Façade Tectonics 2015
by Claire Maxfield, Director
Glass: a love affair
The reasons for our love of glass are surprisingly wide-ranging. First and foremost is novelty: a design to push the boundary of technical production and use glass in new ways. On the other end of the spectrum are several pragmatic reasons: low cost, the ease of off-site production (of curtainwalls especially) and of single-trade envelope construction, and the relative durability of glass. We love the metaphor of transparency (e.g., a transparent corporate culture) and the idea that more glass will give us a greater connection to the outdoors. We love the idea of erasing our architecture completely, and in fact a new project in South Korea aims to do just that using glass-embedded LEDs tied to projectors behind the building, so that the building will display an image of what lies behind it.
Our love of glass also proceeds because of – and in spite of – misunderstandings about the sustainability of highly glazed buildings. We confuse the need for useful daylight with having more daylight; we think that if a connection to the outdoors is good, more transparency must be better. We think that because our commercial buildings are internal-load dominated, that the envelope performance does not matter.
Glass, universalism, and sustainability
Our fascination with glass and the push for more transparency has led us towards all-glass buildings around the globe. Highly glazed buildings are popping up in every nation, climate, urban context, and a wide array of building programs. The difference between the design of the envelope for a commercial tower in China and a high-end residential building in Seattle is surprisingly small, despite vast differences in culture, politics, climate, urban context, program, and even the method of architectural production between the firms that produce these buildings.
The long history of transparency and glass within buildings has been documented well by others and will not be repeated here. But it is important to note that the rise of all-glass buildings, especially curtain wall envelopes, is strongly related to the history of air conditioning. Air conditioning is what made the dream of all-glass buildings habitable and therefore possible in practice. As we strive to reduce energy use and design sustainable buildings, we take aim at mechanical systems; but to address the problem fully we must also re-assess the viability and appropriateness of all-glass envelopes, which cannot function without those same mechanical systems.
This globalization of similar all-glass designs is a critical issue for sustainability within the built environment and our ability to reduce carbon emissions. Even with today’s high-performance glass, glazed envelopes usually perform worse than other envelopes in terms of energy use , carbon emissions, thermal comfort, and visual comfort. Glass is a poor insulator which leads to higher heating energy use and wintertime thermal discomfort in cold climates; in warm climates it admits solar gains, leading to high cooling energy use and summertime thermal discomfort. Excessive glass creates high contrast between the bright building perimeter and darker internal spaces, and low-angle sunlight causes glare. Careful façade design can mitigate these problems, but those strategies must be carefully tuned to climate, orientation, and program. This attention to the specifics of each building and site is not common, judging from the uniformity of recent glass towers in recent years.
The prevalence of all-glass towers is also a symptom of a larger problem of universalist design, an idea which was championed in the modernist era and is particularly inappropriate for current times. Universalism posits that a highly engineered, efficiently manufactured design can be deployed everywhere in equal measure, negating cultural or environmental differences. Our current fascination with all-glass design is similarly based in a fascination with advanced engineering and global application of a single design solution. Even reactive post-modernism , which rejected most modernist thinking, held onto this idea of cultural uniformity. The post-modern retreat to historic forms was based on the idea that familiar forms held symbolic meaning, a “language of architecture” that spoke to the masses . This assumed that the public read these forms in the same way and associated similar meaning with them; usually western forms, meant to convey conventional Western ideas of family, institutional dignity, and so forth. Contemporary practice has struggled to find a suitable way to recognize our pluralistic society, where a single reading of architecture is unlikely and there is be no common ‘language’ of architecture that can be universally understood. As Western architects practicing globally, it is imperative that we acknowledge this pluralism, and not retreat back to the view that one architectural attitude is correct in all places. Therefore we cannot adopt the position that maximum transparency is both understandable and appropriate in all places.
Critical regionalism: a reintroduction
In 1983, Kenneth Frampton introduced a thesis called “Critical Regionalism;” this theory may be in need of reintroduction today. At the time, architecture was in the midst of post-modernism and the conflict between modernism and post-modernism was still being resolved. Critical Regionalism refuted them both. It rejected the fundamental placelessness of modernism, which was based in an engineering mindset of efficiency and universalism. It also rejected the prevalent strain of post-modernism (which was really anti-modernism), harkening back to the familiar and nostalgic forms of previous eras.
Architecture can only be sustained today as a critical practice if it…distances itself equally from the Enlightenment myth of progress and from a reactionary, unrealistic impulse to return to the architectonic forms of the preindustrial past. [It] has to remove itself from both the optimization of advanced technology and the ever-present tendency to regress into nostalgic historicism or the glibly decorative.
