The facade of the building has always been a significant element for architectural design, and not only for the purposes of shielding the interior from the weather. Yet, within the context of the high-density development, its role acquires a significantly more complex set of demands – to choreograph the flow of pedestrians, to act as the corporate image interface, to frame the view from the street, to perform as an ultra-efficient energy converter – and those are only the main ones. At the same time, it appears that the redefinition of the building frontage is not just another architectural move but a design revolution in its own right.
Approximately 68% of the world’s population will be living in urban areas by 2050, up from 55% in 2018 (UN DESA, World Urbanization Prospects). The buildings accommodating this population boom are not embedded in isolated sites, but rather rise within the urban tissue, where the view from the street, the spatial relations between the built forms, the micro-zoning regulations, and the thermal performances interact with a degree of complexity unavailable in scattered developments.
First impressions do not come from a distance
While the perspective view from afar is generally appreciated in architectural practice, the pedestrian’s eye needs a closer look to engage with the building. In a high-density environment, it is common to experience the first building impression within 5-15 meters of the facade. At this distance, the architectural legibility takes on a completely different meaning.
For instance, the large-scale glass monoliths and aluminum curtain walls typical for the high-rise development appear as uniform surfaces from afar but transform into a dull and bare surface at closer distance. At 10 meters, human eye perceives detail, pattern, texture, and depth – the absence of which makes surfaces generic and difficult to engage with. Not only does the generic building appearance fail to trigger an emotional response, but it also tends to blend with its neighbors since there are few architectural differentiators at this scale besides the building’s profile.
This is why the ground portion of any development, and the podium in particular, plays a disproportionately critical role in the formation of architectural legibility. While the top portion of the building often features a uniform business or residential module repeating throughout the entire height, the base is the only differentiating element on the facade. It is the element of first engagement for the building visitor, and it is therefore critical for establishing a positive first impression. Not only does it serve as the brand discoverability element by virtue of its unique architecture, but it also guides the pedestrian flow. And this is why the choice of materials for the building’s base, its patterns, details, and articulation, is of paramount importance to the design of a high-density building.
Creating wayfinding opportunities presents an opportunity to stand out
Within the high-density urban fabric, commercial buildings present a problem of similarity – similar height, similar floor plans, similar materials – and, as such, have little architectural language to communicate their unique identity. They essentially become indistinct from each other aside from the brand’s nameplate on the lobby wall. This creates a degree of disorientation among pedestrians attempting to navigate the district, with unavoidable delays ensuing at each building entrance due to the uncertainty of one’s location.
The building façade can be leveraged to create unique visual tags easily identifiable by pedestrians at a distance. It is critical to recognize that the language of materials, colors, patterns, and detail elements used within the building’s architectural surface can serve to establish its identity within the larger commercial complex. A subtle change in color, material, panel size, pattern, or texture can be employed to create a unique tag for the building in question. A terracotta screen on the first two floors, a change in metal tone on the third, a subtle pattern variation on the fourth – elements such as these allow the pedestrian to recognize the building at a distance and orient themselves within the urban environment without effort.
This is wayfinding at the building scale, and it should be considered within the design priorities for commercial projects. Creating unique visual tags for each building in a development is, in fact, a critical step in its architectural legibility strategy. The value of such a strategy can be easily underestimated owing to its simplicity of execution, but it is of paramount importance to the functionality of the pedestrian environment. The test of such a project’s success can be found in whether the building can be identified by a visitor from a distance on a cloudy day without having had the opportunity to read its nameplate.
The facade is the brand’s most valuable asset
As the commercial building type matures, so does its design language. Contemporary commercial buildings across the world adopt similar floor plans, open-plan offices, exposed services, and standard height ceilings. At best, the lobbies of two similar buildings can be differentiated by their interior design, but one would have to enter both to make the distinction. Essentially, aside from the location and nameplate, commercial buildings offer little to the visitor seeking to identify the place they are entering. This is why the architectural surface of the building, and the language it communicates to the passer-by, is of such importance to the commercial building type.
This represents a paradigm shift of sorts, as the facade design in contemporary commercial building projects tends to be led by strategic, brand-driven considerations rather than the conventional management practice of balancing performance and budget. For the large-scale commercial developer, the architectural surface of the building presents an investment opportunity in and of itself. The language of material, pattern, light, shadow, texture, and detail encoded into it will resurface in the marketing and eventually become recognizable by the visitor long after the initial fifteen-year lease expiration.
