Part F says if there's external walls, rapid ventilation should be acheived by a window that opens more than 30 degrees, and is 1/20 of the room floor area. Venting is also allowed through a conservatory. The BCO wants to know how rapid venting will be acheived in my case. The rear extension (not a conservatory) will be built around the previous french windows, so there will be no direct window to outside. What is the usual solution to rapid venting in this circumstance, which must be common ? Thanks, Simon.
Going on the 2005 draft, where "rapid" ventilation is now called "purge" ventilation, Part F 1.12 and 1.13 applies. Basically, provided the French windows aren't screwed shut or removed, you just need to add the purge ventilation requirements of the inside room to the first room you encounter in the extension. i.e. that room will need large openable windows.
Text follows.
Christian.
1.12 In a habitable room not containing openable windows (i.e. an internal room) the requirement will be met if the room is either ventilated through another habitable room (see Paragraph 1.13) or through a conservatory (see Paragraph 1.14).
1.13 A habitable room not containing openable windows may be ventilated through another habitable room (see Diagram 2) if:
a. there is from the habitable rooms to outside, provision for both:
i. purge ventilation, one or more ventilation openings, with a total area given in Diagram 2 based on at least the combined floor area of the habitable rooms; and
ii. background ventilator, a ventilation opening (or openings) of at least 8,000 mm2 equivalent area; and
b. there is an area of permanent opening between the two rooms given in Diagram 2 based on at least the combined floor area of the habitable rooms.
I read this. Section b. sounds to me like there needs to be a permanent opening between the rooms, i.e "not screwed shut" is not OK, it needs to not have the doors. (That would not please the fire regs I suspect). It's section a. **AND** section b. This does not make sense to me.
Also, to add compexity, there is actually a small window to outside in the old room, but it is not sufficient to fullfull the purge, have an area about 1/25 of the room, not 1/20. Any further thoughts ? I may have to ask the BCO, but at this stage he is rather hard to get hold of. Email took 4 days to respond !
My understanding is that an opening can include a door or window. It is for purge ventilation, where the intended use is intermittent and is intended to include the throwing open wide of windows or doors.
The window in the existing window will easily meet the background ventilation requirement.
Remember that the Approved Documents are a guide, not a final statement of the law. The combination appears to considerably exceed the spirit and, IMHO, the letter of the document, in that you can easily provide sufficient reliable background and purge ventilation.
It would be very hard to justify not accepting your proposed solution.
It's just that I've got the maybe incorrect impression that my BCO is a bit over-picky. He wants me to state things that are obvious from the plans. I'll just add this stuff to the spec. Thanks, Simon.
I would write something on the plans about background ventilation from the window (add a vent to it if required) in the room, whilst 75% of purge ventilation supplied from this window, and 25% from the adjacent room. For that room, massively overspecify the purge ventilation, so there is no question of provision being marginal.
Just out of interest, what's the reasoning behind rapid or purge ventilation in Part F? Do building regs now seek to protect the acquaintances of those who just ate one too many VegeBurgers? Or the SWMBO after a lads' night on the curry take aways?
I think a lot of people think the regs are over-reaching themselves. Although some are annoying (like excess insulation in an otherwise solid-walled house), but understandable. Simon.
It's odd though that they seem to be doing it a lot faster this millenium than ever before. I blame the EU - it's their civil servants that need putting down more than ours. And our politicians for actually listening to the crap the bored pencil-monkeys spout.
Agreed. I wish (though it is obviously not practical) there could be strict regs for el-cheapo bulk builders, especially Barratt and Crest, and less Rule 1) No bodging Rule 2) NO BODGING! Rule 3) And no bodging! etc.
(with apologies to Monty Python)
Especially, "eg: thou shalt not construct walls out of plasterboard and the crappiest studwork you nicked out of the skip on the way to the site".
It's a clash of cultures. Th continental way, make rules which you know will never be taken seriously. Traditional British way, avoid making law which would involve public expenditure to maintain, but if you must make sure it can be enforced.
On 15 Feb 2006 01:45:20 -0800, a particular chimpanzee named sm snipped-for-privacy@hotmail.com randomly hit the keyboard and produced:
Either i) there should be a permanent opening (an opening with no doors) between the two rooms at least equivalent to 1/20th of the combined floor area, or ii) that the room covered by the extension has other ventilation openings (windows or external doors) which give 1/20th of the floor area.
The Public Order Act 1936 was specifically designed to deal with Oswald Moseley's fascists. However, it lay unused for forty years before some enterprising Yorkshire police sergeant used it against a couple of brawling drunks, opening up a whole new Public Order industry.
These days we seek to regulate everything. Once upon a time we laughed at Germany with 100,000 regulations; now we have more than they do, and they arrive at the rate of 3000 pr annum.
I suspect the driving force is the need to be seen to 'do something'.
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