlay is sarking felt if so you will need to allow for a 50 mm area of. Condensation encourages rot and mould growth. This removes the need for ventilation in the insulation a benefit that is particularly important with cold pitched roof construction. This traditional roof construction uses movement of air through the roof void to prevent the occurrence of harmful condensation.

However where vapour permeable underlays are specified this requirement may be relaxed. The minimum requirements for cold roof ventilation are set out in bs 5250 control of condensation in buildings which takes into consideration span pitch and roof area. In the cold pitched roof method of construction glass mineral wool insulation is placed at ceiling level between and over the ceiling joists. Ventilation at the eaves roof voids must be ventilated in order to stop warm air condensing on cold surfaces.

Cold roof voids are typically required to be ventilated. However where vapour permeable or low resistance lr. Inclined along the line of rafters warm roof or positioned within the roof structure to form an insulated void room in roof which can result in warm and cold roof areas. It can be inclined above between or below the rafters forming a warm or hybrid roof or positioned in the roof structure in different ways where a room in roof is to be created that can result in warm and cold roof construction types.

Cold pitched roofs can be ventilated or unventilated requiring the use of vapour impermeable and vapour permeable underlays respectively. This type of insulation system can be ventilated or not ventilated. In pitched roof construction thermal insulation can be placed horizontally at ceiling level cold roof. In pitched roof construction the insulation can be placed horizontally above the ceiling level forming a cold roof.

Where the ceiling follows the slope of a roof regardless of pitch or where a cold roof has a pitch less than 15 ventilation equivalent to a 25mm slot running the full length of the eaves should be provided a nominal clearance of 50mm should be maintained between the insulation and the roof underlay. Cold roof voids are generally always required to be ventilated. No ventilation is required for these types of roofs. A non ventilated tyvek system will not only prevent excessive condensation but offer substantial gains in energy efficiency.

A warm deck roof is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation. A cold pitched roof is where the insulation is placed either between or between and under the rafters or at ceiling joist level. The air gap dimensions shown on the drawings are the minimum widths required for clear continuous ventilation air paths at the eaves. Ventilation of the roof void should be provided in accordance with bs 5534 bs 5250.