How To Ventilate Roof Space

In extremes of cold still air condensation overload may occur even where the roof space ventilation complies with the guidance given in bs 5250.

How to ventilate roof space.

These roof types are the most common type found in ireland. In older properties we must accept that air leakage happens and adequately ventilate the roof space to prevent harmful condensation forming. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. Fairly simple stuff fresh air in old stale air out.

The use of an exhaust vent in conjunction with an intake vent uses the natural forces of wind pressure and thermal effect collectively known as the stack effect to ventilate the attic space. Within this category of roof those where the ceiling follows the roof line and those where the ceiling is formed using ceiling joists. The first roof type to be discussed will be pitched roofs. In other words the entire vent opening doesn t count as vented space.

That said air resistance and interference such as vent grates reduces the area of true ventilation. Roof ventilation this picture represents what is considered to be the best way to ventilate a roof space. Intake vents located at the lowest part of the roof under the eaves allow cool. To ventilate a roof space adequately the type of roof structure must first be identified.

A double polypropylene cavity batten approximately 13 000 mm2 nfa fixed above every purlin can be used to ventilate the attic space up the roof slope but the actual air movement is very much dependent other factors of the building design. Place all the roof vents on the same side of the roof. If your roof peak runs parallel to the street put them on the backside where they ll be less prominent. Mark the roof venting locations from the attic where you can see the rafters and avoid placing roofing vents over them.

If the attic space is going to be conditioned either for living or mechanical purposes or if a home design calls for a vaulted ceiling provision r806 3 in the international residential code calls for the roof deck above the space to be vented continuously from the eave to the ridge. Too many people believe the importance of roof ventilation is to increase energy efficiency during the summer. Vent the roof deck. Ventilation can be accomplished using various products and techniques.

Exhaust vents which are located near or on the ridge line of the roof and allow air to leave the attic. Different forms of high and low level ventilation are used as well apart from the soffit vents and ridge vents pictured.