The Issue
A 45-year old building needed a serious upgrading to become code compliant. The client was faced with two choices: 1) Demolish the building and rebuild or 2) Perform a deep retrofit of the building. The retrofit option was chosen.
Our Approach
We were engaged as the Environmentally Sustainable Design (ESD) Consultant with a clearly defined scope of works in four areas:
Building Performance Simulation Reduce the building energy consumption by more than half, namely from 211 down to 100kWh/m2/year or less
Design development of Integrated Envelope system With special focus on redesigning the long and heavily shaded West-facing facade, to enhance its role as the primary source of views and daylight
Occupant Well-being Enhance occupant well-being, as some rooms were unacceptably cool with measured temperatures down to 16 degree Celsius!
Compliance with Green Mark and international standards The highest green building certification, Green Mark Platinum, was pursued for this project
Our approach was to take part in a series of design charrettes with the retrofit design team and the client. To drive the design decision process was aided by our building performance computer simulations, particularly for the following three design issues:
(1) Facade retrofit
An interesting idea was pursued for the retrofit of the heavily shade West facade: To dismantle the shading louvers and reuse them in the creation of a new facade screen for the building that would offer glare protection, ensure daylight and views, and be aesthetically pleasing. In this connection, it is relevant to note that the retrofitted building is housing the Department of Architecture at the National University of Singapore (NUS).
(2) Hybrid ventilation An alternative to conventional air-conditioning, is to achieve thermal comfort for the building occupants through the use of hybrid ventilation, which combines ceiling fans with a higher temperature set-point for the air-conditioning system. While this approach to thermal comfort works intuitively and on paper, the design team faced a good deal of skepticism from the end-users. As such, a classroom was retrofitted for hybrid ventilation for demonstration purposes and for collecting comfort data on actual building occupants before implementing is wide-scale for the project.
(3) Energy optimisation We used our detailed building energy simulation software, IESVE, to analyse the effect of different energy optimisations for the building. Particularly, the effect of the hybrid ventilation and its 100% outside air rate without any recirculation was studied. But also the effect of efficient electric lighting, and the introduction of occupancy sensors to control the building systems, for example, switch off the lighting and air-conditioning when the spaces are unused.
Our Findings
The project was officially launched on 2 February 2023. The first full year of building performance data for SDE3 building during operation has been collected, and the results are impressive.
(1) Energy efficiency
A measured 5-fold reduction in the annual energy consumption of the SDE3 building
is very impressive, especially considering that the measured energy savings come entirely from energy efficiency and conservation, and not from the use of renewable energy. On that note, the university has recently obtained funding for installing solar photovoltaic panels on the roof, which will make it a ZERO energy building.
The main contributors to the energy efficiency in the building retrofit were:
Hybrid ventilation Instead of cooling the buildings with regular air-conditioning with a temperature set-point of 23°C, but often dropping lower down, the cooling system was changed to hybrid ventilation. Hybrid ventilation combines slow moving ceiling fans with light air-conditioning, where the air temperature is kept between 26-27°C. The higher temperature saves energy while keeping the occupants thermally comfortable
Efficient Cooling System The building scrapped its old chillers and was instead connected to a highly energy efficient district cooling system (0.65 kW/ton efficiency) at the university campus.
Energy Management System The building was equipped with a grid of occupant sensors that allowed the building systems (lighting, ceiling fans, air-conditioning) to switch off, when nobody was around. Such effective energy management was only possible thanks to the hiring of a skilled and dedicated energy manager.
(2) Occupant Satisfaction
The SDE3 building was built in the 1970s and its windows were heavily shaded and heavily tinted. As such, virtually none of the indoor spaces were daylit and the views were limited to a narrow strip below the heavy shading:
To enhance the building performance and the occupant experience, the facades were redesigned and replaced with an aesthetically pleasing high performance façade. The resultant “butterfly façade” not only helped to unleash the beauty of the 45-year old buildings (aka the 'beauty from the beast' concept), but it also ensured better daylight and views out for the occupants. No easy task, as the main façade faces West, and hence, is exposed to low angle sun on a daily basis. The resulting West façade design consisted of a 3-meter long lightshelf, which effectively shades the indoor spaces from the setting sun until 6 pm, while also reflecting diffuse daylight up to the ceiling soffit and further into the space.
Occupant surveys before and after the retrofit showed a remarkable jump in increase in satisfaction with the indoor environment, namely up from 40% (before the retrofit) to 90% (after the retrofit).
(3) Embodied Carbon
A 7-fold reduction in the embodied carbon was achieve by this project by choosing retrofitting instead of tearing down and building new:
By retrofitting SDE3, a much smaller amount of building material was needed, mostly from replacing the MEP systems amounting to a carbon footprint of 59 kg CO2 per m2 of building, as opposed to a 7-fold higher carbon footprint of 417 kg CO2 per m2 insofar the old building had been torn down to make way for a new building.
Conclusion
The successful retrofit case study of the SDE3 building has achieved remarkable environmental results, namely a measured 5-fold reduction in energy consumption, a 7-fold drop in the material carbon footprint and a doubling of the occupant satisfaction with the indoor environmental quality. Moreover, with the striking golden façade screen, the building emerged as a beautiful butterfly, it reached 'beauty from the beast'. A true testament to the power of retrofit.
Acknowledgements: This ambitious retrofit project was the brainchild of Nirmal Kishnani (NUS), Heng Chye Kiang (NUS), Wong Yunn Chii (NUS), Erik L’Heureux (PhD) FAIA (NUS) and Wolfgang Kessling (Transsolar KlimaEngineering), who set the stage and design direction for the project. During the project design and implementation stages, we had a great collaboration with architect Erik L’Heureux (PhD) FAIA (NUS) and his team with CPG Consultants on all architectural matters, especially the beautiful and functional facade design, and with WSP for MEP matters. Great credit goes to Lam Khee Poh (NUS) and Giovanni Cossu (NUS) who both worked tirelessly to deliver the project to completion, and the number of other professional, who enabled the success of the retrofit project. Lastly, the highly skilled and dedicated energy manager, Bertrand Lasternas (NUS), did an excellent job energy-optimising the building during operation while working to integrate performance with the design direction. For the full project team, please go to: https://www.ien.com.my/projects/nus-school-of-design-and-environment-block-(sde1%263)
A shorter version of the above article was published in the GreenRe Bulletin, Issue 10, Dec 2023, page 38-41: direct link: https://www.greenre.org/assetuploads/files/Issue%2010%20Dec%202023_updated_compressed(1).pdf or read/download article below: