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Interview with architect Astrid Piber from UNStudio. How to deal with the upgrading of a representative building. The retrofit of the facade and...
Interview with architect Astrid Piber from UNStudio.
How to deal with the upgrading of a representative building.

July 7.2020

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Architect Astrid Piber - UNStudio
MSc in Advanced Architectural Design, Columbia University, New York City, United States
Dipl.Ing. Technical University Vienna, Vienna, Austria. Joined UNStudio in 1998
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If you had to choose three key words to describe the Hanwha HQ project, which ones would you pick?
User comfort, retrofit in place, performative building envelope.
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In the Hanwha HQ project, what is the role of PV? How is it related to the building concept and architecture?
We can frame the role of photovoltaics on three different levels: the first one refers to the client, as Hanwha Group is the third largest photovoltaic producer in the world. When we were commissioned for this retrofit project, we were required to modernize and upgrade the building. Naturally, our suggestion was to install PV on the facades, because on high-rise buildings, the space available on the roof is limited. Moreover, integrating PV on the facades would enable us to include the modules in the architectural concept, while at the same time displaying Hanwha Group’s own products and thus connecting the project to the client’s brand.
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Secondly, using the facades as renewable energy generating surfaces enables the reduction of operating costs, as the energy produced would be used in-situ, and would reduce the CO2 emissions of the building.
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The third and last level is the role of design. We are talking here about a performative envelope. UNStudio developed a facade concept that is fully inclusive and where the façade response to the urban context is integrated. This takes into account the surrounding buildings, the shadowing they create and the orientation of the different surfaces. The new facade also enables the improvement of the indoor climate as, although the structure of the existing building was still working adequately, the technical systems were outdated so it was necessary to include some enhancements. In the retrofit, the technical system is connected to the facade in order to guarantee the correct ventilation of the building, which really improves the user’s comfort and creates a higher level of sustainability for the renovation. The new facade also responds to the program of the building, reflecting the function of each area. For example, the common spaces are characterized by larger openings and their locations correspond with the openings in the surrounding built landscape.
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In the end this specific project can be summarized in three points: branding, cost saving and design. Whilst we used a standard product, it was integrated in the project in a way that appears different. Consequently, it is also interesting for the perception of PV as a simple, standard product that can be used in different ways. It is therefore up to the architect to make it become an integrated part of the design.
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What will you bring of the Hanwha HQ retrofit project to your upcoming works?
What we are seeing now, especially in Europe and in several big cities in Asia, is a new awareness and attitude towards retrofits. It is not always necessary to tear down a construction in order to build a new one. On the contrary, it is sometimes possible to keep what is still intact of the building and remodel the facades and the exterior, whilst integrating a sustainable strategy into this approach. Moreover, for many clients, a retrofit-in-place is actually a more affordable and reliable way to update buildings in need of renovations.
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The experience and knowledge gained during the renovation of the Hanwha HQ is certainly something that we would like to bring to future projects; developing new and very specific approaches in each case. In the end, opting for an onsite renovation is a decision that the owner has to take. In this instance, for the duration of the retrofit, of the 3000 people that used to work in the building, this number was reduced by about 800. Nevertheless, being a representative building it was important that the offices remain accessible, even if they could not be fully used.
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How important is the relationship between architecture and technology in projects of this scale?
We strongly believe in integrated solutions. Of course you could treat technology as a simple add-on, but then it would never be as effective as it can be. That is why we consider the integration of technology in the design approach essential for a project to succeed. The building envelope is not an isolated element, as it is connected to the structure of the building and to what is taking place inside. As a result, the two cannot be separated and consequently, you cannot separate technology from the design of the building.
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Who supported UNStudio in the design and planning of the facade?
Our facade and sustainability consultant was ARUP Hong Kong, while the lighting consultant for the interior and for the facades was AG Licht, a company based in Cologne. Locally we worked with Gansam Architects from Seoul.
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ARUP worked with us in order to define which were the best areas for exploiting solar energy and to find the right balance between the costs and benefits of the BIPV installation. In the end, it was an energy-orientated decision, as we choose the surfaces that were most exposed to sunlight. To find the correct aesthetic, we used different software: Rhino and Grasshopper.
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What was the most challenging aspect to manage?
Initially it was necessary to understand the old building in order to connect the existing structure to the new design. We wanted to upgrade the building and develop a unique design that contrasted with the previous appearance, as this was somewhat out-dated. Our idea was to bring an unconventional appearance to an administrative building, while creating a light and pleasant indoor environment. That was probably the biggest challenge; finding a way within the design to relate such a large building to the individuals that occupy it.
