Examination of Witnesses (Questions 420
- 428)
TUESDAY 5 FEBRUARY 2002
MR ANDREW
ALLSOP, MR
PETER BRESSINGTON
AND DR
JOHN ROBERTS
420. Was this done by two individuals?
(Mr Bressington) This was a way they decided
421. There is no system where somebody or some
authority is responsible. Would you say this is a gap?
(Mr Bressington) There is a gap, I think, yes.
Chairman
422. Are you saying we should have new regulations
for all tall buildings or just those over 30 metres?
(Dr Roberts) I have not come to any conclusion, I
am afraid. I know these things take some time. By the standards
that apply we are committed to quite a quick response and are
intending to publish a guidance document by the end of March,
which is really quite quick.
423. Yes, it is. If we are dealing with the
elements, if we can move on from fire to wind, the windy city,
Chicago, is that name given to it because of its historic position
or is it because it got so windy between the skyscrapers?
(Mr Allsop) By all accounts at one time they used
to have an area round the goods yard which was completely covered
in black smoke and it did not move round very much. In fact the
wind climate of Chicago is probably a bit less windy than London.
The problem in Chicago is that you have the lake and the wind
comes straight across the lake and straight up against the tall
buildings and they catch the wind like a big sail and deflect
it down towards ground level and produce the winds that you find
there.
424. The skyscrapers are to blame for it?
(Mr Allsop) The skyscrapers and the arrangement of
the skyscrapers there are partly to blame for that, yes.
425. Is it relatively easy if you are putting
up a new block to see what effect it is going to have on the micro
climate?
(Mr Allsop) When we put up very large blocks it is
treated very seriously indeed, they are usually wind tunnel tested
to measure the wind speed up of the various directions. We have
to take account of the shape of the building and the surroundings
are very important as well to the wind that is created in the
streets. We take account of the wind strength and how long it
blows in various directions and work out the percentages of time
that the wind exceeds certain criteria. On that basis you can
get an assessment of how windy one place is compared with another.
That is done pretty thoroughly for the taller buildings. The problem,
as I see it, is not these buildings—they are checked out—but
a lot of the wind problems you get are not necessarily associated
with particularly tall buildings. 20 storey buildings are very
wide and orientated the wrong way against the wind can create
quite a wide area of poor wind conditions which are unusable for
sitting out or anything like that, whereas a tall building with
a narrow floor plate creates a much smaller wind. Since about
the 1970s these techniques have been developed for evaluating
the wind and, therefore, we have the tools to manage this. You
are probably aware of places like Centre Point where they deliberately
created an open square in front of it as part of the merits of
having a 100 metre building. Those open spaces allow the wind
down and in. That is something that the planning officers need
to be aware of when they are asking for these areas of the quality
you are going to achieve in those areas. We can quantify it but
it is up to somebody else to decide what the merit is of a particular
target for those spaces.
426. You can design a tall building and you
can design a nice public space in front of it without it being
too windy?
(Mr Allsop) The important thing is to be aware of
the quality of space that you are creating and that it is appropriate.
If you are looking for a quiet, calm park then what you need is
nice Georgian, squared, low-rise buildings of equal height all
the way round it if that is what you want. You cannot just arbitrarily
pick a point and say, "I want this here, therefore I can
have it", because it does not quite work like that, you sometimes
have to work hard to achieve that.
427. You think a lot of extra tall buildings
could put be into the City of London without making it a windy,
unattractive street environment?
(Mr Allsop) It needs to be done carefully. The Chief
Planner of the City of London has taken quite an interest in this.
In other areas there is, perhaps, less interest taken in it. I
would say the problem is not one specifically of tall buildings,
even ground scrapers are going to create a bad environment if
handled wrongly.
428. Lastly, this new generation of tower, is
it going to have cutting edge technology, do we need to worry
about that or ought it all to stand up? Sometimes when I am in
a tall building and I see what appears to be a thin think piece
of glass between me and the street below that gives me a feeling
as to what would happen if the piece of glass fell out. Should
I be worried?
(Dr Roberts) I do not think you should be worried
in the structural sense. I worry, as you do, about the view, looking
out through the glass, but that is a different matter altogether.
I think that the evidence is that the designs for large and small
buildings are good in the basic structural sense. I think the
attention is to do with the management and use of the buildings
which have large numbers of people in them rather than those sort
of issues like is the glass too thin.
Chairman: On that note can I thank you very
much for your very helpful evidence. Thank you very much indeed.
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