Part F: Ventilation...

[Craig]

Time to blow a little hot air...

We are rebuilding two bathrooms in an extension to our 18C terrace.

Everyone but everyone seems to tell us we need extract fans, but I have read Part F and it seems to say that my mechanically operable purge ventilators (hmm, windows???) are acceptable for both the extraction and purge ventilation and that the background ventilation is assessed at the overall house level (and boy, does it leak!).

Is that correct? Are properly sized, opening sash windows enough or do I have to despoil my house with horrid nosy fans?

Many thanks in advance!
Craig

PS - perhaps I should also consider the benefit of my "innovative and creative" brick built passive stack ventilators too (chimneys anybody?)?

 

[Gervase]

You don't need the fans. However, if you have to endure a visit from a junior building inspector s/he may tell you you must have them. Gently point out that Part F is merely an approved document, and the only part that is legally binding is the paragraph in green at the beginning, which makes no metion of fans. It merely states that adequate ventilation must be provided. Then send the inspector on his/her way.
And, anyway, Part F was drawn up with horrible sealed modern boxes in mind, so its recommendations are hardly relevant to a period property (I mean, 'trickle vents'? *sigh*)