Reducing construction emissions could save up to 6 GT carbon by 2050

Following certain recommendations such as using steel frames and opting for tile cladding in multi-storey building design to decrease embodied carbon emissions and operational energy could save up to six gigatonnes of carbon by 2050, according to a new study.

Researchers from the University of Cambridge and Bath, UK, devised a computer model and used it to estimate that these recommendations could also save between 28 and 44 per cent of annual heating and cooling costs, using technology that is currently available.

Their findings are reported in the journal Applied Energy.

Construction and operation of buildings account for more than one-third of global emissions and energy use. While buildings are a large part of the current problem, they are also a significant lever for change, said the researchers.

For their study, the researchers looked at shape, size, layout, structural system, windows, insulation, ventilation, and use parameters, for both residential and office buildings, across different climates.

The choice of structural frame type, the researchers found, has a large effect on embodied carbon and cost of both residential and office buildings.

They also found that cheaper frames tend to be high on embodied carbon and vice-versa, pointing to a trade-off.

Cross-laminated timber floor slabs with laminated beams or steel frames are the lowest carbon solutions, they say.

They also say that as the number of storeys increases, so do the embodied carbon values.

In cladding, brick cladding leads to significantly higher embodied carbon and cost compared to lighter sheet or tile cladding options, they said. Brick clad buildings were found to be up to 20 per cent more carbon intensive and 15 per cent more expensive than sheet or tile clad buildings.

More the cladding, more the quantities needed in the frame to support the cladding loads, they said.

In terms of operational energy of a building, the researchers found, by examining the influence of climate on the sensitivity of building design variables, that it is much more challenging to reduce energy use in hot and humid climates than in cold and moderate climates.

For example, for the tropical climates of Singapore or Lagos, however, high humidity and high temperatures mean there is a reliance on cooling. The more occupants within the building, the more cooling energy is needed to dehumidify incoming air, the study said.

For temperate climates, such as that of London, a building's shape and its window configurations are the most impactful design decisions for heating and cooling, the study said.

In the hot and arid climate of Cairo, decisions about window-to-wall ratios are critical, the study said. This is because the more windows there are, the more the building heats up through solar radiation.

The researchers also found that smaller windows and a lower solar heat gain coefficient - the fraction of solar radiation admitted through a window - has more influence on the efficiency of office buildings than it does on residential buildings.

This is due to the former having a larger number of occupants and heat-emitting appliances.

The use of mechanical ventilation with heat recovery is one of the most important levers to decrease heating and cooling energy, say the researchers, especially for office buildings in hot, humid, and cold climates.