This German Architectural Firm Shows How Buildings Can Be Part Of The Answer To The Climate Challenge Instead Of The Problem

2023-01-13 01:20:06 By : Ms. Mary PPP

German firm Behnisch Architekten recently completed three projects in the US and Europe featuring a new external fixed sunshade system, all based on the same principle but using different materials, dimensions and geometry. The façade system not only shields interiors from solar heat gain during warmer months, but also lets in beneficial sun during the winter, significantly shrinking cooling and heating loads. At the same time, the screen bounces daylight deep into the interior, while maintaining large apertures with views to the outside. It’s unconventional to use a complex façade grid to both protect a building against solar impact while improving natural daylight into the interiors through the redirection of cooler, stray light in summer. Michelle Lee, architect at Behnisch Architekten, explains.

Harvard University Science and Engineering Complex in Allston, USA, by Behnisch Architekten Curtain Fabric Roll Sheer

This German Architectural Firm Shows How Buildings Can Be Part Of The Answer To The Climate Challenge Instead Of The Problem

Describe the external fixed sunshade system that Behnisch Architekten developed, which you used at the Harvard University Science and Engineering Complex, Agora Cancer Research Pole and Adidas Arena. What is so unique and unusual about this external fixed sunshade system?

The three façades developed in response to an architectural feature that is endemic to Germany. Due to the cultural values of environmental stewardship, strict energy building codes and high energy prices, most modern buildings in Germany feature external sunshading. Usually, these sunshades exist as exterior operable horizontal blinds (aka Venetian blinds), which are lowered on sunny days in the morning to shield the interior from solar heat gain, and raised in the evening or on cloudy days. While cost effective and pragmatic, there are two main drawbacks. Firstly, movable shades use electrical energy to open and close, and furthermore they are a headache for building owners, as the moving parts need constant servicing and upkeep. Secondly, they are mostly constrained to horizontal geometries, meaning they are not designed to target the various ranges of geometries of the solar path, or in order to function well, have to be closed all the way down, which blocks the view and natural daylight.

For Agora, we designed a fixed sunshading system that would perform similarly to these vernacular exterior blinds and developed it architecturally to give identity to not only the exterior, but also to shape the interior spaces. A diagonal skewed grid allowed us to provide shading horizontally and diagonally, depending on the exposure of the façade glazing. Within this diagonal parametric module, the depth of the “fins” or brise-soleil are tuned to optimize blocking the peak sun angles at the hottest times of the year and access to daylight. The system is made of perforated, folded aluminum plates mounted on a steel backup structure, which is attached to a catwalk for façade maintenance. The perforation is to minimize contrast. Since the façades of this building are not vertical but mostly tilted and the building is of a complex shape, we had to calculate and design 14 different shading elements. The façade of the Agora building was our first of this typology and the most complex one. The mesh of the elements was chosen so it would allow a good view of the outside. The width of the mesh is dedicated to the depth of the elements. It is scalable. Together with our engineers from Transsolar and Bartenbach Lichtlabor, we designed it so the spring, summer and fall sun would be mostly blocked, the indirect cold light would be reflected in the depth of the room and the winter sun could shine directly on the glass in order to support heating the spaces.

Adidas World of Sports Arena in Herzogenaurach, Germany, by Behnisch Architects

For Adidas World of Sport in Herzogenaurach, Germany, we developed this concept on a larger scale commensurate with the monumental scale of the building.

For Harvard, we were interested in exploring the sunshades at a finer grain scale. Our project was by far the largest building ever built in what was a low-slung residential, largely undeveloped neighborhood in Boston. Our response to this context was a façade that would speak to the proportions of the human body and have a tactile and fabric-like quality, which would soften the scale of the building and better connect the research laboratories inside to the public realm. In order to achieve this, we developed a few types of modules per solar orientation to create a pattern, which would break up the surface of these large volumes. We also learned from Adidas and Agora that there was a lot of backup structure needed to support these elements, so there was an ambition to make the panels as thin and lightweight as possible. We pushed all the structural anchoring of the elements to the top and bottom of the architectural “volumes”, which virtually eliminated the structure in between the occupant and the screen. We also spent one year of research and development to apply the technique of hydroforming to these components, which resulted in 90 % savings of embodied carbon in the shading material.

All three projects are driven by the careful study of sun angles particular to each climate. If you walk around each orientation, you can see on each of these façades that the shades are more pronounced at certain angles – this is because the shades were designed to target a specific range of sun angles. Also, we pushed not only the technical performance, but how these screens are experienced from the inside and how these façades shape the public realm.

What are the numerical outcomes and performance data that the external fixed sunshade systems of the three projects provide? How much energy can be saved?

For Harvard, our sunshading screen lowered peak cooling loads by 25 to 65 %, depending on the program or use of the space behind the façade and the solar orientation of the façade. Because we reduced the peak cooling loads, we could eliminate the use of air-conditioning in the non-laboratory spaces and install radiant ceilings, which were more energy effective and less drafty than traditional HVAC systems. With Adidas and Agora, we achieved similar efficiency. It is somewhat hard to verify since all three buildings are quite energy-efficient, but also have very different purposes. The main savings are the protection against solar radiation on hot spring and summer days and passive heating support in winter. The advantage compared to other sunshading strategies is you have enhanced natural daylight efficiency due to avoiding tinted windows or closed blinds. You have no movable parts. Considering that the average motor for movable outdoor sunshading is 165 watts, and that you would have on a building like Adidas around 1,000 of these motors, you can imagine how much electrical energy just to operate these is saved.

Agora Cancer Research Pole in Lausanne, Switzerland, by Behnisch Architects

Why does your external fixed sunshade system perform far better regarding overall energy and comfort than any movable sunshading device?

For Harvard, we did not pursue a movable sunshade due to the snow and ice in this northern climate. But comparing the two, movable devices require energy, as described above. Furthermore, one important aspect is the light enhancement. Indirect sunlight is reflected by the elements to the ceiling and thus reflected further into the depth of the spaces behind. Also, movable devices have low tolerance to wind. And Boston as well as Lausanne in Switzerland, where the Agora project is situated, have quite windy seasons. And if you have to adjust your design of the technical equipment to high peak loads just because the sunshading might open in summer, you will end up with far less efficient and more expensive ventilation equipment. Another advantage is that you can naturally ventilate, open windows also on sunny days. With closed Venetian blinds, this is less efficient due to an overheated air buffer between the blinds and the glass.

How do you precisely adjust the grid structure to perfectly respond to a building’s exact location, orientation and environment, with the fixed sunshading of each project being individually designed and tailored to the respective position of the sun and cardinal points?

This German Architectural Firm Shows How Buildings Can Be Part Of The Answer To The Climate Challenge Instead Of The Problem

Two Layers Sheer Blinds Fabric For Harvard, we wrote our own algorithm to shape the geometry of the shade to target the sun at the hottest times of the year without blocking out too much sun, which would be detrimental to daylight and views and solar heat gain in the winter months. For Agora and Adidas, we first also simulated on the computer on 3D models the various situations to find the ideal position, depth and mesh width for each situation. Then, with the help of our engineers from Transsolar and Bartenbach Lichtlabor, we fine-tuned these to avoid glare, minimize contrast and optimize daylight enhancement.