The Energy Crisis brought on by the OPEC oil embargo of the 1970s profoundly altered how Americans viewed energy consumption, giving rise to an industry — architectural lighting. In 2018, much more aggressive energy codes are pending, and architects’ design responses to such 21st-century challenges as climate change leave them once again morphing to keep pace with client expectations. The practical bridge between design and operation grows ever more important, and a Texas practitioner must address evolving state and local energy codes in a more proactive and integrated way: It might be time to start rank-ordering human desires.
Much has been written about the evolution of the ASHRAE energy targets, and engineers have made an effort to teach young architectural practitioners what these targets mean — but the big picture relies, first, on an intense focus on collaboration and, second, on the wholesale rethinking of design impacts on the energy profile of the state. One area of concern is curtain wall technology.
The Foggy View
In Texas, despite significant advances in passive house technology for residential, community, and small-scale office design — technology that relies on, e.g., strip windows and rainscreen facades [see, for instance, the Houston Advanced Research Center (HARC) (p. 60)] — the design of larger commercial structures continues to be guided by “old-school thinking”: Floor-to-ceiling windows are still the go-to solution for large office buildings. Commercial brokers use various features of the glass box to sell their tenant clients on the “wow” factor of views and daylight.
At first, it seems hard to argue with their thinking: All manner of research and third-party certifications credit the biophilic glass-box design tactic with improving “indoor environmental quality.” Daylight and views have demonstrable benefits for the people that have them in the workplace, and yet glass boxes present not only energy conundrums, as we will see, but human comfort challenges as well.
For starters, employees regularly shield themselves from the negative effects of their curtain walls — heat and glare. “I always take notice of the percentage of glazing that is covered with closed blinds at any given time in a facility,” says Elliot Millican of ME Engineers. “It is rare to find any amount of glazing that is not at least partially covered within a space.”
If occupants aren’t taking advantage of the entire view afforded by floor-to-ceiling glazing, its cost and its headaches seem hard to justify. The high-performance materials used in such envelope systems increase installation costs at the outset and — no matter how well-designed they are — increase energy consumption over the life of the facility, as well. “It’s a lose-lose scenario,” Millican says.
Once a tenant moves in with their complete complement of equipment, furniture, and office accessories, there is a temptation to treat the perimeter glass wall as simply a fourth interior wall. As the rooms fill up with equipment, it begins to seem natural to put low filing cabinets, credenzas, and other workplace paraphernalia against floor-to-ceiling glass — making all the glazing below desktop level irrelevant for purposes of the sought-after daylight and views. During the day, this baggage is less apparent from outside, but at night, when glass buildings glow, we often see the backlit detritus of professional activity piled up against the curtain wall, an unwanted effect.
Population Growth and Power Supply
And yet, large commercial buildings are essential to the commerce that Texas promotes and attracts. Texans are in a state of perpetual celebration over this dramatic and sustained population growth, both in large cities and in rural areas, and yet this influx cannot continue without relying ever more heavily on a limited resource called electrical power. Do we see concomitant growth in production or distribution from the large central power plants? We do not — neither in coal, nor in wind energy production. In 2017, Texas had a summertime electrical capacity of 73,000 megawatts, with fossil fuels at over 76 percent of that resource and wind at 16 percent. We have a reserve capacity in 2018 of approximately 13.5 percent (megawatt hour demand over megawatt capacity). But, since 2010, with population increasing by 210,000 a year and reaching 27.8 million last summer, the production of all power over that time has increased by a mere 10 percent, mostly in wind production.
A recent wake-up call came in a March 2, 2018 article in the Houston Chronicle in which representatives of the Electric Reliability Council of Texas (ERCOT) noted that, this summer, “Texas may reach an all-time high for electricity demand, meaning customers will have to cut consumption.” If the electricity reserve margin dips below 10 percent, given the inevitable fluctuation of unplanned plant shutdowns and periodic loss of wind power, Texas could become the California of 20 years ago, with its rolling blackouts and widespread discomfort.
Add to this the threat that hurricanes pose to the availability of even that electricity, and you have a problem. We in Houston remember the power outages in the aftermath of Ike, and we have come to appreciate that electricity is not only essential to sustain a climate of business as usual — it is responsible for the very quality of life within the built environment. Lest we forget, regular power supply is what keeps such annoyances as mold and mildew infestations from making life exceedingly difficult for city-dwellers, and potentially hazardous to their health.
