Roof Space Ventilation Building Regulations

Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.

Roof space ventilation building regulations.

Condensation encourages rot and mould growth. Duo pitch roofs greater than 200 pitch or greater than 10m span should have additional ventilation at the ridge to assist airflow through the roof void equivalent to at least a 3 mm wide continuous gap. The roof space isn t intended to be a storage area so if you do put items up there you. And current best practice.

Therefore it s important that the ventilation slots aren t blocked. The open area of a vent is sometimes listed on the roof air vent as nfva net free vent area. 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. Jonathan taylor s article unpacks the key issues including the role of moisture ventilation and buffering.

Most building codes require a ratio of 1 150 ventilation space to attic floor space. Roof voids must be ventilated in order to stop warm air condensing on cold surfaces. If the attic is equipped with high and low ventilation openings the requirement is 1. Isbn 978 1 85946 679 7 pdf 683kb this file may not be suitable for users of assistive technology.

Both building regulations and nhbc require ventilation to be provided in roof spaces. Ventilation is not required to a warm roof system which is where the insulation is placed above the joists or rafters. 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. Otherwise ventilation is required and this is known as a cold roof system.

The air gap dimensions shown on the drawings are the minimum widths required for clear continuous ventilation air paths at the eaves. You can also contact your local municipality to check on building code in your area. Attics must have a minimum of 1 square foot of ventilation openings for every 150 square feet of floor space. In of vent opening per 150 sq.

Cold roof with impermeable hr underlay if a building is 10 metres wide or more or the roof pitch 35 degrees or above then 10mm eaves ventilation is required together with 5mm ridge ventilation. Then aim for about 1 sq. 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. 1 300 ventilation ratio recommended.

If not measure the size yourself. Ventilation 2010 edition incorporating 2010 and 2013 amendments ref. Roof insulation thermal resistance at roof perimeter should be equal or greater to thermal resistance of exterior wall. Cold roofs versus warm roofs.