Roof Space Ventilation Building Regulations

In many pitched roofs a ventilation slot is built in along two opposite eaves so that air can flow across the roof space.

Roof space ventilation building regulations. Condensation encourages rot and mould growth. Ventilation is not required to a warm roof system which is where the insulation is placed above the joists or rafters. Attics must have a minimum of 1 square foot of ventilation openings for every 150 square feet of floor space. Minimum requirements bs 5250 sets out the minimum requirements for roof space ventilation.

The roof space isn t intended to be a storage area so if you do put items up there you. Isbn 978 1 85946 679 7 pdf 683kb this file may not be suitable for users of assistive technology. Around 25 per cent of heat loss occurs through a building s roof but high levels of insulation in historic roofs can be counter productive sometimes even accelerating heat loss in the long term. Jonathan taylor s article unpacks the key issues including the role of moisture ventilation and buffering.

The recommended ventilation ratio to provide for vented attic assemblies when an air barrier is present is the 1 300 ratio as specified by most building codes. Ventilation 2010 edition incorporating 2010 and 2013 amendments ref. Cold roofs versus warm roofs. 1 300 ventilation ratio recommended.

A roof void above an insulated ceiling. Both building regulations and nhbc require ventilation to be provided in roof spaces. Pitched roof spaces should have ventilation openings at eaves level to promote cross ventilation. When ventilating a roof the air should be able to enter at one end and travel through to the other end where it can exit.

The requirements will be met by the ventilation of those roofs where the moisture from the building can pass through the insulation. Otherwise ventilation is required and this is known as a cold roof system. For example in the average house with a cold loft there should be a minimum of a 7mm continuous ventilation gap at eaves when using a vapour permeable underlay with a normal unsealed ceiling. And current best practice.

Therefore it s important that the ventilation slots aren t blocked. If the attic is equipped with high and low ventilation openings the requirement is 1. The air gap dimensions shown on the drawings are the minimum widths required for clear continuous ventilation air paths at the eaves. Roof insulation thermal resistance at roof perimeter should be equal or greater to thermal resistance of exterior wall.

Roof space air quality 9 1 roof spaces with dampness problems such as from leaking roofs lid less water tanks moisture being vented into the roof space and moisture rising from the ground through building cavities require special attention. Contribute positively to moisture control in dwellings tending to be short of ventilation.