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What Does a High-Performance Building Look Like?

Alan Scott

A recent conversation with a fellow architect prompted this question for me—what does a high-performance, sustainable building look like? Are there obvious clues in the building form, the façade articulation or the materials palette? Or are the green features hidden? Would you only experience it in your improved comfort, or when paying the utility bills? I have seen two ends of the spectrum—feature-less boxes with large window areas that may perform well, but missed opportunities to be even better; and iconic green buildings with sculptural forms, sometimes sporting fins, louvers or even moving parts, that in the end may not have gained the added performance to justify the additional expense. Is there a middle ground?

Should it Show?

I’ve heard from some passionate designers of sustainable buildings that it is imperative that the performance aspects of a building be the primary form-givers. With this thinking, any building with two similar façades that face different orientations has likely failed the test. This point of view is understandable because we know that orientation matters. For example, a south-facing window (in the northern hemisphere) can provide quality daylight and a net energy benefit, whereas a west-facing window is more often a source of excessive heat gain and glare in the afternoon. Likewise, we know generically when looking at metrics for energy, daylight and occupant comfort, that in many climate zones, a building elongated on its east-west axis will outperform an otherwise identical building that is square or stretched north and south.

However, while some building sites are relatively open with unobstructed surroundings, many more projects occur on complex sites, bound by other buildings or unique land features, with limitations due to access, zoning codes and other factors that shape how the program can be manifest on the site. Economic factors (e.g., affordable housing development) and local hazard risks (e.g., high winds) may further limit design options. What then? If a design team can achieve a low energy use intensity (EUI) by optimizing window-to-wall ratios, high-performance glazing selection and envelop thermal performance in a uniform facade, along with right-sizing an efficient HVAC system and providing illumination with a low lighting power density, is that not a high-performance building?

Office tower solar radiation

Office tower solar radiation analysis. Image courtesy of WSP Built Ecology

Making it Count 

Regardless of whether a project team chooses expressive elements or stealth strategies to achieve performance, software tools (e.g., Rhino, Grasshopper, Ladybug, etc.) are invaluable for performing parametric modeling to select and optimize the approach. This allows the quick environmental analysis of building envelopes in their context, looking for the factors that will most influence performance.

The application of parametric analysis in the early design phase provides the architect with feedback on the implications of façade design decisions. These include spatial daylight autonomy (sDA), annual sunlight exposure (ASE), solar radiation, shading effectiveness, and hours of direct sun exposure (at each floor level). It also allows for comparisons of fenestration options including window height, shading devices, glazing selection (coatings, frits, electrochromic glazing), along with their relative impacts on energy, thermal comfort and visual comfort. When coupled with modeling software like IES, this analysis can also quantify the influence of each option on HVAC sizing and energy use. If your design intent is to make building performance the form generator, you need to start with the parameters that really count.

Parametric analysis

Parametric analysis process. Image courtesy of WSP Built Ecology.

Finding the Balance

A parametric model can be used to provide a quick sensitivity analysis of façade options for a single floor of a proposed building, or to evaluate choices influencing the form and articulation of an entire conceptual building. While the designer’s intuition and experience can guide the hypothesis for the best solution, sometimes the complex interplay of microclimate, exposure and project-specific parameters can be deceiving, necessitating a qualitative test of the hypothesis.

My colleagues recently conducted a comprehensive façade study for a new office tower in a dense downtown district. The project was surrounded by other existing towers, so not surprisingly, the various façade design options showed little difference relative to key energy and comfort metrics. The one exception was the southwestern exposure of the upper floors, where glare was identified as a primary concern.

The analysis allowed the design team to explore localized design modifications to the façade to mitigate glare at the specific times that it would be an issue, which could then be expressed in the building form, or hidden in the glazing specifications. The parametric modeling included a sensitivity analysis that revealed which glazing and shading options for the southwest façade provided the best overall benefit. In this case, adding a frit pattern to the glass or specifying electrochromic glazing had significant benefits in reducing EUI and HVAC sizing, and increasing comfort, while strategies such as exterior shading were more limited in their impact.

Parametric façade analysis

Parametric façade analysis. Image courtesy of WSP Built Ecology.

A building design inspired by sustainability goals demands the honest application of elements intended to enhance its performance, to avoid undermining its own integrity with accusations of “all show and no go.” Similarly, an unpretentious building with high-performance aspirations should be able to tell a story of optimization and economy, with all key components designed and specified to enhance energy performance and comfort, while identifying and mitigating potential problem areas (e.g. periods of glare) that could be difficult to fix later as a retrofit. In both scenarios, these buildings represent significant long-term investments.

Parametric analysis tools provide the necessary decision support for architects. Beauty may be in the eye of the beholder, but the proof of performance starts with doing your homework and having the numbers to back up design decisions. What do you think?


Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with 30 years of experience in sustainable building design. He is a senior associate with YR&G, a WSP company, in Portland, Ore. To learn more, visit www.yrgxyz.com and follow Scott on Twitter @alanscott_faia.