in pursuit of energy efficient minimalism
In 1996, the German government decided to move the Umweltbundesamt (Federal Environmental Agency) and nearly 800 staff members to the city of Dessau (DE). The UBA is a little like the Environmental Protection Agency, except with actual teeth. After much deliberation, a master plan was drawn up with the proposed site in Dessau’s gasviertel (gas quarter), adjacent to the hauptbahnhof. One of the initial steps for this exemplary demonstration project was to site the building on a contaminated brownfield.
This office is yet another project realized through an open competition, held in 1998. The solution proposed by sauerbruch hutton placed the building to the east of the site, allocating the western half to a public park.
The parti is an office building with a double-loaded corridor, deformed to create 2 separate atria. An open atrium to the south marks the public areas and a closed atrium to the north is surrounded by the interior ring of shared offices and conference rooms. Individual offices are situated along the exterior. The ensuing solution offers a multitude of interesting perspectives and enlivens the interior corridors. A library south of the ‘snake’ connects the new building to an existing warehouse, and a cafeteria is located across the public park towards the tracks.
The UBA is a reinforced concrete structure consisting of slabs, columns and stairs/elevator cores. Highly insulated, prefabricated timber panels line the exterior and ‘interior’ walls around the atrium. The atrium roof is a filigree construction of glass and steel.
The exterior facade is about 40% glazed and an elegant composition of double-paned windows, larch spandrels and safety glass with enamel finishes in 33 different shades – corresponding to adjacent elements (ponds, trees, warehouses, etc). This polychromic frivolity, a hallmark of sauerbruch hutton projects, creates a dynamic effect as one walks around the building. Through an interesting technique, the double-pane larch windows (U-value=0.80 W/m²K, or R-7) are modified by a third pane of glass held off the exterior of the window frame. Blinds for controlling daylight and solar heat gain are installed in this interstitial space. Adjacent to the wood windows are aluminum louvers used in conjunction with motorized vent panels to flush the building at night. In the atria, where light is much softer, facades have a significantly higher percentage of glazing.
As students, we were enthralled by naturally-lit industrial spaces (train stations, warehouses), and so we really dig the way the UBA plays off the industrial heritage of the site. The atrium’s fully glazed sawtooth roof follows the curvature of the building. Polycrystalline photovoltaics are integrated into the southern faces of the sawtooth, while operable panes on the north faces are part of the building’s ventilation system. PVs and solar water collectors can also be found on the green roof over the offices.
The UBA employs a number of strategies for heating and cooling:
- A narrow floor plan assures almost every space is naturally lit.
- Operable windows allow user control and provide natural ventilation for nearly every space.
- The atrium acts as a climate buffer and plays an active role in regulating temperature as well as outside noise from the adjacent train station.
- At only four stories, the building is fairly compact, achieving an S/V ratio of 0.34.
- Clay bricks are used for dividing walls between offices to increase thermal mass, thereby regulating the interior temperature.
- High levels of insulation prevent significant heat loss or gain. The roof has over 12” of insulation and achieves a U-value=0.13 (R-44), while the ground slab has a U-value=0.35 (R-16).
- Additional heating and domestic hot water is supplied via CHP.
- Groundwater is used as seasonal storage (look for further discussion in our next post)
- Night cooling is achieved through the use of motorized vent panels at the facade and venting warm air through the atrium roof.
- An earth-air heat exchanger preconditions outside air through over 5km of tubes, allowing air to be cooled in summer and heated in winter.
Materials with high embodied energy, high CO2 emissions and hazardous substances were excluded. In lieu of aluminum, tinned copper is utilized for flashing and sills – we’ve never seen this but are interested to hear if anyone else has. Instead of rigid insulation, which has a very large PEI, cellulose insulation was incorporated into the prefab exterior. The larch rainscreen is highly durable, has a low embodied energy (especially compared to metal or glass), is highly resistant to rot and was economically advantageous over other systems. The factory for the prefabricated panels was located less than 250 miles from the site.
With a heating demand of 38.5 kWh/m²a (12kBTU/ft²/yr), the UBA doesn’t quite reach passivhaus standards or the planned goal of 30 kWh/m²a. However, the primary energy of 73.1 kWh/m²a (23kBTU/ft²/yr) is significantly lower than the PH maximum of 120 kWh/m²a (38kBTU/ft²/yr). Since the energy for heating in commercial buildings is much smaller than for lighting, this seems to be a wash. We feel this green gem sets the bar rather high, and sauerbruch hutton prove (yet again) a well-designed environment doesn’t have to be sacrificed for energy efficiency.
- Architect: sauerbruch hutton architekten, Berlin
- Mechanical: Ingenieurbüro Zibell Willner und Partner
- Structural: Krebs & Kiefer
- Contractor: Harms & Partner (who also built the GSW & photonikzentrum by sauerbruch hutton)
- Construction cost: €63,000,000 ($83,500,000)
- GFA: 35,765 sm (385,000 sf)
- cost/sf ≈ $217/sf
- completed: 2005
- UBA Energieausweis (pdf, German)
- Deutsche Bauzeitschrift article with details (pdf, German)
- betterbricks writeup (pdf)
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