Critical Regionalism proposed a third way which was neither universal nor nostalgic, but required that architecture respond to its context. Rather than reference vernacular forms, however, Frampton proposed that we find ways to respond to regional conditions such as topography, light, temperature, and urban context. By making these local conditions generative, one was inherently creating a distinct identity; a specific architecture; a sense of place. For example, rather than flattening a site to create a generic buildable surface, one could terrace the site and thereby create a connection to local geologic history while also producing a building with a more particular identity. Similarly he uses the example of daylight in museums, that resurrects local light conditions in which the works were painted, rather than the universal application of electric lighting which makes all museums homogeneous.
Frampton was talking mostly about a psychic connection to a place, its history, and the local conditions that spawn creative diversity. However this idea of creating ‘place’ is clearly related to current concepts of sustainable design, which is predicated on climate-responsiveness. Though it is rarely discussed in these terms, the process of sustainable façade design has its roots in critical regionalist ideas. In practice as a sustainability consultant, each project indeed starts with an assessment of the factors inherent to the specific site; in essence, we establish the elements that define a sense of place. ‘Place’ includes the local climate (temperature, humidity, insolation, wind speed and direction, psychrometrics, sky conditions, etc.), the immediate context (adjacent buildings, landscape, and topography that may block or exacerbate climatic factors), the building’s program and interior space planning, each project’s primary sustainability goals, and each project’s architectural agenda. Taken together, these factors establish the conditions for the envelope design, and what will make this envelope distinct from the next. These factors produce wide differences across Atelier Ten’s portfolio; they both generate and respond to a unique sense of place. They also respond to local conditions in a stylistically abstract way, without necessarily resorting to a neo-vernacular approach.
Critical Regionalism is therefore a useful framework for assessing glass in buildings because it requires us to look not just at building performance, but at the cultural relevance of the highly glazed design. As part of our sustainability mission we must address the underlying idea of universalism that begets highly glazed buildings.
Case study: transparency, place, and sustainability
The case studies below will examine the process of establishing ‘place’ or context in the sustainable design process, and how the resultant envelope uses transparency and glass in a meaningful and site-specific way.
Salt Lake City is a place of extremes. In summer it is extremely hot with strong solar insolation. In winter it is very cold, and it is comfortable (as defined by ASHRAE) for few hours of the year. In addition to these climate factors, the L.S. Skaggs Pharmacy Research Institute in Salt Lake City has a distinctive site: it is a gateway to the health sciences campus; it has an expansive view of the campus on one side and a close-up view of the Wasatch Mountains on the other; it is attached to an existing 1960s science building and knitting the two buildings together into a coherent whole was a challenge. Last but not least, the laboratory program and user preferences lend themselves to regular, open lab modules combined with small cellular offices.
Taken together, this project has so many aspects of ‘place’ that it is difficult to decide which ones to respond to, and how to do so in a coherent manner. As the design phase began it was important to clarify which site and climate factors would drive the design. Traditionally laboratories are internal-load dominated, which means that the internal functions and HVAC systems determine energy use much more than the building envelope. This often leads to a disregard for climate in lab façade design, which in turn leads to all-glass labs. However this line of thinking represents a misunderstanding of the many sustainable design aspects that must be considered, and a lost opportunity to create a true sense of identity.
Program drivers for envelope design
Glazing types to address daylight, solar gain, heat loss, and glare
External shading design for solar gains, thermal comfort, and visual comfort
From a practical perspective, the building’s southwest orientation, together with the extreme climate, meant that the façade has to respond to many factors: solar gains in summer, conductive heat loss and thermal comfort in winter, year-round glare from low-angle sun, and daylight access and distribution. The resulting façade is a highly nuanced response to both the performance objectives and need to create an architectural sense of place. Though the initial design concept included all-glass facades, the final design uses transparency carefully and where it will have the greatest spatial and environmental impact.
Heat loss through envelope conduction can only be addressed by adding insulation, and to avoid thermal comfort “cold spots” this insulation must be evenly distributed in occupied spaces. Therefore the amount of vision glazing on the primary façade is reduced to 34% while the area of insulated spandrel panel was increased. On secondary facades the glazing is reduced even further, and cavity-wall insulation provides an R-24 assembly.
Solar heat gains are mitigated in several ways, again starting with reduced glass area. External shading incorporates mesh screens parallel to the façade along with smaller vertical elements. The parallel shades are held off the façade which means their shade is cast lower, over the view portion of the glass, without blocking the view itself. Fritted, low-e glass also reduces solar gains.
Useable daylight is often confused with maximized daylight. However too much daylight near the façade can create high contrast compared to the interior spaces and is often simply too bright for day-to-day work. The goal of the façade design was to provide the right amount of daylight for dimming electric lights and creating a visually comfortable workplace. Creating usable daylight started with using the right amount of glazing and positioning it correctly in each office. The external shades block direct sun but allow indirect light into the space, creating evenly-distributed daylight conditions. Bright interior finishes bounce light around the room. Daylight simulation was used to determine precisely where there would be useable daylight, and therefore where it was worth the cost to install daylight-responsive lighting.
