Ventilation Of a Habital Room Without A Window

20 Aug 2010
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United Kingdom

I have a question regarding Approved Document F - Ventilation - 2010 Edition.

Paragraph 5.15 states:

5.15 A habital room not containing openable windows may be ventilated through another habitable room if:

A. There is, from the habital rooms to outside, provision for both:
i. Purge ventilation with total area given in Diagram 3 based on at least the combined floor area of both habital rooms; and
ii. Background ventilation of at least 8000mm-squared equivalent area; and

B. There is a permanent opening between the 2 rooms as given in Diagram 3 based upon the combined floor areas.

We are satisfied with the part A, the purge ventilation satisfies the 1/20th of combined floor area of the rooms and we easily have the 8000mm -squared trickle vents over the new windows.

My question is regarding the B. statement. When looking at Diagram 3, there is not any guidance given regarding the size of the opening between the two rooms which is supposed to be based upon the combined floor areas. Is there a minimum sized aperture necessary to qualify for this method of ventilation, or will any size aperture work?

Thank you in advance!
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