Glass in the dock: The glass debate

Are ‘all glass' commercial buildings set to become a thing of the past thanks to the new Building Regulations Part L? This was the extreme scenario posed at the Glass Debate, a one day seminar organised by Glass Age on 23 at One Great George Street, in London's Westminster.

The ‘sixth-form' style debate proved provocative, with Sean Affleck and Patrick Bellew stoking up the morning's proceedings. A big problem with glass is that buildings overheat, and the building services costs of all glass buildings add up to a very large carbon footprint, they contended.

That was the case against glass, but other speakers reminded that looking at one material in isolation is not very useful. A holistic approach is needed, and poor performance is often the result of lowering specifications to make up for budget over-runs.

For a new design to get approval, its carbon footprint now has been be passed by building control, and calculations will incorporate building services. Less glass might be a quick route to compliance, but several speakers pointed to better integration of shading, lighting and ventilation with building services will result in buildings that we like to look at and spend time in. The desire for and health benefits of natural light were also touched on.

The Glass Debate was sponsored by TuffX, Osprey Contracts, The Greenhouse Effect Ltd, and the Glass & Glazing Federation.

Welcome address by Rob Booth, Former Editor of Building Design The idea today is to look at one particular aspect of the new legislation Part L. That is the impact on architecture of the changing use of glass essentially. The fascination with glass among architects goes back quite a long way. To an extent architects have hoped that glass would make the building ‘invisible' and give dream-like qualities: It could change the way architecture is seen and how it works.

Recently the aesthetics of glass and the structural qualities of glass have been superseded somewhat by a concern about its thermal efficiency. The governement has cooked up this new regulation which will effectively guide the building industry's response to Kyoto, and other attempts to reduce carbon emissions.

We have a changing picture: From glass being a subject of aesthetics, it's now a subject of engineering and how we can increase the efficiency of building, which is quite an interesting shift, and presents some major challenges.

Ken Shuttleworth of Make mentioned in passing to me that glass was dead, and I commissioned him to write about the case for heavily engineered facades with glass where it needed to be, and not all over. It produced a real storm among our readership, which is modernist for the most part. They interpreted it as an attack on the guiding principles of contemporary architecture of the last 10 to 30 years.

What this is all about is a shift in attitudes and how we respond to that

Sean Affleck, make

The Case Against Glass

Sean Affleck, Make If you want to get a sustainable design, you don't want to be starting with buildings entirely made out of glass. We have a responsiblitiy as designers to deal with sustainability. What this is all about is a shift in attitudes and how we respond to that.

The energy consumption of some of these new schools is insane. We're building all glass buildings which would bake or lightly freeze our students if it wasn't for air conditioning.

Don't go with all glass, it's not essential to sell the building. Work with us to make it better. Our designs still do some very interesting things with glass and we try to get daylight deep into the building.

Patrick Bellew, Atelier Ten Buildings create 50 per cent of UK emissions; in London, 70%. We have a fundamental responsibilty that we cannot avoid. We must embrace this and work our way forward.

Over half of that is about increasing the performance of the wall. ‘All glass' buildings will be seen as second class, as ‘very Eighties'. We must look forward.

Often it's the client who doesn't really care. It's all about putting a building up well, quickly, and on time. Cost in use is not an issue. Even for the tenant, who runs the building, cost in use is relatively small and there are bigger things to worry about.

We should think about running costs from day one. How the building uses energy and how to reduce this. It's all about how we value energy as a resource and how our clients respond to that. We have to put to the client the cost of these gas guzzling buildings.

One cop-out when you sit with your energy model is to downsize the area of glass

Stephen Ledbetter

Before there was air conditioning, architects had the responsibilty to produce ‘good weather' in buildings. Since the invention of air conditioning, this has shifted to the engineer.

Regulations are pushing the technology, but the improvement in the glass has been less than the improvement in solid walls. Passive solar gain does a bit, but the bigger problem with too much glass is to do with overheating.

The Case for Glass

Stephen Ledbetter, Centre for Window Cladding & Technology, University of Bath I support the Green argument but I think glass has a role to play in that. There are all sorts of psychological and health issues to having natural light in buildings.

We do have this dichotomy of whether buildings should be closed or open. The building skin is a filter really: It has to keep things out, and it has to let things in. As such issues of heat and light are two among these many. We shouldn't lose sight of what we are trying to achieve with the overall performance of the building envelope.

