While a great deal of time, effort, and expense typically goes into designing, fabricating, fine-tuning, erecting, and commissioning a high-performance facade, once a building is up and running, the building team is typically on to the next project and the owner assumes the facility is performing as intended.

Photo courtesy of Kirksey Architects

Post-occupancy evaluations are important to ensuring that high-performance facades are actually performing as designed. Such a study was completed for the Energy Center Three building in Houston.

However, due to the complexity and number of systems that must come together in a high-performance facade, more often than not, the system is not performing at its optimal level. A high-performance facade is defined as a building enclosure that employs complex concepts for daylighting, solar heat gain control, ventilation, and space conditioning based on the use of advanced materials, automated dynamic components, and integrated climate controls.

“High-performance facade systems are inherently complex and growing more so,” explains Mic Patterson, Ph.D., LEED AP BD+C, immediate past president, ambassador of innovation and collaboration, Facade Tectonics Institute (FTI), Los Angeles. “They are consequently sensitive to quality issues in design and execution, particularly in their fabrication and installation.”

Furthermore, the facade is the most expensive part of a building, and the building’s energy consumption, daylighting, HVAC, comfort, and sometimes acoustics are highly dependent on it.

“In general, post-occupancy evaluations (POE) are sorely needed as a best management practice for all design projects. With any large capital investment promising multiple attribute returns, it would be unwise not to perform some level of POE and commissioning effort,” says Colin Rohlfing, AIA, LEED AP, vice president, director of sustainable development, HDR, Chicago.

Preaching the importance of POEs, Patrick Thibaudeau, vice president, sustainable design, HGA Architects and Engineers, Minneapolis, explains that they show areas where occupant comfort and satisfaction require engaging building occupants in a process of understanding and improving the overall performance of the building. “The post-occupancy phase of a project is becoming increasingly important since it involves the completed project and the actual workings of the people in the building,” he says.

Photo courtesy of Perkins Eastman

Useful POE information gathered from another K–12 design led Perkins Eastman to reduce window sizing and add an internal lightshelf at Dr. Martin Luther King Jr. School in Cambridge, Massachusetts. The result is that students and teachers rarely turn the electrical lights on.

The Facade’s Interworkings

Drilling into the details of how facades work, Heather Jauregui, LEED AP BD+C, O+M, CPHC, sustainability specialist, Perkins Eastman, Washington, D.C., explains that from a thermal comfort and energy perspective, the more well-insulated and airtight an assembly, the greater the risk that construction and/or detailing mistakes can be made. If this occurs, moisture can accumulate within the insulation and eventually lead to mold/mildew issues or degradation over time.

Furthermore, from a daylight perspective, the facade has a tremendous impact on how much daylight enters a building and how well that daylight is controlled. “The orientation, window-to-wall ratio, window proportions and location, glazing parameters, and shading elements all impact where and how daylight may be transmitted to the interior and how these elements combine to deliver significantly different results,” she says.

“Studying the assembly after construction can help catch potential errors before they may become an issue down the road,” she continues. “This can also lead to a learning opportunity for both the design team to improve detailing on high-performance facades on subsequent projects and for the construction team to improve on how the envelope comes together to minimize potential issues.”

In fact, Jauregui reports that after conducting POEs on multiple past projects, Perkins Eastman discovered that designing to textbook lighting levels may actually over-light interior spaces in relation to occupants’ real-life preferences. This valuable information is currently informing the firm’s designs, as it has revised its daylight targets accordingly.

While key data like this can only be uncovered with POEs, Aulikki Sonntag, Drees & Sommer, Basel, Switzerland, points out that the majority of new-construction high-performance facades, especially those that are custom designed, do undergo significant laboratory testing during early construction phases. This frequently includes a performance mockup and, as required, isolated material testing. “These are typically the responsibility of the curtain wall contractor conducted at and/or witnessed by an independent test lab,” she explains.

Sonntag reports that performance mockup testing often includes water infiltration testing, static with pressure differential; dynamic water infiltration via simulated wind-driven rain; structural testing of wind loads; thermal testing to confirm material and joinery can withstand extreme temperature changes; racking, which is a simulation of building movement; proof load structural, which is 1.5 times the design wind load; and proof load racking that tests cyclic movements and the associated safety factor for the overall design.

“On selected curtain walls, we use infrared cameras to test for bridging and to review if operable windows are working properly with HVAC interoperability,” adds Arathi Gowda, AIA, AICP, LEED AP BD+C, associate, SOM, Chicago.

Additional assessments may include testing the loads induced by window-washing equipment, endurance cycling of moveable components such as shading systems, and cycling of operable elements, which is relevant to maintenance. It’s also important to understand that because high-performing new facades incorporate a large degree of prefabrication, if and when field testing were to reveal performance issues post-occupancy, the ability to address these issues may be somewhat limited, depending on the issue.

“Joinery and anchorage is no longer accessible, and there is no exterior scaffold allowing for field work to be conducted. If a typical condition fails in performance—e.g., air infiltration, water infiltration, or even structural issues—chances for a successful field fix are low,” cautions Sonntag.

“The ability to make any modifications after envelope completion is very limited and expensive, unlike MEP commissioning where you can fine tune the systems after construction,” agrees Stevan Vinci, CET, LFA, LEED Fellow, BECxP, CxA+BE, principal, senior sustainability and building science specialist, building specialty services, Morrison Hershfield (MH), Portland.

With MH’s testing expertise, the firm can help owners sort through the various testing options available and develop a new standard envelope testing strategy for current and future projects.

That said, POEs are still highly recommended, and Sonntag lists a number of scenarios where they are particularly useful:

• When the system has a low degree of prefabrication and the air and weather seals are more dependent on the field labor conditions and ultimate quality of the work.
• There is no repetition on elements, hence there is no typical element to be tested in laboratory which would represent a sizeable percentage of the building envelope condition.
• The system is influenced by other adjacent parts, e.g., acoustic or sound separation via adjacent walls/slabs or intersecting with other wall types.
• The system is not a new construction but works with an as-built condition, e.g., refurbishments/renovations where the as-built cannot be fully replicated in the laboratory.
• The system includes moveable components that are field-installed or might require adjustment in the field and cannot be fully evaluated in laboratory or factory settings, e.g., sunshades/operables and their tie-in into the building control system.
• Components that are related to life safety issues, e.g., electrical components, smoke evacuation, etc.
• The system is technically unique or complex and there is not much historical data available, or the system is an integrated part of the overall energy concept of the building, e.g., temperature flow in multilayer facades or tie-in mechanical system using precooled and or preheated air.

Photo courtesy of Tom Bonner Photography/HGA Architects & Engineers

The results from HGA’s Los Angeles Harbor College Science Complex POE is being used as a benchmark for future projects.