Glass box architecture: a missed “greening” opportunity
Photo by Thomas Vena on Unsplash
Introduction
During my architectural practice, I designed laboratories, offices, retails, restaurants, and residential complexes, many of which were housed in glazing-clad high-rise buildings. However, despite being a part of the team that designed them the way they were, I still found myself asking “why can’t I let people open their office windows, and who thought stuffing people inside an air-sealed fishbowl all day was a good idea?” Even though there were good reasons for doing so, I still find those reasons baffling, as they hint at a tale of ironic complexity borne from the desires to achieve simplicity.
Regrettably and despite the benefits that high-density neighborhoods yield to reduce overall greenhouse gas emissions from building operation, today’s commercial high-rise building design, construction, and regulatory regime create avoidable consequences toward enjoyable, healthy, and sustainable skyscrapers. Skyscraper is a building typology dominated by “glass box” design ethos, thanks in large part to cheap energy prices and technological innovations—air conditioning—in the early 1900s. While enabling the skyscrapers’ sole reliance on electricity-guzzling HVAC systems to cool, heat, and ventilate indoor air, the dominance of conventional approaches to commercial high-rises require significant market transformation to address their decarbonization challenges, which stem from the way that codes and standards are written and applied, building envelopes and systems are designed and installed, and tasks divided between multiple market participants.
Industry Approaches
Skyscrapers are technical marvels. The amount of specialized knowledge and experience needed to erect one is simply too much for any one person or profession. Therefore, high-rises naturally and necessarily rely on division of labor into distinct disciplines and sub-disciplines, which are then combined with years of extensive collaboration and coordination between the architects, engineers, scientists, and regulators to design, build, operate, and maintain.
Unfortunately, this arrangement is not ideal for a systems-thinking approach necessary to design sustainable buildings toward their holistic decarbonization. There is a continued shift from “multidisciplinary” towards “transdisciplinary” approach, to design ever-tightly integrated high-performance buildings that achieve LEED, WELL, and Living Building Challenge certifications among many others. However, the conventional practice still is for each discipline to work in their silos first and foremost, and then periodically come together to merge their work. This division naturally nurture a workflow and notion that buildings are sum of its parts, for the purpose of simplifying the design integration processes (i.e. not making the already-complex building puzzle more complex). This not only help cut costs from avoided adoption of unfamiliar workflows, but also delineate liability should something go awry.
The latter point—liability—is actually a key reason that most buildings are subtractively designed. For example, buildings’ façades—envelopes—are often designed completely separate from the buildings’ interior, usually by an exteriors consultant that specialize in envelope waterproofing or façade systems. Water has a tendency to get into every crevice where it is undesirable and wreak havoc. Likewise, water penetration into the inner layer of exterior wall assembly (e.g. insulation) or to the buildings’ interior spaces (e.g. office) lead to rust and mold that create unsafe environments for the occupant, while degrading the building’s performance to control temperature due to wet materials and surfaces. These problems are especially prominent in buildings with large exposed surfaces such as skyscrapers, which encourage complete outsourcing of façade design to envelope experts and its subsequent isolation from other building components. Despite this isolation in pursuit of simplicity, other challenges further complicate skyscraper design.
Design Practices
Much of the design complications are in response to existing industry approaches that positively reinforce conventional practice. Even with simplification and streamlining, many building components inevitably involve the work of multiple disciplines anyway and undermine the intended simplicity. The following is a list of most common technical issues that render commercial high-rise buildings’ windows inoperable just to set the context:
Building codes. Commercial buildings are often required to have solid windows, especially for multi-story buildings, due to safety reasons that include accidental falls and items being dropped that could injure nearby pedestrians below.
Mechanical systems. Centralized HVAC systems operate inefficiently and fail prematurely when subjected to conditioning variable indoor climates, and individual control over the operation of windows will create unforeseen indoor microclimates that HVAC systems are not designed to handle.
Façade systems. Operable windows inevitably create complexity for the building’s skin, and common window failures such as wear-and-tear of weather seals result in indoor climate variability that stress HVAC systems, in addition to unintended damage from undesirable elements penetration. Furthermore, all moving parts of windows need to be able to withstand lateral forces (e.g. wind loads, earthquakes), and add further complexity to the structural design of skyscrapers (especially for “supertalls”) by creating unpredictable and uneven wind flows around the building when opened.
