@TU Delft. Sun Responsive façades for EWI

Part of the Master course Delft Seminars on Building Technology, this project consists of a redesign of the EWI Building in Delft. The idea is replace the structure, façade, and climate concept as if the building were build today. Below you will find the project description that accompanied the presentation.

For a long time keeping the original, hybrid steel and concrete structure of EWI was under consideration. Yet over time the existing structure was found to be too rigid; both the size of the offices and the location of the hallway and cores was found to be lacking. The original interval of 4050 mm was deemed unpractical and was replaced by a 5400 mm interval . This new interval could better accommodate larger offices, fit underground parking and be divided in useful dimensions for the façade. Inspired by the integrated Holcon floor system of the Villa Flora reference, as designed by Jón Kristinsson, the concrete structure could now be activated and used as an integrated ventilation system within the floor. Lighting could also be incorporated within the floor system. To access and adapt these fittings the Holcon system requires access panels along the full length of the floor. Besides that, within the loadbearing façade elements, or portals, a cavity is left to connect ducts vertically. Not having to leave space for vertical duct shafts means a higher flexibility within the office space, but a more rigid façade. The façade portals are interconnected across the building and the extreme corners of the building further stabilize the building around the elevator shafts and stairwells. Since the objective was to keep the silhouette of the EWI building, an element width of 3 times 5400 mm was chosen for the depth of the offices; a size comparable to the current depth of the building. The new 16200 mm depth is bridged by a single floor element that allows the before mentioned access hatches to placed at 1200 mm intervals across. The 600 mm by 600 mm hatches are made of a concrete and fibre mesh and they require the wooden floor covering above to facilitate access. Through little removable panels one can access the ducts underneath. Since both the wooden floor and the concrete finished ceiling are hard materials, the wooden floor has been elevated slightly to improve the acoustics.

MSc 1 - AR1A075 A1

The main ambition of the redesign of EWI was addressing the sun glare and its overheating problems, combined with the wind turbulence issues that EWI currently suffers. Inspired by sun adaptive systems like that of the Institut du Monde Arabe, or that of the Al Bahar Towers the idea was to create a façade that would adapt to different circumstances. Yet as some of these systems, through their complexity, required a lot of moving parts and maintenance, the concept was to use a little moving parts as possible. Taking reference from projects such as Bloom, the designed façade uses thermo bi-metal sheeting that can open or close as temperature and solar glare increases. The bi-metal alloy combines two sheets with different thermal expansion coefficients; depending on the heat generated by the sun on their surface, they either expand or contract. This way, there are no moving parts involved in opening or closing the sun shading. To protect the thin sheets from the wind they have been placed behind a secondary façade of curved glass. The secondary façade also acts as a rough surface reducing the wind speed across the façade. Behind the second skin a corridor provides access for maintenance. To soften and absorb part of the sunlight, a wooden materialisation has been chosen for the access walkway floor and the inner façade. Yet the walkway remains open to allow the air to rise. Due to the significant load of the curved glass, a supporting laminated console system transfers the load of the second façade to the main concrete structure. For a time using a steel support structure was under consideration, yet a laminated wood structure would improve the overall feel and reduce the possibility of thermal bridges significantly. To allow the curved glass to expand and contract, it has been attached with sliding screws. On a similar note, the bi-metal sheets have enough space to bend, both vertically and horizontally.

MSc 1 - AR1A075 A0

The previously mentioned sun responsive, second skin façade is the main driver of the climate concept; not only does the façade shade the sun, it also acts a solar chimney allowing it to preheat the air. Aided by a venturi wing on the roof, as seen in the reference of the GSW Building, both the east and west façade have a natural draft upwards. The Holcon floor system allows the system to cross ventilate the air, from façade to façade. To take maximum advantage of the heat inside the structure heat exchangers are placed near the façade openings. Thus the air is, if possible first preheated by the second skin cavity, and then secondly heated by the air already existing the plenum of the Holcon floor. At the office level, the space in between floor elements is used to extract the used air, whereas fresh air is introduced through special openings in the floor. Both the ceiling and floor slabs are concrete core activated, the floor being the higher temperature system for user comfort. The core heat is mainly generated by solar collectors on the venturi roof and stored for seasonal use. Varying from season to season, hot or cold water is stored in two different aquifers in the ground. When needed, these are coupled through a heat pump to further reduce heat loss. In winter and summer the system can therefore heat or cool the building if necessary.

MSc 1 - AR1A075 Winter Scheme

To the original group research question, how to liberate EWI from the negative aspects of the natural forces upon it, a personal fascination was added: how to created a self-regulating, low-tech sun shading façade? As mentioned before, most sun adaptive or sun responsive façades require high maintenance due to the number of moving parts. By using the innovation of thermo bi-metal sheets that require none, the intention was to provide a different solution. In practice however it mas more complicated than that. The bi-metal sheets are still in the experimental phase and, particularly in their current form, not highly suited for architectural use; the thin sheets suffer greatly from wind distortion. For that reason the designer of Bloom is currently further developing the sheets by placing them within glass protection. That, combined with an interesting lecture by Nijsse provided the inspiration for using corrugated or curved glass for the second skin façade. It would hopefully kill several birds with one stone: reduce wind speed, protect the sheets and create a solar chimney. As a consequence however the support structure became a lot heavier than first anticipated. Through the group interaction various interesting ideas were collectively developed and implemented, in particular the case with the Villa Flora and the GSW project that delivered many solutions. All this hopefully results in a more user friendly and comfortable façade than the current, existing one: windows can finally be opened and most of the glare and overheating has been stopped, without having to push a button!