Use the required equivalent or free area, duct size and wall thickness. Follow the ventilation design rather than measuring the grille face.
Background Air Inlets for Rooms and Solid Walls
A wall vent creates a defined path for air through the building envelope. MacBlair stocks vents for projects needing background or permanent airflow, with the internal grille, wall sleeve and external face selected around the opening and exposure.
Choose by required equivalent or free area, wall thickness and duct size. A large decorative grille can still restrict airflow, so use declared performance rather than face dimensions. External terminals should resist driven rain and include insect protection without being placed beside pollution or exhaust sources.
Seal the sleeve to the wall layers without filling the airway. Coordinate surrounding cavity wall insulation and internal insulated lining to reduce cold edges. Where a ducted appliance is connected, use the correct terminal rather than a passive vent, and review the wider building materials detail.
Wall Vents FAQ's
It may provide background ventilation when its declared equivalent area and position meet the applicable requirements. Check the complete ventilation design.
Passive vents move outside air by design. Correct sizing, controllable grilles where permitted and careful positioning can limit discomfort without blocking required airflow.
Combustion and other permanently open vents must not be blocked. Only use a closable grille where the system design permits control.
Place it clear of exhausts, pollution sources and areas prone to flooding or heavy splash. Follow product clearances and Building Regulations.