Last but not least, in a “semi-deregulated market” where ERCOT can give no incentive to keep power suppliers’ plants on line, we are also seeing demand time charges increase: When you use power during the peak hours of the day, your 24-hour bill is linked to that peak cost.
Frankly, until recently, architects’ myopic (starry-eyed?) focus on the glass-box envelope has led us to expect our consultants, the mechanical and other power engineers, to rectify the challenges our glass-box designs create. As energy performance codes grow ever stricter, passing the problems down the line may no longer be an option. In a recent presentation to our office, an engineering firm revealed the complexity we face: Confronted with a client’s desire for a highly glazed building, say a 70-percent window-to-wall ratio, the firm found that a cost-effective glazing solution to reach 2018 targets for energy performance is not available — unless, perhaps, a triple-glazed fenestration approach is used.
Taking into account the range of Texas climates, floor-to-ceiling glass envelopes that meet pending energy codes will require curtain wall assemblies that are expensive — if they even exist — as well as significant mechanical systems gymnastics.
ASHRAE Energy Codes, the 21st-Century Solution
In 2015, Texas embraced the aggressive energy codes of ASHRAE 90.1, IECC 2015. Concurrently, there has been much discussion within our community about the use of the 2012 International Building Construction Code as a statewide performance alternative after many years of ASHRAE code evolutions. However, failing this shift we continue the predictable upgrade based on the engineers’ organization targets selectively adapted as local and now state code. With the next set of these codes — ASHRAE 90.1-2016, IECC 2018 — coming right up, we will have a lot more work to do to ratchet up metering aspects, lighting, and building envelope performance. Our climate targets also recognize weather shifts: Hotter, more humid weather is expected farther north in Texas — to Dallas-Fort Worth.
“Many of my owners struggle with the implementation and cost of complying with the 2015 Energy Code,” says Mark Seibert of CMTA. “I respond by explaining that the purpose of the energy code is to reduce fossil fuel energy consumption and its adverse effect on the environment. It requires architects, engineers, contractors, and owners to collaboratively work together to produce a sustainable and high-performing building. It prioritizes long-term energy cost savings over short-term construction cost, and by requiring a level of building commissioning, the code strives to ensure building energy performance matches the intended design.”
This is not to ignore the substantial contribution of the many Texas firms that are leaders in the design challenge of energy optimization — through such protocols as the AIA 2030 Commitment, as well as the EPA and other third-party energy efficiency pacts. Such efforts remind us that energy optimization requires an integrated approach with the full design team from the very inception of the project. However, it shouldn’t be only in these third-party-recognized projects that we rethink how we design buildings. In any serious, forward-looking discussion of meeting energy codes, our preconceptions must be thoroughly examined.
There’s an additional wrinkle to using the code to encourage energy optimization. As Seibert puts it: “The code is designed to reduce energy consumption and associated energy cost. This savings typically goes into the owner’s pocket, not the tenant’s.” The broker and his or her client thus have little incentive to promote energy-saving solutions: In the end, they still want their glass box. The architect’s best chance to optimize a building’s energy consumption is at the beginning: in the envelope — in the building’s overall orientation, its facade materials, and (most importantly) in the percentage of glazing to highly insulated wall components.
Leaky Curtain Walls and Climate Change
Modern curtain-wall and storefront glazing technologies are certainly improving, but detrimental implications of their on-site stick-built assembly, with its myriad joinery issues, seem to be missing from our design and lifecycle calculations. Here in Houston, near the Texas Gulf Coast, we are regularly reminded that humid air infiltration is one of the biggest building health and energy issues we face, and it is a common problem in glass-box design — through leakage, and, in older buildings, through single-pane (or compromised double-pane) glazing condensation. In my past practice, I saw additional issues with non-insulated spandrel panels, the failure of gaskets, and non-thermally broken window mullion systems. The latter become radiators as well as leaky barriers to the outdoor humidity — and, over time, humidity’s corrosive effects cause mullion system details to deteriorate. In short, a preponderance of glass can leave a building owner-operator with a cascade of envelope failures down the line.
Within 25 to 30 years of their construction, many of the buildings at the university for which I was part of the operations team presented the biggest challenges involving moisture-induced degradation of the seals and surrounding wall systems. As numerous research studies have noted, high-performance insulation and vapor barriers within solid walls outlast the componentry of window systems.