This is the context within which the commercial building cladding decisions must be considered: as the strategic brand investment rather than the tactical fit-out detail. This is especially true for the commercial building projects competing within the larger urban environment to attract the same pool of tenants and visitors. For such developments, the value of their exterior presentation is functionally equivalent to the value of the interior fit-out selected to accommodate the short-term lease commitments.
Energy performance makes its appearance on the facade
Once the image and wayfinding roles of the building facade are secured, the question of its thermal performance can be addressed. For the high-rise commercial building type in particular, the building envelope is often the most energy-critical element of the development, and its design decisions can have a critical impact on the overall performance of the building. Essentially, it is the envelope which defines the mechanical needs of the development.
Within the commercial high-rise, it is the percentage of glazed areas within the building division that define the extent to which solar energy will penetrate the interior spaces. And the higher this percentage is, the greater will be the need for mechanical cooling within the building. With the performance needs of the core and the floor plates defined by the size, height, and orientation of the building, the choice of the glazing percentage within the division becomes purely strategic. At over 40-60 percent, the cooling needs of most buildings start to skyrocket, owing to the inability of the mechanical systems to offset the solar gain efficiently. This creates a dilemma of either compromising the views and daylight needs of the occupants or further expanding the mechanical needs and the mechanical footprint of the building.
The resolution of this dilemma lies in balancing the solar needs of the building division by incorporating additional areas of high-performance insulated cladding panels within the division. By selecting panel solutions with a sufficiently high thermal resistance, the solar gain of the glazed divisions can be offset, thus removing the pressure on the mechanical systems to perform beyond its means. At this point, the energy considerations of the building become interwoven with the image and wayfinding considerations, with the latter shaping how the former are presented as part of the building’s performance credentials. The choice and specification of cladding materials and systems therefore become significantly more involved, as multiple performance criteria (thermal transmittance, solar heat transmittance), as well as the balance between glazed and non-glazed divisions need to be considered.
LEED, Green Star, and WELL rating systems recognize this complexity and respond to it with specific performance criteria, which allow the project team to secure strategic value with respect to the performance of their building envelopes.
Materials and the ecology of the site
The building enclosure, then, performs a critical role in the ecology of the site. Its ability to repel or retain heat has a direct impact on the comfort of the pedestrians, workers, and visitors of the development. As the urban heat island effect begins to take hold in many metropolitan centers, the ability of the cladding system to reject heat rather than retain it will become a critical differentiator for the development in question. This is especially true for the high-rise commercial buildings, which are both contributors to the heat retention as well as victims of it.
It is therefore critical to select materials for the building enclosure based on their solar reflectance properties, which allow the surface to reject a substantial portion of solar energy rather than absorbing it. This is a critical enabler for the creation of the high-performance building districts, where the ecology of the development is optimized for the comfort of its occupants, and the performance of individual buildings is maximized within the constraints of the larger development. It is especially critical for the commercial building type, which typically accommodates the largest number of occupants within a given site.
However, the choice of the material with a high solar reflectance value becomes complicated by the increased potential for glare, and the challenges it introduces for the building’s occupants. Excessive glare from the reflecting surfaces of the building enclosure can interfere with the operation of the neighboring buildings, both by creating potentially unsafe conditions for the pedestrians below and by disrupting the operations of the building’s day-lit interiors.
This is why the choice of the reflective value for the building enclosure must be made within the context of a larger assessment of its impact on the urban environment. Ideally, the choice of the material and its solar reflectance value must be equal to the needs of the development and its ecology, as well as the potential impact on the neighboring buildings. In practice, the choice of a matte metal panel or fiber cement sidings over a high-gloss metallic aluminum finish tends to be dictated by the desire to avoid excessive glare and disruptions for the building’s day-lit interiors. Meanwhile, the selection of high-performance fiber cement or terracotta paneling tends to present a superior value proposition in terms of maintenance, as compared to the high-gloss finishes often associated with excessive solar gain and correspondingly increased cooling costs.
Code compliance defines building form
There is an interesting design sequencing conflict within many commercial building projects, stemming from the tendency to prioritize material selection over code compliance. In the design of high-density commercial developments, however, it is the regulatory framework which often defines the form of the building.
