At the Façade Tectonics Institute’s (FTI) World Congress, Sept. 28-Oct. 2, I presented the conclusion of FTI’s work outlining an above-code rating program for high-performance nonresidential façades.
FTI’s research was made possible by funding through Lawrence Berkeley National Laboratory. My collaborators on this work were Stephen Selkowitz, consultant; Tom Bougher, principal at West Monroe; Sophie Pennetier, owner of Digne; and more than 50 stakeholders who provided input.
Service life is one of the most challenging outcome categories that stakeholders requested be included in a program, and a topic that I am digging into in this blog.
Above-Code Program Purpose
The purpose of an above-code façade program is to create a rating system that can be referenced by incentive programs created by utilities or local, state or national jurisdictions. This would encourage the implementation of high-performance façades–higher performance than is business-as-usual in most United States jurisdictions today.
The idea is to encourage the use of currently available, proven high-performance technologies and assemblies, and design and construction best practices so they become more widespread. Achieving widespread adoption reduces the cost of achieving higher performance and positions it for adoption in the base codes.
The anticipated results of widespread deployment:
- Enhanced health, wellness, safety, comfort and productivity for building occupants, including increased passive survivability–saving lives when the power goes out and increased building asset value, energy efficiency and electric grid reliability (see figure 2);
- Economic benefits for the manufacturers, fabricators and subcontractors who have already invested in commercializing high-performance façade solutions;
- Further innovation investment and commercialization, positioning domestic manufacturers more competitively against European imports (see figure 3); and
- Increased speed at which above-code performance achieves reduced costs through economies of scale and migrates to base-code performance.
Scope: Fenestration or Broader Façade-Focus?
The question of a “fenestration-only” scope–mirroring the residential window Energy Star program–or a broader façade focus was reviewed carefully. The clear feedback from stakeholders was a broader façade preference. This is because of the performance degraders that would be missed with a narrow scope, the complexity of a fenestration-only program and the potential for unintended consequences.
Missed performance degraders include:
- Air leakage at interfaces between assemblies would be ignored. Air leakage is one of the most significant energy losses in buildings, and its impact grows as window and wall assembly performance improves;
- Thermal bridging at interfaces and connection points on the façade – These are major energy-efficiency detractors. Indeed, many of these thermal bridges are associated with opaque areas, which are often expected to have higher performance than the windows. Opaque areas often deliver lower-than-expected installed performance due to uncontrolled thermal bridging. Experts have shown that heat loss along interfaces between assemblies or at connection points “can add anywhere between 30% to 500% additional heat loss” onto the clear-field wall performance; and
- Quality management – Commissioning and verification of interface design detailing and installation quality are critical, and would be out of scope in a fenestration-only program.
The complexity and potential for unintended consequences derive from:
- Air-water-structural (AWS) performance overlays complexity – Because it is harder and more expensive to achieve both high thermal and AWS requirements in architectural-grade windows compared to residential-grade windows, an uneven playing field may result as requirement stringency increases. The complex range of fenestration systems–fixed windows, operable windows, curtainwall, window wall, storefront, skylights, etc.–further compounds the challenges; and
- Missing daylighting and views counterweight – Without minimum requirements for providing daylight and views, it is possible that energy-only compliance may be achieved by reducing fenestration area instead of by increasing fenestration performance.
Service Life Challenge
In addition to including daylight, views, lifecycle carbon assessment, occupant comfort and thermal resilience requirements, stakeholders identified long-service life as a key pillar of any high-performance façade. Service life, energy performance and lifecycle carbon emissions are coupled rather than independent performance categories. The longer the service life is, the better the long-term energy and operational carbon performance, and the lower the additional embodied carbon for façade assembly replacement.
Component-level service life expectations differ substantially within an assembly. Examples include sealants and gaskets, insulating glass units (IGUs), and aluminum frames. Understanding what a maintenance item is versus what is a determinant of service life is important. The General Services Administration’s (GSA) fenestration assembly service life determination is aligned to the frame service life, and the IGU plus sealants and gaskets are scheduled as replacement items. Planning time frames for each is given by GSA, but these are not validated service life predictions.
So, how do you assess service life? We can’t wait 50 or 100 years to see how long it lasts!
Façade material choice, detailing and construction impact service life. The CSA Group’s Canadian standard CSA S478 – Durability of Buildings and GSA’s interim core building standard provide frameworks to support design for long service life. Strategies could include:
- Setting a target service life;
- Creating a service life plan to achieve the target. As GSA requires, the plan would be completed during design and updated through construction with justification for assembly lifetimes;
- Integrating a maintenance plan based on a reasonable assessment of assembly and component service lives – Replacement of shorter-lived components without damage to the longer-lived assemblies should be required;
- Completing a water management assessment – Moisture management is key to ensuring façade durability. Water in the wrong place for extended periods can cause mold growth and degradation of materials. Complex hygrothermal analyses can assess condensation risk, long-term water accumulation, drying rates, freeze-thaw risk, mold growth risk and more. Simpler moisture analyses could also be required; and
- Requiring regular as-built performance assessment (e.g., annually) to maintain the façade’s rating. This would identify performance degradation as it begins. Similar to building energy benchmarking, measuring performance during a building’s lifetime can have a positive impact on the willingness to make upfront investments in durable specification choices and construction quality control.
The full report, including recommendations for a fully scoped program and a more narrowly scoped program for initial adoption, will be available later in October at https://www.facadetectonics.org.