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How did you define the characteristics of the “standard module” and of the “A-typical module”? Which inputs were taken into account? (size, glass type, shading effect on the window pane, etc.). Which tools have you used?
We divided the 3.60m grid of the existing structure into elements of 1.2m width. The height of the element and of the proportion of the sunshade panel varies depending on its function. The highest elements are located in the more public areas, while the ones with the bigger PV elements integrated into them are located on the south facade. We combined them in an ordinated way with the intention of creating a visually continuous façade field.
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The elements on the north facade are slightly different, as they do not have as much depth as the ones on the other facades, where the frames also have an important shading effect. Fine-tuning was also necessary in relation to the framing of the panels, as we wanted to reduce the amount of material used and increase the transparency of the facade.
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BIPV vs “conventional” building components:
a. Since the construct PV project UNStudio is working on new ideas with the aim to implement PV in the building envelope: do you see any difference in your way of work (design, plan, creation, etc.) when dealing with PV/BIPV and “conventional” cladding product (facade technology)?
We worked with a consortium on the PV Construct project with the aim of developing a module prototype. Our arch tech branch UNSense also just launched the product Solar Visuals that instead focuses more on the textures, the colours, the prints and how to create an active facade. The unique aspect of the Hanwha project however is that we could integrate conventional photovoltaics modules into the building envelope.
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We are always looking at other ways of integrating PV in connection to the product or to the architecture itself. When we choose a cladding material we always have to keep in mind the client and their requests. For the building in Korea it was very clear that we were looking at giving the building a new skin and a new appearance. That is why we arrived at discussions about modularity and resolving the identified constraints by way of design focused solutions.
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On the other hand, when we work with more typical products, we focus more on issues that are generally technologically related: such as what is the energy potential? What can you achieve with it? And how does it look?
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b. What do you see as the major challenge for BIPV? What could be improved (in the product/system or in the process)?
One of the criticisms I often hear about PV is that technology can quickly outpace itself. That is why we have to be very careful when introducing technology into a project. In Korea, we were lucky to work with a PV manufacturer as the client, as it is very probable that they will keep up with the technology and upgrade the modules if necessary. In this case, as the facade consists of a modular system, the replacement of the different elements is indeed feasible. However, not every client has the same opportunities and that is why it is very important to understand how the building, with its materials and technologies, is used, how it can be maintained and what the chosen technology means for the future of the building.
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Does South Korea have special requirements in relation to the energy efficiency of buildings? (Building envelope/skin, technical installations, energy consumption, etc.)
Without getting into specifics, South Korea is very focused on reducing CO2 emissions. Since 2002, Korean projects with a GFA that exceeds 3000m2 have had to acquire a G-SEED certificate (Green Standard for Energy and Environmental Design), and the sustainable regulation from 2013 was followed in the case of the remodelling the Hanwha HQ. During the construction phase, the actual energy performance of the facade exceeded the required standards at the time.
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Was there anything that particularly surprised you during the duration of the project? Do you have a favourite memory?
There were many surprises along the way, but what really struck me was the fact that we actually went for a bottom to top retrofitting: two floors at the time and while the building was still in use. We had never done something like that before and, even in South Korea, the Hanwha HQ building was only the second retrofit-in-place to have been carried out. Nevertheless, in the end, it worked really well.
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My favourite memory is probably linked to the first project presentation that we gave to a very large group of people who represented all of the departments of Hanwha Group. They were equally very excited about our ideas. The client’s enthusiasm really supported the design choices and that is why the project went so smoothly.
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How do you plan to integrate photovoltaics in your next projects? Do you favour a certain technology or type of application?
We are very excited about the new product called Solar Visuals, that our arch tech branch UNSense recently launched. It is a cladding material characterized by a high level of customizable aesthetics. The energy generating facade panels are tailor-designed in such a way that they can be integrated seamlessly into the façade surfaces of buildings, optimizing both its form and function. Compared to most current non-printed solar panels, these energy-generating facade modules hold an energy efficiency of up to 85%, with a capacity of 220 watts peak (Wp) per panel. At the moment we have several ongoing projects where we plan to use this product.
See also
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UNStudio website
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Hanwha Headquarters
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Solarchitecture

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