In focusing on Texas, we might assume we are dealing with heat and humidity, but recently we have experienced freezing weather challenges, as well, due to effects of climate change. The impact of freezing on glass panels, curtain-wall gaskets, and non-thermally broken mullions compromises these systems further. The temperature variation that expands and contracts all these components over the course of a year in North Texas might be as great as 100 degrees. That wear and tear necessitates a vigilant maintenance approach — often the last thing an overwhelmed building operator wants to worry about.
Again, for that expensive glass-box rental space, are we really getting the best effect? Operationally, our window-washing approach has now morphed into a facade maintenance approach. The ultraviolet spectrum is particularly hard on gasket systems, and while newer technology has solved some of these problems on sides of the building without direct sunlight, it has some pitfalls. Often, thermal imaging is required to uncover the weak spots in and around compromised glazing assemblies.
The curtain wall, in particular, has been noted as a source of operational difficulties — not the sort of armature to meet the challenge of long-term climate shift. We inhabit glass boxes from 10 and 15 years ago where the gasket technology is not only failing and requiring replacement, but is in fact exacerbating other issues as humidity enters the building. Furthermore, increased demand for mechanical systems to offset humidity and heat gain means increased cost at the outset and greater operational expense later. Building a glass box, which tends to have the ubiquitous four-side-same treatment, entails that at different times of the day there will be different challenges, be they from cold or heat, on those zones facing different directions. Throw in the human preference for perimeter offices, and you have a real challenge for design.
Technology to the Rescue?
Several newer technologies try to improve performance by means of double- and triple-pane insulated glass units that enclose either a vacuum or argon gas between UV-coated lites. We have also seen spectrally self-darkening glass and polychromatic assemblies of glass with sensory abilities. Curtain-wall hardware is using more sophisticated thermally broken mullion systems capable of withstanding hurricane or tornadic pressures.
Other approaches recognize that each face of a building might warrant a different facade approach keyed to views and climatic issues of solar heat gain and glare. Most Texas curtain-wall facade designs at this stage don’t have the truly cutting edge “internet of things technology” or biomimicry application that might include smart materials and assemblies that “learn lessons from how nature treats them.” (Rather than slowly degrading and requiring greater and greater attention, such facades actually get stronger or smarter with age.)
Such assumptions presuppose that the technology “lasts” the lifetime of the building’s use. The wear and tear might be exacerbated by uneven construction processes. After all, this facade is made of millions of pieces and assembled on a job site no matter the weather. Expecting durable and consistent construction and maintenance of such systems is asking a lot. Building performance issues are exacerbated by age; dedicating top dollar to support operations is not possible; a vicious cycle begins.
Finally, while Texas may be on a long journey to get to the super high-performance energy focus that other states have with their net-zero targets, the demand for high-performance facades attractive to tenants and other users is clearly the place for architects to sharpen their saws in this pursuit. We have an increasing amount of amazing simulation tools and partners in side design that together allow us to start seeking alternatives to the glass-box building. As mentioned above, the rainscreen approach, with strip windows whose wainscot-to-ceiling glazing allows ample views while reducing the overall percentage of glass, offers real opportunities. Simply reorienting a building on the site might be a great start: North-facing glazing with appropriate thermal protection for north winds might make sense, while east and west faces could have less glazing. South faces with protected sunscreens could reduce heat gain intrusion while increasing the longevity of the glazing systems themselves. In fact, most net-zero projects aim for a passive house approach to thermal insulation and anti-heat-infiltration.
As my colleague designers and vendors focus on new solutions, perhaps we can succeed in striking a balance between highly insulated wall sections and windows, justifying the long-term virtue of this balance to our partners in ownership, operations, and leasing.
The question becomes whether we rely on technology or substantively change our design process to recognize lifecycle thinking while considering human comfort. The curtain wall industry is, in fact, very much aware of the challenges we face with floor-to-ceiling glass. Perhaps, as has been the case with the last 30 years of lighting design, the industry itself can develop affordable, across-the-board solutions for Texas buildings. We stand at a crossroads: Do we hope for emerging technology to come along and tackle the energy and human comfort issues? Or do we bite the bullet and rethink glass facades for operational optimization in the life of the building?
Rives Taylor, FAIA, is a principal and firmwide sustainability leader at Gensler Houston.