B resistance to ground moisture and weather and c5.
Roof space ventilation building regulations.
The british standard code of practice for control of condensation in buildings as a means of compliance with a general requirement that adequate provision be made to prevent excessive condensation in a roof or.
If not measure the size yourself.
The building code lets you reduce that by half under some conditions but more roof ventilation is usually better.
In cold climates the primary purpose of attic or roof ventilation is to maintain a cold roof temperature to control ice dams created by melting snow and to vent moisture that moves from the conditioned space to the attic ventilation acts to bypass the vapour barrier created by most roof.
The open area of a vent is sometimes listed on the roof air vent as nfva net free vent area.
Pitched roof spaces should have ventilation openings at eaves level to promote cross ventilation.
Roof space ventilation introduction building regulation approved document c2 refers to bs 5250.
Roofs with a pitch of 15 or more.
Swish ventilators also meet the recommendations bs 5250.
Ventilation 2010 edition incorporating 2010 and 2013 amendments ref.
Throughout the balance of this digest the terms attic and roof will and can be used interchangeably.
Both building regulations and nhbc require ventilation to be provided in roof spaces.
In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq.
As amended fitness of materials and workmanship c4.
Of vent for every 300 sq.
In many pitched roofs a ventilation slot is built in along two opposite eaves so that air can flow across the roof space.
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.
Where the void is open eaves to eaves air flow is effective along the longer sides of the building.
A roof void above an insulated ceiling.
2002 which deals comprehensively with the subject of condensation in dwellings.
Building codes vary.
The roof space isn t intended to be a storage area so if you.
Isbn 978 1 85946 679 7 pdf 683kb this file may not be suitable for users of assistive technology.
Then aim for about 1 sq.
In of vent opening per 150 sq.
Therefore it s important that the ventilation slots aren t blocked.
