Spark is a state-of-the-art building near Madison’s Capitol –– owned by American Family Insurance. The 158,000 sq ft (14,694 sq m) Spark is home to several hundred of American Family’s 8,100 employees. It also houses DreamBank, a community space dedicated to the pursuit of dreams, and StartingBlock Madison, an entrepreneurial hub fostering Madison’s start-up community, along with the new American Family Insurance Institute for Corporate and Social Impact. Located in Madison’s revitalized Capitol East District, where January lows average 8ºF (-13ºC), it features a sustainable, LEED certified de- sign expected to yield dramatic reductions in heat energy consumption and carbon emissions. Among the innovative energy-saving measures are a 10,000 gallon (38,000 liter) rooftop rainwater collection system, a dedicated outdoor air mechanical system (DOAS) coupled with a geo-exchange bore field, sun shades that raise and lower automatically based on sunlight intensity, and structural thermal breaks that isolate cold exterior balco- nies from the warm interior floor slabs. Balconies: an office building anomaly “This is the first time I’ve done balconies for an office building,” said Joe Lopera, Senior Project Specialist at Milwaukee’s Eppstein Uhen Architects (EUA). “The idea was to give tenants stunning views of the Madison skyline, and encourage them to work on the balconies with their laptops in warm weather.” During frigid Madison winters, however, EUAwanted to minimize the heat loss through the balconies to improve the overall efficiency of the building envelope, a problem solved by installing structural thermal breaks at the line of insulation. In typical balcony construction, thermal bridging occurs where a monolithic slab penetrates the insulated building envelope, allow- ing heat energy to easily escape through concrete and rebar into the cantilevered balcony, which acts as a cooling fin during low- temperature conditions. In addition to wasting energy, uninsulated balconies allow for sig- nificant cold penetration into the building, chilling adjacent interior surfaces. If these adjacent surfaces fall below the dew point condensa- tion occurs, greatly elevating the risk of degradation of materials and potential mold growth in wall and ceiling cavities. Often the risk of condensation alone at the slab-to-wall interface drives the decision to incorporate a structural thermal break. SPARK BUILDING INSULATES HEATED SLABS FROM FRIGID BALCONIES WITH STRUCTURAL THERMAL BREAKS
Thermal breaks prevent condensation, improve thermal comfort, reduce energy demand The design team averted thermal bridging issues at the balconies by installing Schöck Isokorb® Structural Thermal Breaks. Positioned within the building envelope between the interior floor slab and cantilevered balcony slab, they act as continuation of the wall insula- tion through the concrete floor slab. Most of the cross sectional area typically consisting of concrete and carbon steel is now comprised of a high-performing graphite-enhanced expanded polystyrene block that is less than 2 percent as conductive as concrete. Additional energy savings are derived from the module’s stainless steel rebar, which is one-third as conductive as its carbon steel equivalent. Projecting from both sides of the structural thermal break, the rebar is engineered to fully develop into the adjacent concrete components without the need for lapping onto adjacent steel.
The assembly provides the necessary strength and stiffness to sup- port the anticipated loads on the exterior cantilevered slab, while raising the tempera- ture of the adjacent interior slab by up to 34ºF (19ºC), with three results: 1) prevention of condensation and mold growth on adja- cent interior surfaces, 2) improved occupant comfort, and 3) energy savings up to 90 per- cent at the connection. The Spark's five balco- nies contain a total of 148 linear feet (44 lin- ear meters) of structural thermal breaks. Joe
The Spark Building with balconies visible
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november 2020
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