Taking Care of Business

Summary: Last week, some readers expressed concern about the energy efficiency of Jeanne Gang’s Aqua Tower in Chicago, particularly considering its exposed slab edges. We bring you some typical letters and Gang’s response.

Re: Site, Materials, and Form Flow Together in Studio Gang’s Aqua Tower

Astounding! Yet so common sense in its reasoning.

Not since Gaudi's Casa Battlo and Casa Mila have I seen a logical response to contextual contingencies that also produces an ethereally poetic and formally convincing structure.

Not having any plans to consider, I wonder whether the interior has a similar driving spirit or is merely a developer's assembly of occupancy spaces.

The ingenuity of reducing the lateral forces resistance by the flowing floor fins is a great bonus. The resulting image is reminiscent of the paper-thin, heat-distributing flakes in a baseboard heater. Big question thus arises, viz.: Despite the wisdom of using them to offer gradated shade from the sun, will the concrete floor fins lose heat to the outside air as rapidly as a finned-tube radiator loses heat to the room? Is there any thing to prevent heat from flowing rapidly through the extended slabs outward in the Chicago winter and inward in the Chicago summer, thus negating the value of the sunshading?

Is the beautiful building really a giant upended baseboard radiator?

—Patrick J. Quinn, FAIA
Albany, N.Y.

Please look at this building and look at a motor cycle engine. Note the cooling fins on the motor cycle engine? See the similarities?

Let’s see—very efficient cooling fins in the winter (exacerbated by windy Chicago weather), requiring more heating. The same fins will act as thermal mass in the summer, soaking up all that sun and releasing it back into the building requiring more air conditioning.

“As with much of Chicago-based Studio Gang Architects’ body of work, sustainability is a primary design focus.” How could you say that about this energy hog! This building envelope will be lucky to provide its tenants and the owner with an insulation value of R-2. This isn’t rocket science, so please don’t sell it as a building with sustainability ambitions. Sell it for what it is: Environment be damned, exercise in art.

—Dan Moon, AIA, LEED-AP
Quality Assurance Manager, Walsh Construction Co./WA
Seattle

Jeanne Gang, AIA, principal, Studio Gang, responds:
Good question.

It is important to shade the exterior side of the glass to reduce solar heat gain. This strategy is highly effective—more so than what can be achieved with coatings on the glass. The external shading of the glass strategy with the slab extensions has a larger impact on energy reduction than the 9 inches of slab exposure to heat loss.

The exposure is 9 inches (the cross section of the slab—no more). In other words, there is no more heat loss in Aqua than any other building with an exposed slab edge. The large terraces do not increase the exposure, which is the point the reader may have misunderstood.

My engineer, Sachin Anand, is working to compile a report comparing the energy savings of the exterior shaded glass vs, slab heat loss on this aspect of Aqua to make it available for others. It would seem like an important piece of information for anyone planning tall buildings in climates similar to Chicago.