The massing of many high-rise commercial buildings is dictated at a detail level by the regulatory framework within which it must operate. Zoning codes, solar access planes, building setbacks, street wall height, and heritage overlays define the parameters of the development before any consideration of materials can be entertained. View corridors imposed by the local planning authority can add additional constraints, which must be responded to with equal design precision.
Within this context, the architectural surface of the development is defined by the massing, and the massing, in turn, is defined by the regulatory framework. And the constraints of the regulatory framework are seldom negotiable at the time of project inception. This creates a serious design conflict, as the design team must work within the limitations set out by the regulatory framework from the outset, rather than responding to its opportunities.
It is this design sequencing issue which places commercial developments within a high-density urban framework at a particular disadvantage, as compared to developments in less intensively developed areas. Within the code-compliance driven design sequencing framework, many commercial building projects become defined by their response to the regulatory framework. This response, in turn, becomes a design liability rather than an enabler, consuming significant design resources with no corresponding rewards for design excellence.
It is interesting to note, however, that many high-rise commercial developments in the high-density environment actually become enhanced by their adherence to the regulatory framework. This phenomenon is particularly noticeable at the level of the building articulation. The need to respond to the specific regulatory constraints often creates opportunities for enhanced pedestrian comfort, image, and performance at particular levels of the building. The recessed entry defining the pedestrian shelter, the articulation of the street wall, and the recessed portion at the level of the building setback can all be enhanced to capitalize on the opportunities created by the response to the regulatory framework.
The unitized method dominates due to logistics
High-density developments are characterized by limited construction rights and often by the shared use of the surrounding infrastructure. At the same time, they tend to be located in the center of large urban developments, which further complicate the logistics of large-scale commercial building developments. The combination of these forces tends to make the construction costs of such developments particularly sensitive to the choice of the building enclosure.
It is the unitized method which tends to dominate as the preferred method of curtain wall installation within the high-density development, due to the advantages it offers in terms of installation logistics. The construction logistics of the project are optimized, due to the ability to install the panels of the building enclosure within a reduced timeframe and with reduced impact on the traffic of the local infrastructure. Time, one of the most critical constraints of any construction project, is managed more efficiently, and the overall efficiency, as well as the quality of the work performed, is enhanced. And while the overall program timeline is reduced, the uniformity of the installation across the building facade allows many construction projects to accelerate their pace, installing the enclosure components on the upper level even before the lower level has been completed.
The value of the unitized method as the preferred mode of curtain wall installation within the context of the high-density development is therefore difficult to overestimate. The critical design sequencing issues it raises within the commercial building projects are largely resolved by the opportunities offered by the current building enclosure marketplace. The image and performance expectations of the building enclosure are no longer compromised by the selection of the unitized method, which itself is driven by the need to minimize the impact of construction within the high-density environment. At the same time, the opportunities of the unitized method are expanded, incorporating a variety of metal panel, fiber cement, terracotta, composite cladding solutions, glazing, and other finishes.
Maintainability is frequently a deal-breaker
The ecology of the high-density urban environment affects the maintenance and upkeep of the building enclosure in ways seldom experienced in low-density developments. The pollution, tailpipe emissions, construction dust, or other local phenomena can combine with the materials and finishes of the building enclosure to produce particularly difficult to clean deposits that affect the appearance of the development in a negative way. This compromises the intended performance of the enclosure, as well as the image and value of the development, and can become particularly difficult to address if the material choice does not account for the specific regional conditions.
It is critical that the choice of the material and finish account for both the regional conditions and the maintenance infrastructure necessary to preserve the building enclosure’s performance. Finishes that are particularly challenging to clean, and which therefore require specialized equipment or particular maintenance practices to address the regional ecology of the location should be avoided, as should finishes unavailable to the local contractor at the time of repairs. Such materials often need to be replaced, presenting additional costs and loss of value to the owner, as well as additional complications to the maintenance schedule. This, once again, illustrates the importance of considering the long-term performance and lifecycle costs of the material within the context of the local environment.
The building enclosure is an urban system
The building enclosure of a commercial development within the high-density environment stops being just a design statement. Within the high-rise building type, it mediates between the energy performance of the development and the micro-climate peculiar to the urban environment. It enhances the legibility of the development and therefore assists in the mediation of the pedestrian flow. It serves as the brand differentiator, and it is the element that makes the development memorable long after the initial discovery. Its properties and characteristics, in other words, directly impact the performance and image of the commercial development.
