The overall appearance of many non domestic buildings is
determined by the transparency and form of the building
envelope. This lecture seeks to highlight some of the conflicts
that emerge when trying to realise the design intent and manage
client expectations while simultaneously meeting the many
technical challenges of doing so.
I'm a bit of a glass anorak, so this is not essential, but if
you end up at a company who does specialise in glass, this is
the sort of thing, unfortunately, that they, on the client
side, that they are quite interested in.
So they will expect you to be able to do all the technical
stuff, G values, the U values, transmission rates and all the
rest of it. But they will also expect you to have some idea
about what the effect of your decisions is on what the glass
looks like. Some of the key things, I suppose, will be to
understand what the design intent is.
In other words, what the client really want?
What were they really expecting?
And expectations are generally managed by either renders and
images or physical models.
And you will have to spend a lot of your time again, if you go
into the glass side of the industry, managing their expectations
because what they want and what they can actually get for the
budget they've got isn't always accessible.
Also, you've got to be aware of the implications of making
subtle changes. So although in past lectures we talked about the
effects of G values and the impact of things like low e
coatings, what we haven't talked about is how that affects the
look of the glass.
Generally, overall, the completed facade tends to be slightly
more transparent than the initial concept, depending on whether
you've got low e or reflective coatings on it.
So all sort of things that affect that, and there's a lot of
them, quality and level of light.
So obviously it changes from day to night a lot.
The area makes a difference.
So if you're looking at acres of glass, it makes a difference
between that and looking at a smaller area of glass.
The viewing angle we've talked about already, how, as you offset
the viewing angle, the reflectance changes and gets more and
more and more. And of course, the distance will be affected by
the reflectivity of the glass.
I'll talk about different types of transparency and form.
So as we go from more transparent to less transparent then the
form becomes much more important.
Transparent buildings, or highly transparent buildings, tend not
have as distinct a form where as less transparent buildings
have a much more solid appearing form.
Again, and we'll look at views in and out because no one really
thinks about what it's like on the inside.
I'll talk briefly about Fritted Glass.
I've mentioned it before, but I'll look at some examples of
Fritted Glass instead of more tints and shadings and so on.
I'll finish off with a slightly obscure thing.
We don't really think about this much, but there is a bit of a
problem with polarised light and reflection from buildings and
bird kills.
Stay with me on that one.
Course, for Specialist Glass, as last, a couple of weeks ago, we
talked about how do you change, or how do you improve, glass on
particularly listed buildings which have vintage glass or
specialist glazing units.
How do we replace those, and I'll finish off with media facades
and if we've got time, I'll just talk a bit about some glass
research. So in terms of the levels of daylight from the inside,
from the user, it does give shape to the building.
So with sufficient light, it can help you, guide you and take
you around a building. But also the objects within the building,
especially if we're in a museum.
It does give them shape and form.
And whatever type of light you do use, or daylight you do use
will determine what level of contrast, and form, you get.
When it comes to quality of internal light we'd be talking about
levels, in other words, making sure we meet minimal levels and
we've got a maximum level which minimises glare.
But you don't necessarily need to have vast quantities of
daylight to have a good quality of light because it does depend
on the building. So if we look at say this sort of building
where it's supposed to be a much quieter, more sombre
environment, so actually you can achieve a good quality of light
with very, very small openings.
And the first thing you notice is the intensity or the reveals.
I mean they're huge. So what they're trying to do is make the
most of the tiny little windows they have.
So it gives them privacy.
It gives them a very sombre quiet atmosphere with small windows.
So it's thick walls.
You've got good acoustic attenuation as well as its quiet.
So you don't necessarily need masses and masses of glass to
achieve good lighting levels, it does depend quite severely on
the type of building you're illuminating.
The glazed area again, if you want to achieve the appearance of a
large glass box or in this case, a large glass blob, you don't
actually need the whole facade to be fully glazed.
So this is the city hall in London.
The building here has between 60 and 70 percent glazing.
The glazed area is that these strips of glass here and then they
have individuals insulated spandrel panels with a glazed front,
so they glaze spandrel panels.
So from a distance, it looks like a glass blob, but actually
it's not all fully glazed.
And if we compare that with the building next to it, which is
almost 98 percent glazed, the city hall will probably have much
better control of its daylighting and it's overheating and glare
because it's only got 50, 60, 70 percent glazing to deal with.
Over here, with 98 percent glazing, they've got people with
blinds up and down, the lights are on or off all the time, it
limits internal flexibility.
You may not necessarily be able to put your desk right up
against the window because of glare and daylighting issues.
So it's not necessarily urgent to have a 100 percent glazed area
to give you that appearance of a glass box.
Viewing angles quite important, as we've said, as you become more
off angle, then the glass appears less and less clear.
So if we're looking from the outside in, for instance, at the
Louvre, I mean, they have low iron glass.
But because of the age of the building, if you look at the
amount of structural material they have, if they built the same
building now, or the same pyramid now, you could probably get
away with 50, 60 percent less frame and bigger pieces of glass.
But when you're looking from the inside out, you can see how
clear it is. It is very, very low iron glass.
The idea of having a pyramid at the Louvre was controversial at
the time anyway.
One of the biggest concerns was vandalism, they felt that with a
glass box in the middle of Paris, people would just vandalise
the glass. So just in case, they actually kept the equivalent of
two pyramids worth of glass, that's a lot of extra glass.
So they got enough glass to make two more pyramids just in case
any of the panes got damaged.
To me, that's overkill.
