Then aim for about 1 sq.
Roof space ventilation building regulations.
Both building regulations and nhbc require ventilation to be provided in roof spaces.
The building regulations northern ireland 2000 regulation b2.
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.
Where the void is open eaves to eaves air flow is effective along the longer sides of the building.
In many pitched roofs a ventilation slot is built in along two opposite eaves so that air can flow across the roof space.
If not measure the size yourself.
Of vent for every 300 sq.
Otherwise ventilation is required and this is known as a cold roof system.
Pitched roof spaces should have ventilation openings at eaves level to promote cross ventilation.
25mm air gap 25 000mm m ventilation applications of building regulations pitched roof ceiling and insulation horizontal open roof void building regulations state.
The requirements will be met by the ventilation of those roofs where the moisture from the building can pass through the insulation.
B resistance to ground moisture and weather and c5.
Building codes vary.
In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq.
In of vent opening per 150 sq.
Isbn 978 1 85946 679 7 pdf 683kb this file may not be suitable for users of assistive technology.
2002 which deals comprehensively with the subject of condensation in dwellings.
A roof void above an insulated ceiling.
The roof space isn t intended to be a storage area so if you.
Roof space ventilation introduction building regulation approved document c2 refers to bs 5250.
The open area of a vent is sometimes listed on the roof air vent as nfva net free vent area.
Swish ventilators also meet the recommendations bs 5250.
The building code lets you reduce that by half under some conditions but more roof ventilation is usually better.
Throughout the balance of this digest the terms attic and roof will and can be used interchangeably.
Therefore it s important that the ventilation slots aren t blocked.
Roofs with a pitch of 15 or more.
Ventilation 2010 edition incorporating 2010 and 2013 amendments ref.