Cross Flow Ventilation Flat Roof

Flat roofing requires a different type of vent then standard angled roofs.

Cross flow ventilation flat roof. To help disperse the moisture vapour the building regulations require cross ventilation to be provided in the form of a 50mm air gap between the deck and the insulation and continuous gap of about 25mm at the eaves. In a concrete deck for example this gap could be created by fixing 50x50mm timber battens at 600mm centres and attaching the insulation to underside of these battens. Ventilation for cold roofs. Even if you have a small shed you should allow for a proper vent to keep the air fresher in the space.

Consisting of acfoam ii or acfoam iii polyisocyanurate polyiso insulation board and a min. Duo pitch roofs greater than 20 0 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. Taking advantage of this natural process referred to as passive ventilation is the most common way to vent an attic. Additionally if the span is greater than 10m the overall ventilation area should be increased to at least 0 6 of the total roof area.

We have large overhanging soffits and have a continious ventilation grill running all the way around thats how the buzzing stripey things got in to nest. Hot air exhaust vents located at the peak of the roof allow hot air to escape. 19 32 cdx plywood separated with and bonded to 5 individual 1 0 1 5 or 2 0 vent spacer strips. When thermal insulation is placed below the deck the ventilation must also be on the underside.

Roof spaces should have ventilation openings in two opposite sides to promote cross ventilation. Cold roof definately needs ventilating. Acfoam crossvent is offered in a variety of composite thicknesses providing long term thermal resistance lttr values from 5 7 to 23 6. 2011 code of practice for control of condensation in buildings stipulates that there should be a ventilation gap between the insulation and the bottom of the flat roof deck of at least 50mm.

Thermally efficient cross ventilated non structural composite insulation. Mbc provided us with a flat deck and then we built another shaped roof on top to meet our design planning requirements. Roof with a pitch of less than 15 and those where the ceiling follows the pitch of the roof. 7 16 apa teco rated osb or min.