Normally you'd only require maybe one, two, five percent tops in
terms of spares, but in 30 years, they've not needed any of
them. So there's a little, there's a storage depot somewhere in
Paris which has enough glass to build the pyramid twice.
Moving on to viewing angle.
It's not absolutely clear exactly why the viewing angles
important in this building.
But when you move down the side of the facade, I mean, you can
see that this is just a normal plain glass facade, down the
side there's something odd going on here.
What they've done is they've added glass fins to the side of the
building. And the original intention was to actually articulate
the shape and side of the building with the glass fins.
I'm not sure you can make it out, but you notice there's a
slight wave and a curve, that's actually articulated by the
shape of the fins. So each fin itself is just slightly different
in shape and profile from the next one and it gives the
impression of a waving facade.
Unfortunately, the original client was an IT company and they
decided to move out and then they ran out of money, and the idea
was to actually illuminate the ends of those fins so that at
night you ended up with sort of wavy glass facade.
It did seem excessive expense just for the sake of getting a
wavy facade. I think you could have done it better, differently.
Here's some better examples where instead of actually having
lights at the end of the facade, all they done is illuminated
the plain behind the facade.
Again, not quite sure why they particularly want a wavy facade,
if you had in the brief I want a wavy facade, there probably
other ways of doing it, but maybe this is slightly cheaper than
having a faceted glass facade.
We've had a look at this building before the Willis building in
terms of viewing angle.
This building appears to be almost 100 percent glass from one
angle. If you move 90 degrees, you'll find actually that that
particular facade, facing 90 degrees from the glazed angle, is
completely solid. So it has a clear side on a kind of solid side
that's not necessary to do with articulating for the building.
It's more to do with maximising daylight from this orientation,
but minimising glare from this orientation.
On about distance, I'll be talking about mirrored glass later on
as well and some other impacts of mirror glass.
But if you have a highly mirrored or highly reflective facade,
then the distance is incredibly important.
The eye is incredibly good at picking out small faults in glass,
or rather not so much the glass, the joints between the glass.
So you have to make sure that A.
the glass is incredibly flat.
If you have a curve, as you have on this top left hand picture,
having completely flat glass over that gentle curve will give
you the reflection that you're after.
Even if one or two of the panes is slightly off and not quite
flat, your eye tends to pick it up and the further away you go,
the more exaggerated the effect becomes.
So, for instance, the top bottom left hand one, the first thing
you might notice is the fact that all the joints between the
glass aren't quite consistent.
And the way it's lined up isn't quite consistent.
And that breaks up the reflective image.
Moving to the right, I mean, obviously, this middle one clearly
was never designed to be spectrally flat.
It was deliberately designed to be unflat and wavy, they wanted
that effect of rippling water and so on.
And the one on the bottom right.
Again, they deliberately wanted to give the effect of not flat
glass. And they tried to mimic, I think, a sort of mirrored log
stalk. So you can play about with the facade and the reflectance
of it. But if your intention is to have a perfect reflection
like the top right, every single pane has to be incredibly flat
and the junction between them has to be pretty well perfect.
What about the level, the amount of transparency?
Back in the old days when we used to make models of buildings
we'd make them out of perspex, and perspex was never that good
at being clear. Here they've used white perspex because they
wanted something which had a slight frosting on it, but in the
end they couldn't afford the glass and then ended up being sort
of normal clear glass.
So the design intent, and if you showed the client that, and
they ended up with that, they probably wouldn't be that
disappointed, whereas if the model looked like this, and the end
result looked like that they might be.
You don't know what their intention is, very often you find a bit
of post rationalisation of the final design.
If the client loves it, then he'll say, yes, that's what I
intended to happen. If they don't like the look of it, then you
have to start managing their expectations.
But at that point is normally too late because they've already
paid for the building. In general, buildings aren't supposed to
be completely transparent.
It's very hard to get a complete transparent building.
Take an early example.
This is the first version of Apple's Fifth Avenue store.
Because of the technology at the time, they were restricted to
relatively small bits of glass.
You notice that each piece is just under three metres.
OK, so remember what we said about the size of glass.
They wanted longer pieces in order to connect them all together.
You've got lots of little metal connections and it isn't quite
what they were after.
Whilst it is a glass box, it isn't that transparent, and you
notice the colour as well, there's a slight greenness to it.
So it's definitely not low iron glass.
And again from various different angles you can see, actually,
rather than seeing a transparent box, all you're seeing is the
colour of the glass and all the little tiny connection details.
And what happens if you tint the same glass box?
Here we've added a very slight tint to it and all of a sudden the
whole box becomes more of a cube.
You can actually see the shape and form.
Here you can see the form, but the form is slightly disturbed by
the fact you've got all these little connections in the detail.
But as soon as you add a tint, then the form becomes much more
precise. So here the designer wanted to achieve a light glass
box that looks like a box.
Then you've probably achieved the desired effect.
And also because it's in Madrid, having the light tint is
appropriate for the area because it doesn't look as though
you've got any openings. So it doesn't look like it's going to
be ventilated very well.
So he's going to need quite a heavy tint to make sure the
building doesn't overheat too much.
Others have actually used the differences in transparency.
So they've got an opaque facade at the back for the piano on a
highly transparent but very reflective glass for the violin.
So the focal point is actually the bit that you don't normally
see.
Normally you don't look at glass boxes in the same way, but
they've actually used it to shape and articulate the entrance to
this music centre. I hope you have enjoyed this lecture and it
has opened your eyes to resolving some of the complexities of
successfully delivering highly building envelopes.
And we look forward to seeing you on the course in the future.