LWK + PARTNERS recently won Merit in the Advancing Net Zero Ideas Competition organised by Hong Kong Green Building Council in Hong Kong with a retrofitting proposal for Oxford House, an existing office building in the city. The design envisions to turn the building into an urban forest paradise, in a high-rise, high-density city context.
The goal is promotion mental health and significantly cuts down on energy consumption through active and passive design strategies, bringing the vision of net zero closer to reality. Innovations to upgrade existing buildings into green, energy-efficient structures have the potential to revolutionise sustainable urban development.
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As an illustrative example, the Oxford House competition proposal sheds new light on future urban regeneration and helps us rethink the form of future-ready high-rise developments in the age of climate change. Below are the range of passive and active strategies it adopts to achieve low-carbon objectives while maximising users’ thermal comfort and wellbeing.
Minimising heat gain
The first step for lowering energy use in buildings is to reduce heat gain. The Oxford House proposal adapts to Hong Kong’s densely populated humid subtropical urban environment by making the best use of vertical spaces to reduce heat gain from solar radiation and lower the energy demand for cooling.
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The proposal reuses and converts the existing façade into a green façade with a setback design that also creates a double-skin façade. It sets back the existing façade while leaving the floor slab extent unchanged, resulting in projecting floors that double as a shading device for the floors below. This reduces the need for new material for building shading.
The setback also creates a double-skin façade, which consists of an external glazing, an intermediate cavity and an inner façade. The external glazing provides protection against weather, while the intermediate cavity, spanning 10 centimetres to 2 metres, would act as a thermal cushion with planters for additional shading and solar absorption.
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The inner skin protects against indoor thermal losses and facilitates the control of permeability for natural ventilation. The existing low-e external glazing is reused as the inner skin. To produce a stack effect, which enhances natural ventilation, voids are opened in existing floor slabs to allow for hot air to move up creating negative pressure to draw the air inside.
Pushing back the line for energy consumption area
Air-conditioning is a major source of energy consumption. Pushing back the line for air-conditioned area is a major sustainable design strategy which involves a combination of natural ventilation and auxiliaries – known as hybrid ventilation. In this Oxford House example, the ground-floor entrance space is fully opened up to omit air-conditioning altogether.
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Natural lighting is also introduced to avoid artificial lighting, while a pair of existing escalators is replaced by stair seating to provide both connection between the floors and gathering spaces. A Green Link is proposed to turn the existing connection into a semi open space for a mentally comfortable atmosphere and to cut down on energy consumption.
Cross ventilation is encouraged in common areas like entrances, lobbies and shared corridors, through operable openings and open façades from opposite sides of the building. These are further assisted by active gears to maximise thermal comfort. A solar chimney is introduced to improve the air ventilation in the car park or foyer.
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It typically consists of a black-painted chimney which quickly heats up the air inside, creates an updraft of air and draws it to the outside, increasing the air circulation inside the building and cooling the building. Other energy-saving devices include a combination of big ceiling fans and reflective pools, which improves the thermal sensation of users through water evaporation and ventilation.
Post-occupation evaluation can also help determine the optimal level of water-cooled breeze in a semi-controlled environment. Anidolic light pipes are installed to capture daylight and transfer it to indoor spaces, reducing the need for artificial lighting and meaningfully integrate our natural and built environments. Source and images Courtesy of LWK + PARTNERS.