Effect of glass facades on the environment

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Effect of glass facades
Glass facades
Dr.(H.C) S.B.Raghunath
Dr(HC)S.B.Raghunath, Founder – Director, Protect Infrastructure Systems Pvt Ltd

Modern skyscrapers and their glass facades characterise the image we have of our big cities. In recent years, glass façades have started to receive more and more criticism, as they have many negative influences on the environment.

Approximately 250,000 birds die every day in Europe In North America, around one billion birds die every year due to collisions with glass panes flying into glass façades, and can fly on later due to internal injuries, fractures or bleeding.

Architects like to use highly reflective glass because it is particularly energy-efficient: most of the sunlight is therefore not able to penetrate the building, which reduces the heat development inside. The natural surroundings are reflected in the glass façades; birds don’t see them as an obstacle. The reflection from glass façades is also disruptive for motorists.

Source: news.nationalpost.com

In past years concavely formed façades in particular have received a lot of criticism, as its glass, metal or steel reflect the sunlight onto one place like a magnifying glass.

As a result, temperatures of over 100°C can be reached. Concave facades exist because real estate companies enlarge the space of the more expensive, upper levels, in order to achieve higher rental incomes.

The upper levels then project far over the floor plan of the building. The arched façade is hot enough to singe the hair of hotel guests in the area of the pool deck and melt plastic chairs.

Arched façade can bundle sunrays together from the façade deformed cars on a neighbouring street and can melt plastic. To show the intensity of this, journalists used the concentrated heat to fry eggs. Several parking spots had to be closed off on the street. Since then, aluminium slats were attached to over thirty floors on the south side of the façade, which stop the solar reflection. The refitting cost approximately £10 million. Despite the massive glare effect, the building on Fenchurch Street had received an excellent evaluation by the British BREEAM.

Sustainability certificates are awarded because of the energy efficiency of a building “without considering the adjoining microclimate”, criticises architect Julie Futcher and town planner Gerard Mills from the University College Dublin. Due to the increasing number of skyscrapers with reflecting glass façades, these characteristics of buildings, which influence the microclimate of their surroundings and intensify the “Heat-island” effect in cities, should also play a role in the sustainability assessment of a building.

The Walt Disney Concert Hall in Los Angeles has shown just what kind of effects buildings can have on the microclimate. The building designed by Frank Gehry has a façade with concave shaped surfaces made out of polished stainless steel. The façade raised the ground temperature on the pavement so much that plastic began to melt. The temperature in the neighbouring houses rose to above 9°C, with the neighbours having to set up their air conditioning. The energetic balance of the neighbouring buildings deteriorated significantly. Similarly the 42-storey Nasher Sculpture Museum in Dallas, Texas, was also affected. The façade of a neighbouring building was fitted with photovoltaic modules, which directed sun rays directly into the museum and damaged sculptures.

Attack on pedestrians

Façades are not only able to reflect the concentrated light downwards, they can also direct the wind downwards in a bundle, which leads to a so-called wind tunnel effect. The wind meets the façade and “then just goes straight down to the ground because it can’t go around the building,” explains Lindsay Smales from Leeds Beckett University in the UK.

In Leeds the 32 floor high Bridgewater Place has led to strong wind gusts, which at wind speeds of 130 km/h didn’t just throw passers-by to the ground. In March 2011 a lorry swirled through the air as it drove out of the slipstream of Bridgewater Place. One pedestrian died as a result.

Curbing the effects of glare

The façade of the ‘Walkie Talkie’ (20 Fenchurch Street, London) received worldwide attention through the concentration of solar radiation

What are the possibilities of curbing these effects?

“When the skyscraper was first built, there’s not much that could be done to mitigate the problems with the microclimate and the effects of the wind”, reveals Lindsay Smales. “Ideally the glare effect of a façade should be determined during the building planning, with help from fluid mechanics (Computational Fluid Dynamics, CFD),” explains Vicente Montes-Amoros from the American engineering firm Curtain Wall Design & Consulting.

CFD tools can determine solar reflections with the movement of the sun. 3D models and precisely calculated predictions are an enormous help for the design of sophisticated façades. In addition, building shapes and building orientations, road conditions and material can all be included in the analysis and create the condition for a complete picture.

“In Sydney, Australia, a prior analysis of the glare effect must be implemented. The reflection of building materials is restricted to 20% in Sydney and Singapore,” explains Montes-Amoros.

Experts call for ban on glass skyscrapers to save energy in climate crisis

Air conditioning is used to avoid greenhouse effect but cooling buildings adds to carbon emissions

People sit on deckchairs near the Lloyds of London building during the heatwave. Photograph: Dominic Lipinski/PA

Leading architects and engineers are calling for all-glass skyscrapers to be banned because they are too difficult and expensive to cool.

“If you’re building a greenhouse in a climate emergency, it’s a pretty odd thing to do to say the least,” said Simon Sturgis, an adviser to the government and the Greater London Authority, as well as chairman of the Royal Institute of British Architects sustainability group. “If you’re using standard glass facades you need a lot of energy to cool them down, and using a lot of energy equates to a lot of carbon emissions.”

Glass-fronted offices, from high-profile buildings like the Shard to shopping centres and industrial parks, have become popular with architects and their clients because they create an arresting view in a city skyline, let in lots of natural light and provide great views for those inside. But the sunlight also brings heat, and in sealed buildings there is nowhere for it to escape to naturally – something which, as Britain sweltered in a record-breaking heatwave last week, will have become apparent to many working inside them.

