Are tall buildings more energy-hungry?
Tall buildings are all the rage amongst designers and architects at the moment. The race to be tallest has heated up in recent years – but those buildings themselves might be heating up at a higher rate than first beleived, new research suggests.
A team from University College London (UCL) has found that buildings use more energy per square metre the taller they are.
Electricity use per square metre can be as much as two and a half times greater in high rise office buildings of 20 or more storeys than in buildings of six storeys or less. Gas usage also increases by around 40% the taller the structure.
Total carbon emissions from gas and electricity from high-rise buildings are twice as high as those from low-rise buildings.
So why does this phenomenon occur? The team at UCL’s theory is that taller buildings are more exposed to heat and cold, making them more sensitive to temperature changes, and requiring more heating or cooling.
Over 610 office buildings around the UK were examined, with researchers paying particularly close attention to energy consumption.
UCL’s Professor Phillip Steadman said: “The use of air conditioning plays a part in but does not provide a complete explanation of these results. On average, carbon emissions from air-conditioned offices are found to be 60% higher than those from offices with natural or mechanical ventilation.
“It is not the case, however, that the high-rise buildings in the sample are air-conditioned and the low-rise are not. The sample includes buildings of both types, of all heights. The increase in emissions with height is seen in buildings with and without air conditioning.”
Residential buildings in 12 London boroughs were also scrutinised by the UCL team. Here, they found gas use increased substantially with height. Electricity use also increased but not as dramatically.
Professor Steadman added: “We suspect that the reasons for our findings are connected with the physical and meteorological consequences of building higher. Air temperature decreases with height, and average wind speed increases.
“Taller buildings that stand up above their neighbours are more exposed to these strong winds, as well as to more hours of direct sun. Thus energy use for heating and cooling would both be increased. But these hypotheses have yet to be tested.”
A third part of the study looked at the relationship of different forms of building to their densities, where density is measured by taking the total floor area and dividing by the site area.
This project has shown that the densities achieved by tall towers can be achieved with lower-rise slab or courtyard buildings in many cases. It might always necessary to build tall to achieve high densities and energy use could be greatly lowered by building in different forms on fewer storeys.
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