To promote visual comfort, both the envelope and interior design were considered. Reducing the glass area and providing external shading reduces the amount of time occupants can see the sun directly, improving comfort. Turning desks towards sidewalls meant that no one looks directly out the window in the afternoon, nor would they see veiling reflections from the window on their screens. Bright interior finishes helped distribute light around the room, reducing contrast. Finally, interior operable shades could be used for those times when glare was still a problem
Taken together, the need for spandrel, fritted glass, shading panels, and solid wall allows the architects to create a patterning on the southwest façade. The result is a textured surface that introduces subtle color shifts that add depth and variation to break up the mass of the building. The façade’s patterning responds to the use of space behind the envelope, thereby registering the function and occupancy of the building in an abstract manner. The shadows, brightness of the frit, and reflection and transparency of the glass changes over the course of the day as the sun moves, thereby avoiding a single, static image of the building and instead providing a dynamic impression though all elements are fixed.
Transparency is used to amplify the translational research function of the building. While the southwest façade uses vision glass to express the regularity of office functions, the north and east facades respond to the spacing of lab benches. Lab users can see through the entire mass in narrow slots aligned with the benches; this privileged view at the bench expresses the building’s priorities far more than a uniform glass treatment would. Larger transparent areas are reserved for the atrium, where the glass expresses a tension with the existing building, provides views from multiple levels and vantage points in plan and section, and where users can choose where to occupy the space in response to interior conditions.
Gardens by the Bay is built for plants in addition to people. Like all greenhouses, its primary goal is to keep plants alive and growing by providing the right thermal and light conditions. Unlike most greenhouses, the goal of this particular project is to keep plants cooler than the outside conditions, rather than warmer. While Singapore’s climate is hot and humid, the plants on display are adapted to cool-dry and cool-moist environments, conditions which never occur naturally on the site. A further challenge is the client’s ambitious energy goal: the original mandate was for the Gardens to use no more energy than a ‘typical’ office building in Singapore, which is extremely difficult for all-glass cooled greenhouses. In fact, the project comes close to carbon neutrality.
Getting daylight into the greenhouses drives the entire design of the project, from skin to structure. Plants need an enormous amount of daylight to grow: for these species of plants to thrive, the project goal was to provide 45,000 lux for as many hours as possible. (By comparison, a typical office building needs around 300 lux for day-to-day tasks, which is 1/150th of the daylight needed in the greenhouses.) Because Singapore’s climate is often cloudy in the middle of the day, the greenhouses needed to be fully glazed to provide enough daylight. The greenhouses’ form allows daylight from all sides and the structure of the greenhouses was made as thin as possible to reduce shading the glass.
Cloud cover in Singapore
With this much unshaded glass, however, the greenhouses will heat up like traditional hothouses when the sky clears, contrary to the goal of providing cool interior environments with low energy use. Therefore the all-glass design needed to address solar gains without compromising daylight. The solution includes a series of elements, starting with the architectural volume and creating a layered skin. Both greenhouses are tall, large-volume spaces where warm air can rise to the top, in a zone without plants or people, and be exhausted. Between the structure and the skin the buildings include deployable shades, which can close to block direct sun and open during overcast times. The sailcloth shades unfurl from pockets within the main structural elements, and when closed they block most direct solar gains. Spectrally-selective glass further reduces solar heat gain while allowing visible light to pass through the glass. Beyond the skin, the buildings include innovative conditioning and energy systems such as displacement ventilation, chilled floors, desiccant dehumidification and trigeneneration powered by biomass, and other design elements that dramatically reduce the carbon footprint of the building.
Interaction of façade, shading, and mechanical systems
While the performance of all-glass buildings is often poor, Gardens by the Bay’s unusual program and location help it to avoid the typical problems. Due to Singapore’s warm climate, heat loss through the glass is not a concern and high levels of insulation were not needed. Visitors perceive themselves in specific biome and in a space that feels like the outdoors, so they have different expectations for visual and thermal comfort. Bright daylight and periodic glare are more easily tolerated, and visitors can move away from areas of direct sunlight if they choose.
While Gardens by the Bay includes all-glass buildings, its design arises from a series of local, specific conditions, including the needs of the plants and the local climate. The buildings’ volume and skin work together to transmit the aspects of local climate that are needed (daylight) and filter out what would be detrimental to the building’s program and performance (heat, humidity, solar gains). Gardens by the Bay’s architecture refers to traditional greenhouse icons while also embracing contemporary forms and means of production.
The idea of glass buildings has seduced architects since the modernist era, if not earlier. They hint at glittering, crystalline, layered forms; highly engineered and efficient structures; or at an invisible architecture. However our interest in these ideas has led to an architecture which is deployed everywhere with little cultural or climatic inflection. Critical Regionalism offers a reminder that creating a sense of place and responding to context is wholly compatible with great contemporary design. It leads us towards a more nuanced use of glass and transparency, and towards an architecture with greater meaning and smaller environmental impact.