To avoid this greenhouse effect, air conditioning has been the standard solution. But that is problematic in itself. The International Energy Agency estimates that about 40% of global carbon dioxide emissions come from constructing, heating, cooling and demolishing buildings. Air conditioning is a growing proportion of this: energy used on cooling has doubled since 2000 and accounts for about 14% of all energy use now.

In April the mayor of New York, Bill de Blasio, said he would ban all-glass buildings and force developers to retrofit existing buildings to make them more energy-efficient, although the “ban” was later clarified to mean excessive use of glass and steel.

Sadiq Khan, the mayor of London, has ruled out such a plan for the British capital, but Sturgis believes the American is on the right lines. “Certainly, I think there should be a ban,” he added. “The connection needs to be made between the climate emergency and all-glass buildings. But the connection hasn’t been made yet.”

Martin Fahey, head of sustainability at Mitsubishi Electric, warned that higher temperatures meant that air conditioning machines now needed to work harder than in the past. “Most air conditioning equipment is designed to give an internal temperature between seven to 10 degrees lower than the ambient temperature,” he said. “I suppose it’s fair to say if that machine is getting old or has developed a fault somehow, Murphy’s law being what it is, something will go wrong and it will fail.”

The new version of the London Plan, the rules for all development in Greater London, which is due to take effect next spring, will require construction firms to make an assessment of a building’s energy use across its whole life-cycle. Sturgis hopes that investors will react more quickly.

“Big commercial tenants don’t like standing up in front of their shareholders and saying they’re doing embarrassing things,” he said. “No one wants to be treated as ‘Mr Climate-Dirty building’ and I think this is going to start happening.

“I’m advising a bank that wants to build a very big building in London – which I can’t tell you about, but I’m having this exact conversation – I think the building could be obsolete by the time it’s finished.”

Glass has some advantages: in colder weather, the warming effect of sunshine – “solar heat gain” in the jargon – means less energy on heating. Architects can still use this with smaller windows, according to Simon Wyatt, a partner at Cundall, an engineering firm, and a UK Green Building Council committee member. He said natural ventilation would save “up to 60 to 70% on our air conditioning loads” but in city centres, air pollution and traffic noise make this impossible.

Newer buildings use special types of glass that can become more opaque to block sunshine in hot weather, or even generate electricity themselves, such as the Edge building in Amsterdam. It uses about 70% less energy than most buildings but is not glass-fronted on all sides – the southern, eastern and western sides have smaller window openings to reduce heat gain, and openable windows.

But these laminated glass panels still contribute to the climate crisis, according to Sturgis, because they are much more expensive to make and almost impossible to recycle.

“To mitigate the amount of energy used to cool these buildings, you have to produce a really complicated façade, which is usually triple glazed,” he said. “But double glazed units and laminated glass don’t last very long – 40 years or so. So you have to replace your facade every 40 years, that’s also not a very good idea.”

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Impact of retro-reflective glass façades on the surface temperature of street pavements in business areas of Singapore and Tokyo

There are studies that evaluate variations in the surface temperature of street pavements caused by retro-reflective glass when applied on highly-glazed façades of high-rise buildings located in Singapore and Tokyo. To accomplish this, simulations are conducted on one experimental site situated in business areas of Singapore and another in the city centre of Tokyo. Incoming solar radiations on street pavements and heat transfers affecting their surface temperature are among the physical phenomena being simulated. As a result of the data analysis, it appears that the use of accordion retro-reflective glass on highly-glazed façades could noticeably reduce the surface temperature of street pavements in business areas of both Singapore and Tokyo, compared with other types of glass. A more significant decrease in the surface temperature can be expected in the experimental site of Tokyo, particularly near the summer solstice. On the other hand, the design optimization of accordion retro-reflective glass seems to be more effortlessly achieved in Singapore. These outcomes represent an encouraging step towards the reduction of building energy use, as well as the mitigation of the Urban Heat Island effect, from the use of retro-reflective glass façades in business areas of different cities experiencing various climates.

Among them, the specialized urban design can promote the urban heat island reduction efficiently, but it is too complex to yet a practical approach]. Increasing the green infrastructure can reduce the amount of infrared radiation and lower the urban surface temperature effectively [26][27][28][29], but this technology often needs to provide some land and irrigation water for plants [30]. In addition, several studies have shown that planted roofs have little effect on outdoor air temperature.  Solar radiation acts directly on urban surfaces and thereby, the urban surface temperature is an important factor on the application efficiency of retro-reflective materials. For covering retro-reflective materials on the window glass, Martin et al. found compared with the low-E glass, the surface temperature due to using retro-reflective glass with a reflectivity of 42% was reduced by 0.75°C and 7.75°C at least for the pavement surface temperature and glass surface temperature at around 12 pm, respectively. Inoue et al. compared the temperatures of the glass surface and the pavement surface for the single glass, the single glass with retro-reflective film and solar-shading Low-E double glazing.

There have been developments of coating COOLTHERM which will not reflect heat and also allow the ingress of heat. Thereby there will be minimal or zero load on the air conditioner while both cooling or heating. Since it is not a heat reflector there will be no effect on microclimate and can contain heat within itself. The coating life is expected to be 7 years and has to be recoated as efficiency denudes. Being a transparent coating it can be applied over automobile glass also to get reduced temperature ingress apart from being a hydrophobic material water won’t stain glass and improves vision during night driving also. Two coats are to be applied by spraying and wiped with a cloth after each coat dries. It is a do it yourself kit.

Source- https://www.nytimes.com, london.gov.uk/, breeam.com, researchgate.net

The views and opinions expressed in this article are those of the authors based on his own analysis.