Since the early 1950s, the Bavarian town of Inzell, located about 60 miles southeast of Munich, has hosted hundreds of speed skating competitions—first on the ice that formed over Lake Frillensee, then on an outdoor rink constructed in 1965. More than 80 world records have been broken here, so Inzell was an obvious choice to host the March 2011 World Single Distance Speed Skating Championships.
Location Inzell, Germany (Foot of Falkenstein Mountain)
Annual purchased energy use (based on simulation) 63 kBtu/ft2 (715 MJ/m2); 47% of the energy use is for chillers that make the ice
Annual carbon footprint (predicted) 19 lbs. CO2/ft2 (92 kg CO2/m2)
Cost $46.8 million
Gross area 223,350 ft2 (20,750 m2)
Program Ice speed skating stadium, training facility
TEAM & SOURCES
Low E membrane Serge Ferrari S.A.
Interior lighting Siteco Beleuchtungstechnik GmbH
Roof waterproofing Firestone Building Products
The venue for the contest, however, required an upgrade. The city of Inzell needed space for 7,000 attendees and a roof over the open-air facility to protect spectators and competitors from the winter climate. With a tight, 19-month deadline, Inzell hired Behnisch Architekten to turn its dated rink into a modern, energy-efficient arena.
When the design team first visited the site at the foot of the Falkenstein Mountain, Stefan Behnisch thought it was "sort of a shame" to totally enclose the rink. "It was like this natural amphitheater with the mountains and lake all around it," says Behnisch. "The biggest challenge in such a beautiful setting was to come up with a design that fit and didn't destroy the qualities of the natural space."
The designers wanted the structure to become part of the scenery when viewed from the mountains, and they conceived the roof as the "fifth facade" of the building. "It's more or less flying like a cloud above the landscape," says Andreas Leupold, project architect with Behnisch. An early sketch depicts the building's roof as a floating shell between the mountains and lake. Building on this concept, the firm designed a continuous glass enclosure around the existing rink. "Other ice rinks are completely closed with solid walls all around and no daylight," says Leupold. "We wanted to make the facade as transparent as possible for views to the outside."
Holding up all that glass was a difficult task. City representatives wanted a high ceiling of about 30 feet with no columns on the inner portion of the rink to accommodate spectator sight lines and camera angles during the championship. "Creating a wooden structure to stand 295 by 650 feet is quite a distance," says Behnisch. "It's a huge wingspan, and we couldn't put any columns in there. Structurally, it's a big challenge."
Additionally, the roof had to be assembled above the 400-meter track, an existing two-story building on the west side of the rink, and the newly built cement grandstands. Behnisch worked with Rosenheim, Germany-based engineering firm Rossmann Bau GmbH & Co. KG to develop a plan to mount the entire roof on 40 reinforced concrete columns. The latticed trusses were pre-assembled in two halves, lifted by cranes on the east and west sides, and connected in the air. Laminated timber arches were placed on top of them, and then secondary structural beams followed the shape of the arches to create skylights. "I was praying every day," Leupold jokes. "When the last beam was there and the last truss was in, we were very happy."
Incorporating the skylights and other daylighting strategies without affecting the conditions of the ice—direct heat would soften the surface and slow down skaters—also presented a challenge to the project team. The group solved the facade problem with a roof overhang that provides shading from outside the glass facade, which also has a sunscreen printed directly on the glass with a gradient effect to diffuse whatever light is coming through. For the skylights, "We used advanced 3-D simulations to shape and position each [skylight] opening," says Leupold. The modeling resulted in 17 north-oriented skylights positioned to allow natural light into the arena without directly hitting the ice. These crescent-shaped portholes with ETFE glazing protrude up to 20 feet beyond the roof's surface. From above, they look like gills slit into the sleek white roof surface, formed by a reflective, flexible thermoplastic polyolefin (TPO) roofing membrane stretched over a 16-inch-thick layer of mineral wool insulation.
Traditionally, ice rinks require a lot of energy to maintain pristine skating conditions while providing ventilation and a comfortable ambient temperature for competitors and spectators. Almost half of the total primary energy demand at the arena is used to cool the ice, but a large amount is also needed to dry the air and keep condensation from ruining both the ice and the wooden structural elements. "It seems trivial, but an ice skating rink is actually very complex," says Behnisch. To help minimize energy consumption, the firm sought the services of frequent collaborator Transsolar, a climate engineering firm based in Munich.
The solution was separate airstreams for the spectators and the competitors. "One system sends dry air over the ice, and the second system supplies fresh air to the audience then pulls it up and out," explains Björn Röhle of Transsolar. "The humidity does not touch the surface of the ice, so there's no condensation to reduce the velocity." The displacement ventilation system blows fresh (not dehumidified) air into hollow spaces underneath the concrete prefabricated stands for the spectators. The exhaust heat from the machinery that cools the ice is repurposed to also deliver heat from below to the grandstands.
Just before the world championship, the team conducted a smoke test to determine whether the separate ventilation systems were working. "It worked perfectly. We positioned tubes so well on top of the ice that the dehumidified air is just blowing onto the ice and nowhere else," says Leupold. "It was a relief to see, as we had the world championship right around the corner and no time to fix anything."