Inoperable glazing for commercial properties are valuable especially when taking access security into consideration. However, plenty of residential high-rise towers located in commercial districts like New York City, without safety setbacks typically included for residential towers, already have operable windows and have posed minimal risk to passerby pedestrians (p.s. how often do you read or hear about drop incidents? Rarely). Similarly, plenty of alternatives to conventional HVAC systems, such as high-efficiency heat pumps with mini splits (i.e. individual terminals) coupled with dedicated individual controls, have already existed for a long time in other parts of the world that are only now being seriously considered in the U.S., which pre-empt stress on conventional mechanical equipment. Moreover, having operable windows that give occupants the agency to control their environments lead to productivity and health benefits, arising from natural ventilation and connection to the outside, which add quality of life improvements while reducing energy use and greenhouse gas emissions.
All things considered, the status-quo rationale for requiring high-rise commercial properties to use solid windows, coupled with conventional underperforming mechanical equipment designed specifically for an air-tight envelope system and operated in a completely disconnected manner from the buildings’ interior spaces, is insensible in the era of climate change. The only reason conventional methods are still adopted is because architectural, engineering, and regulatory hurdles to adopting new approaches add time and cost to resolve, which in turn require market transformation to address. Consequently, in most cases, making windows inoperable and conditioning indoor air entirely with mechanical systems is easier and cheaper. Still, there are even more reasons unrelated to technical difficulties that perpetuate all of the challenges listed to this point.
Market Demands
Skyscrapers are built to make a statement. Therefore, discussing how they look and feel is necessarily a part of every design, construction, and regulatory process. A large market driver that encourage the inoperability of commercial high-rises’ windows are desires for natural daylighting and aesthetics.
Plentiful natural daylighting and windows’ operability are two opposing goals. Adding operability adds extra material to the window assembly, including frames that reduce the size of clear glazing, while also adding depth that create shadows. This not only add visual interruptions to the façade that render the building less visually appealing, it also reduces the amount of natural light that reaches the interior space. On the other hand, more and larger clear glazing without operable windows mean more direct sunlight penetration and the associated heat.
In balancing the competing priorities between having a larger glazing to let the natural light in versus reducing indoor air conditioning and ventilation requirements, the former prevailed in the early days of skyscraper boom. Aesthetics play a part in elevating property value. Thus, in a paradigm framed by cheap energy prices (and minimal concerns for the environment), developers opted for higher property value. After all, if operation costs are minimal, who cares?
As I mentioned in my previous blog post, this practice is still ubiquitous in the 21st century: most buildings are developed and sold immediately that render operation and maintenance costs concerns only for the subsequent owners and operators. A possible alternative explanation could be that the inoperable but larger glazing reduced indoor air conditioning and ventilation requirement from reduced need to use incandescent light bulbs in the early 1900s, which are large sources of artificial heat (filaments literally “burn”) that also consume tons of energy. However, this only supports the desire for elevated property value from visually pleasing building façade facilitated by large and uninterrupted glazing. Also, when compared to glass panes and glazing assemblies from the 1900s, contemporary counterparts are much more effective at blocking exterior heat penetration and transfer into interior spaces, which are combined with more effective weather seals that keep the indoor air in and outside air out. This can synergize with high-efficiency heat pumps to further reduce energy demand from increased HVAC system efficiency, while allowing individuals to control their local microclimate.
Closing Thoughts
Buildings are complex living organisms. Many people think them to be permanent, but they are in a constant state of change from tenant renovations, indoor air temperatures changing and adapting, and occupants moving operable components. These interactions naturally render buildings more than the sum of its parts, but the ecosystem that civilizations have developed to design, construct, and regulate these environments have been reductive and simplistic.
While no one answer or solution exist that can correct these past mistakes, we already have multiple ways to solve existing problems that can be context-sensitively adapted to do that. Through policy solutions that initiate, intervene, and enable building adaptations, technological innovations that respond to the changing climate, and enforcement mechanisms that ensure meaningful progress, we still have a chance to correct past mistakes and mitigate worst possible environmental outcomes. We need to adopt all these measures to drive market transformation, so that future high rise towers are designed, constructed, and regulated with occupant and environmental health in mind toward decarbonization.