The building envelope dominates the building services and there are arguments to say we don't trade that correctly. We tend to degrade the building envelope rather than looking earlier at the true costs for savings that can be achieved in building services.

It's fundamental when we design buildings that we get the lighting correct. We've set out to design buildings based on the glazing and the incoming daylight. Today we can think of glass as more than glass - for example, backing marble onto glass as a laminate can give a completely different characteristic to the incoming light.

Glass technology is improving all the time. There are cost issues, but most of this technology becomes more affordable. Switchable glasses giving solar control from 20 to 80 and better are available and this will unlock the potential to control buildings.

What we need is another debate about the certification of the energy consumption of buildings

Matthew Kitson

At Bath, we have been experimenting with a ‘plug and play' window, which has a circuit controlling top and bottom vents and a blind. The cost of adding the chip is 50 pence per window. It's this kind of technology that will allow us to combine our blinds with our lighting.

Increasingly we are using brise soleil which don't conflict with the view out and give a better overall appearance to the building. They also allow us have larger ventilation openings in the inner wall. These advantages are not fully realised.

Do we want to design buildings with lower glass ratios to simplify desings for cooling? One cop-out when you sit with your energy model is to downsize the area of glass and not worry too much about the internal environment or the physiological needs of the occupants in terms of daylight.

Or should we put in design effort to deliver buildings with more glass for all aspects of building performance? I would argue for the latter. We need regulations to deal with the dynamic building rather than the static building. Ultimately, glass produces some stunning buildings, and I think everyone can recognise those buildings which look really good when they are glazed.

Matthew Kitson, Hilson Moran Partnership There's something missing from this debate. It's actually about the whole energy and carbon consumption of the building. The bit that's missing is the implementation of the Energy Performance and Buildings Directive, namely articles 7 to 10. This to me is disappointing because it would give us engineers and design teams feedback about success or perhaps not of the performance of a building, and how we could do better next time.

Look at the success of this type of certification on white goods. There's a scale to A to G and in some categories of goods, they are now all A+ and that's what people want to buy.

It's important that it's the right skin for the right building but there are a number of different solutions that can be applied. External shading, ventilated facades. It's also about the whole energy consumption of buildings - that's the skin, the systems, and how we use buildings. What we need is another debate about the certification of the energy consumption of buildings. That to me is the bigger picture.

The Demands set by the New Regulations Paul Everall, LABC Local authorities are always happy to talk to architects before they put in an application. I'm not saying they will have an answer to all your queries, but it may be that by sitting down together you can discuss whether a particular design is likely to meet that. As a result of competition from the private sector, local authority building control fully recognises that it has to provide speedy and helpful responses to architects and buildiers.

Part L will highlight what is supposed to have gone in, because if it’s not there, it won’t meet the target

Ant Wilson

There are two schemes in particular that we run, the Partner Authority Scheme and Type Approval. The Partner Approval Scheme is where an architect is working with a particular local authority, he can continue to do so wherever the building is being constructed, so he can build up a good relationship. We have several thousand partners using this scheme.

Type Approval is more of use to the products and systems manufacturers. This is where a design can be approved and given a certificate so that it can be accepted by any building control body in the country.

You can get further information from www.labc-services.co.uk The role glass has to play in meeting Part L regulations Ant Wilson, Faber Maunsell

There are four parts to the Building Regulations Part L: L1a , L1b, L2a and L2b. What are the requirements? It's very simple. If you're an architect you've just got to do two things - limit heat losses and gains through thermal elements (walls, floors, ceilings) and other parts of the building fabric, known as control fittings. Glass tends to lose a lot of heat and it certainly lets in heat gains, so the logical conclusion would be don't use so much.

But it's not quite as simple as that. It's a holistic approach. Looking at the new regulations, the way to get compliance has changed considerably. You've got to prove the carbon footprint of a building, which also includes air leakage characteristics as well as heat loss and solar gain characteristics.

You now have to pressure test a building and get it certified that it is fit for purpose. This is now a regulation. You will not be able to finish a building without all fixed building services being commissioned, and the performance data of the fans, boilers, chillers, and other equipment will be fed back into the calculations for the performance of the ‘as-built asset.'

Value engineering can sometimes mean extra budget to spend on photovoltaics and solar thermal aspects, but more often it means cost-cutting - it's coming in over-budget, and things have to go out. Often the sustainability issues go out: this can include cheaper plant that won't make a value saving over its lilfe. Part L will highlight what is supposed to have gone in, because if it's not there, it won't meet the target.

