According to the Council on Tall Buildings and Urban Habitat, there are nearly 140 supertall skyscrapers, buildings that are 984 ft. or taller, currently under construction. With the proliferation of supertall structures going up over the next five years, the question needs to be asked, ‘How green and sustainable can these skyscrapers be?’
The Shanghai Tower which completed construction this year is set to be the tallest LEED Gold Certified building and was designed and constructed to receive a 3 Star rating from China’s Green Building Evaluation Standard. The building used locally sourced and recycled materials in its construction.
The 120° curvature of the building made for a striking design, while having the added benefit of reducing wind loads which meant lighter materials were used for the structural elements of the building. This resulted in a 32% reduction in building materials used compared to a conventional building. This saved about $58 million and allowed for a reduced building footprint to add more green space to the site.
The Shanghai Tower also feature a double-skin façade that provides additional insulation to the building, similar to the way a double-walled thermos keeps hot beverages hot and cold beverages cold. The façades, along with other energy saving measures such as vertical axis wind turbines and geothermal energy, allows for a 21-22% reduction in energy use. Between the two façades are sky gardens located in each of the nine vertical zones of the building.
The tower is expected to save about 178 million gallons of water a year through rainwater harvesting and a blackwater treatment facility. These sustainable energy measures are expected to result in a reduction of the building’s carbon footprint to the tune of 34,000 metric tons per year. Pretty impressive for a 2,073 ft. tall structure consisting of 4.5 million sq. ft.
Green and sustainable is great, but the true holy grail for an eco-friendly skyscraper would be one that is net zero energy, one that produces as much energy as it consumes. The Pertamina Energy Tower under construction in Jakarta, Indonesia is planning to do just that. A majority of the energy will come from a central energy plant run on geothermal power. Solar panels will cover other buildings on the campus as well as being placed atop a covered walkway dubbed the ‘Energy Ribbon’ which will weave across the campus and connect the various buildings. The top of the tower will be open and have a funnel shape which will suck wind in and direct it over a series of vertical wind turbines that could provide up to 25% of the building’s energy needs.
The façade of the Pertamina Energy Tower was calibrated to mitigate solar heat gain. Semi-mobile sun shading curtains will allow sun to enter the building, but protect from the heat. The building will feature a blackwater treatment plant and there will be zero water discharge. Rainwater collection and water recycling will also be used to further reduce water usage.
The Pertamina Energy Tower will be 1,716 ft. tall and have a gross floor area of nearly 2.6 million sq. ft. The current largest net zero energy building certified by the International Living Future Institute is the Packard Foundation Headquarters at around 51,000 sq. ft.
When we talk sustainable, we sometimes fail to consider the building materials themselves. Skyscrapers are primarily made from concrete and steel, two very big producers of CO2 when they are being manufactured, not to mention the emissions from sourcing and mining the raw materials and then transporting them to the manufacturing plant and then moving the finished products on to the jobsites. Roughly a ton of CO2 is released for every ton of cement produced and a ton of CO2 is released for every ton and a half of steel manufactured. Innovations in the manufacturing processes of these two building materials are helping to reduce those emission amounts, but we’re still a long way off from being able to call them green and sustainable building materials.
This article was originally published in the Fall 2015 Issue of Construction Data Quarterly.