Frequently Asked Questions...

Q. Can I fit a night vent keep or use a night vent position on the window to provide background ventilation, instead of a trickle ventilator, because I know the size of the opening provided by the old window?

A. "Means of ventilation" F1 – There shall be adequate means of ventilation provided for the people in the building. Paragraph 3.3 states "To comply with the requirement windows should include trickle ventilators". The alternative is the provision of another back ground ventilator opening of a known equivalent area in the same room (wall vent). If the equivalent area is not known the following sizes should be adopted:

For dwellings: Habitable room 5000 mm² equivalent area.
                   Wet room 2500 mm² equivalent area.

Control of ventilation paragraph 0.17 says "Manually controlled trickle ventilator (the most common type of background ventilators) can be located over the window frames, in windows just above the glass or directly through the wall (see diagram 5 in the glossary)". Night vent keeps and sliding sashes have been removed from the guidance hence they are not an approved method. BS EN 13141 does not set out a method for testing the equivalent area on these forms of ventilation.

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