Beyond Transparency: glass with presence Graham Dodd, Arup When I first heard that glass was dead, I was very worried. Glass is a large part of what I do and it has been for the last 17 or 18 years. But being an engineer, it only took me about three days to work out that glass is really shorthand for transparency. For the last 100 years or more we've been using glass to achieve transparency. I think now is an opportunity to use glass that is NOT pretending that it's not there.

The future is more active surfaces, energy conversion, and being able to vary the reflection and conversion of energy as we want to

Graham Dodd

Glass has spent most of its history trying to be more and more transparent. Now there are opportunities to do lots of other things with it. Modern glass has some presence - it's not pretending to be absent.

Me and many of the other speakers here today have banged our heads against this dilemma between trying to achieve clear glass, open buildings - glass as a metaphor for open government and transparency - and the imperative to control these flows of energy in and out of the façade.

Using selective coatings we can get to a point where they almost reject everything that isn't visible light. Of course all the light is still too much heat because it's energy. That message has finally hit home, and almost everyone recognises that if you let all the light in, you've just got too much energy.

We've seen this development from small windows to larger panes, the 1960s and 70s trend for tinted solar control glasses, to multi-layer façades, ventilated façades, concealed shading elements and so on.

We're now at a point where that development route has run it's course. We've got glass as selective in terms of energy transmission as it can be and there are lots other things that we can rediscover about glass. It's a great substrate for chemical and biological processes, engineered on the surface. It's a great substrate for converting energy, building semi-conductors on it. It's been talked about as recyclable for many years and we're only beginning to see real useful products out of recycled building glass.

On the surfaces, nanotechnology is beginning to manipulate atoms individually. We can start to do some very interesting things.

The hydrophobic route to self-cleaning glass has been around for some time. You can also go in the opposite direction and make it water-attractive. Applying a coating of titanium dioxide on the glass has this effect on the glass when under ultra-violet light. It's almost as if there's a permanent detergent there: the water gets attracted to the glass, lifts of the dirt, and you can see through this film of water. So there's a way of making the glass do something very useful, saving on access and improving the view through it.

Another remarkable thing you can do with engineering at nano-scale is you can start to build very thin layers which have got fantastic insulation properties. This technology is opening up to provide insulation in very much smaller packages. With glass being a low cost, flat, stable substrate, maybe we can do these things economically before long.

Lighting is a very important issue, and we should move it more central to the agenda

Grant Daniels

We've seen the development of photovoltaics from crystalline silicone cells encapsulated between panes of glass. In terms of converting energy, photovoltaic using nano-structured surfaces produces much more efficient photovoltaics with a wide band of light wavelengths they can absorb, and targets of 50 per cent or more light being converted into electricity.

Electrochromic products are just turning the light into heat by absorbing it at the moment. If we could get these product ultimately to switch between allowing us a clear view and lots of daylight to absorbing it and converting it into electricity, then we can see some much more smart things happening on the surface of the glass.

The future is more active surfaces, energy conversion, being able to vary the reflection, the conversion of energy as we want to; and using glass to deliver colour and translucency, texture and opacity. The forms are going to get more complex, and maybe the transparency's going to move into the interior of the building.

Skylight and Energy? The Elixir to well-being in the workplace is under threat. Grant Daniels, Zumtobel Staff Lighting Can lighting modify behaviour? Recent far reaching research has proven that different forms of lighting can have an impact on motivation, persistance, vigilance, accuracy, comfort, satisfaction and happiness. None of those individually relate to human performance in terms of efficiency in the workplace but they all very strongly correlate towards it.

As far as the workplace is concerned, light and glare affect what people do and can do, and lighting quality affects what people choose to do. This is contextual to recruitment and staff retension, which is increasingly a huge problem for the building's end users.

On the lighting cost and lighting control costs, to get Best Practice is very little more spend. To link an electric lighting system with a blinds control system is peanuts compared in the overall scheme of things, with much better comfort conditions for the end user.

Let the mechanical engineer specify the glass to meet the required performance; bring the lighting specialist in to advise on seamless daylight / electric lighting integration; use light re-directing blinds on the top third of the window, use controllable re-directing blinds for mid-third, and re-configure the luminaire layout to take advantage of increased daylight penetration. Lighting is a very important issue, and we should move it more central to the agenda.