Escaping the battle for the wall: defining a high-performance façade

The construction market changes slowly. Transformation in business-as-usual façade performance through new technologies, systems and processes is especially slow because remediation is expensive in the event of post-installation problems.

Also, façade-related energy code stringency is slow to change, often resisted by a fear that higher envelope thermal performance will result in reduced window area and poorly daylit interior spaces with limited view to the outside: A poor compromise between human health and climate change mitigation.

How can market transformation to higher-performance façades be achieved without unintended consequences?

The Carrot and Stick Approaches

As Steve Selkowitz and I described in the recent Façade Tectonics Institute’s (FTI) market barriers study, completed for the U.S. Department of Energy (DOE), there are two main approaches to driving high-performance façade adoption:

• Incentivize the top end of the market to create capacity, knowledge and prove performance (the carrot), and
• Pull up the bottom end of the market through regulation (the stick).

It is also possible to do a better job of regulating at the bottom end of the market:

• Adopting the most recent model codes could substantially improve façade performance. Many jurisdictions are using model codes that are more than 10 years outdated, leaving a lot of cost-effective performance on the table.
• Using holistic cost-effectiveness assessments in which the cost savings of reducing HVAC system and duct sizes are considered alongside envelope performance would support adopting more stringent measures.
• Limiting the degree to which envelope performance can be traded off with lower life expectancy systems, such as lighting, hot water and HVAC in performance compliance paths. This has been done in Seattle, Washington, New York, Massachusetts and more recently, in ASHRAE Standard 90.1. This results in higher installed performance fenestration. These so-called “backstop” provisions cause window-area angst for some, especially given that they are not balanced by a requirement to provide sufficient glazing for daylight and views. Recent attempts to add such provisions for schools and nurseries into the International Building Code have been unsuccessful.

Residential Energy Star Success

The Energy Star program for residential windows, doors and skylights has successfully driven residential energy codes to higher stringency. It has been combined with federal tax incentive programs to persuade millions of homeowners to upgrade their windows. The required fenestration performance was a stretch for manufacturers to achieve, but not too large a stretch. As a result, market adoption rates above 80% were achieved over time. When a new Energy Star performance bar was set, the prior version’s performance was adopted into the base residential energy code.

An Above-Code Program for Nonresidential Building Façades is Essential

One of the most significant barriers to adopting higher-performance façades in nonresidential and multifamily buildings is the lack of an above-code standard for fenestration or façades. This may explain why residential fenestration energy code stringency appears to have progressed faster than commercial requirements.

There are whole-building above-code standards, like Energy Star for buildings, the U.S. Green Building Council’s LEED® rating system and IgCC. While these standards typically deliver good whole-building energy performance (energy use intensity) because of efficient internal systems (HVAC, lighting, etc.), they do not guarantee a high-performing façade, although they certainly can, if designed appropriately.

An above-code program focused only on façade performance would support national, state and local governments and utilities in implementing programs driving critical decarbonization, passive survivability and grid resilience goals. How long can the building stay warm or cool enough to support human life during a power outage? This is becoming a critical question for climate change adaptation. Minimizing peak electric demand is key for electric grid operation, especially as buildings continue to electrify heating.

There is No Definition of a High-Performance Nonresidential Fenestration or Façade

Creating an above-code program for nonresidential fenestration or façades requires a definition of high-performance. It also needs:

• a solid program for certifying commercial fenestration performance,
• validated performance at project-specific sizes,
• more accurate thermal performance ratings for spandrel and
• Three-dimensional modeling capabilities for façade assemblies to capture thermal bridging.

The image below shows the solution roadmap for creating an above-code program for façades developed by FTI for the U.S. DOE.

Several of the foundational items are already underway or have been completed. The National Fenestration Rating Council (NFRC) is launching an updated, simplified labeling and certification program for nonresidential fenestration shortly. It provides for certified performance at both the model and project-specific fenestration sizes. In addition, NFRC has developed an easy-to-use tool that offers project-specific size performance data for any product listed in its certified products directory. Work to improve spandrel thermal performance evaluation is underway, sponsored by the Pankow Foundation, and is expected to lead to more accurate spandrel performance ratings.

The most significant part of the solution left outstanding is the definition of high-performance for non-residential façades.

Creating a Definition for High-Performance Façades

At the end of May, FTI signed a contract with Lawrence Berkeley National Laboratory for a project funded by the U.S. DOE to take the first step in developing voluntary high-performance façade design specifications. Sophie Pennetier, Steve Selkowitz, and I will engage with the FTI community and a broader stakeholder group to gather feedback on the approach and structure for the definition of high-performance façade performance.

We will explore how performance should be considered, for example:

• Should expectations differ across different climate types, geographies (coastal versus inland, seismic versus non-seismic, etc.), building types, and façade orientations?
• How should performance be assessed (by simulation, measurement etc.)?
• What should be the breadth of the criteria underpinning the definition?

A non-exhaustive list of criteria for consideration includes:

• Thermal resilience / passive survivability
• Thermal energy demand intensity
• Thermal bridge mitigation
• Thermal comfort near the façade
• Daylight and views provision / visual comfort
• Acoustics
• Condensation resistance
• Water infiltration
• Natural ventilation / indoor air quality
• Embodied carbon and service life / serviceability / maintainability
• Performance verification / validation / commissioning
• Air infiltration/exfiltration performance
• Wind load resistance
• Windborne debris resistance
• Seismic resistance
• Fire resistance

The project will identify which criteria are the main drivers of performance and balance potential conflicts. We will also identify published standards that can be referenced and already define key elements of high performance. There is no need to reinvent the wheel.

The ability to define high-performance more broadly allows us to balance energy, carbon and human factors. We move away from the fight of window against wall in the narrow context of energy. Instead, we seek a more balanced design approach incorporating the need for resilient, energy-efficient, well-daylit and comfortable spaces for people and the planet.

Watch for invitations to engage with FTI on this project, or please contact me if you are interested in participating at Helen [dot] Sanders [at] Technoform [dot] com.