September 11, 2020
By Jim Leslie and Kevin Smith
There are at least 22 windy days per year on average in Regina, Calgary, Hamilton, Toronto, Winnipeg, and Moncton. Of these, Regina has the most at 29 days and the highest speeds at 18 km/h (11 mph) on average. Across the country, buildings and structures can apply this abundant natural resource. Wind-driven kinetic façade systems’ flapper-panel designs respond to air currents, adding dynamic movement to create the look of rolling waves across the wall system. Suitable for both small- and large-scale projects, popular applications include transit and parking facilities, cultural institutions, entertainment venues, and artistic installations.
A kinetic structure effectively alters the environment around its installation and, in turn, the structure is also affected by its surrounding conditions. The façade system, therefore, will need to possess specific design measures to ensure the building structure, as well as the occupants, are in harmony with the existing enclosing environment.
Design and specification considerations
With a kinetic façade system, the focus is on material selection; the flapper elements’ size, shape, and spacing; and the suspension systems that support them. Integration of lighting elements can also play a key role in the system’s design and the project’s final appearance.
As with any façade, material selection and arrangement are critical to long-term performance of the system. Due to the dynamic nature of a kinetic façade, it is critical to incorporate movement and, therefore, to consider wear and proper selection of proven ultraviolet (UV)- and abrasion-resistant materials. This often involves customized, accelerated testing of components and assemblies. It is important to note, the parts contributing to the façade system’s motion must be UV-resistant to ensure long-term performance. For instance, the bushings in a rod-mount suspension system should be friction-free, long-lasting and hold up to years of UV exposure. If they became brittle and cracked, the flapper would no longer move properly. This could result in metal on metal grinding.
Physical mockups are also critically important during the developmental phases to assist the design team, building owner, and sometimes, the jurisdictional authority in understanding the visual and auditory effects of the proposed façade.
Flapper and lighting elements
Wind-driven, dynamic façade systems support a wide variety of flapper shapes, sizes, and materials. While aluminum is the most popular, other options include perforated materials, stainless steel, polycarbonate, polytetrafluoroethylene (PTFE), acrylic, and even polyvinylidene fluoride (PVDF) films.
A wide variety of flapper finishes also are available. Standard finishes include anodized aluminum or fluoropolymer paint. Higher gloss finishes, such as metallic coatings, tend to accentuate the visual kinetic action of the façade. Colour-shifting and textured finishes also produce interesting visual effects.
Patterns also can be printed or perforated on flapper elements. This can range from basic screen printing of simple patterns to full-colour image printing. Large images can be segmented or pixelated across the entire kinetic façade to bring a dynamic appearance to an artistic or branded image.
Flapper elements fabricated from translucent materials allow natural light to pass through the façade. Translucent acrylic and polycarbonate materials can be specified with infrared-blocking coatings to help manage unwanted solar heat gain inside the building.
Anti-reflective coatings on polycarbonate materials can reduce glare during the day, and at night could act as a backdrop for projected images and lighting effects. Regardless of the flapper element’s material composition, many kinetic façade installations incorporate illumination during the evening. Face lighting from above can be used to emulate a daytime view, while dramatic effects can be achieved through the use of various night lighting including backlighting, uplighting, or wall wash lighting.
To accommodate the specified flapper elements, there are three typical suspension systems to consider for wind-driven kinetic façade designs:
Each configuration possesses different performance and esthetic characteristics and baseline costs. Modified and custom systems also can be developed for unique project requirements.
For ease of delivery and installation, each of these suspension systems is typically factory-unitized. Dimensions commonly range from 1 x 1.2 m (3 x 4 ft) to 1.5 x 3.7 m (5 x 12 ft) in vertical or horizontal orientations.
For optimal cost and performance value, the drop-in suspension system is recommended. In this configuration, T-shaped kinetic flappers are easily inserted into a specially designed ‘rung’ extrusion system, significantly reducing the amount of time and labour required for fabrication.
The pin-mount suspension system allows the flapper elements to seemingly float in front of the support rungs and side rails as a veil. This configuration minimizes the appearance of the supporting structure. The pin-mount system allows for mixing flapper shapes to create geometric patterns and for installation at various mounting points, facilitating changes in kinetic activity.
Drop-in and pin-mount suspension systems allow the flappers to be removed and replaced without any specialized tools if repair or maintenance is needed. Both systems also accommodate up to a 90-degree range of motion.
Offering a 360-degree range of motion for the individual flappers, the rod-mount suspension system allows for greater intermittent views through the kinetic façade and minimizes the appearance of the horizontal supporting structure from within the building. They can also permit increased airflow and promote passive cooling. The vertical side rails are typically more prominent within the façade and the flappers can be replaced with simple tools.
Some manufacturers also offer cable-mount suspension systems. These systems suspend the kinetic elements or flappers between a combination of horizontal and/or vertical cables. The flapper replacement for cable-mount systems can involve costly and time-consuming restringing or replacement of the entire cable section.
Performance requirements are important on every building, and deserve extra attention with kinetic façade systems. Careful analysis is needed regarding the interaction between the kinetic façade elements and the building structure to which it is attached, as well as the impact of the structural behaviour on the design and cost of the system.
Structural loads, especially those due to positive and negative wind pressures, need to be assessed to ensure the façade system meets the required strength specifications and the esthetic requirements. Other loads that are influential in the specification, design, and installation of the kinetic façade include ice and snow loads and seismic loads.
The method of attaching the façade elements to the building also needs to be examined and coordinated as early as possible during the design and specification phase. For example, will the kinetic panels be self-supporting, or will secondary supports need to be installed? In concrete structures, this means evaluating their embeds and anchors, their interaction with existing reinforcement configurations, and their required supporting system.
The kinetic façade system also needs to be compatible with anticipated building movements. The attachment design should account for the dynamic deflections of various types of buildings and structural systems. In parking structures, for example, the dynamic deflections from vehicle traffic must be adequately taken into account. Kinetic façade systems that cannot accommodate the required deflections run the risk of failure. It is, therefore, crucial that mounting systems are designed for these deflections to ensure long-term integrity of the system is maintained. Close co-ordination between the façade designer and manufacturer, and the engineer of record for the supporting building structure is critical even in the early phases of the design process.
A building’s structural demands may also govern the testing requirements of the kinetic façade, such as ASTM E-330/E-330M, Structural Performance of Exterior Windows, Doors, Skylights and Curtain Walls by Uniform Static Air Pressure Difference, which is referenced in the 2015 National Building Code of Canada (NBC). These testing requirements are often driven by local codes, however, the desired façade performance may be the determining factor.
A project’s design and specification phase is the best time to critically analyze esthetic and performance requirements, and to make adjustments to ensure its success. Once the project moves into fabrication and installation, corrections become more costly.
Budgeting for a kinetic façade system usually entails striking a balance between the desired esthetic and performance goals of the project. Since kinetic façade systems are delivered to a jobsite in pre-assembled units, most installations range from $9 to $15 per 1 m2 (10 sf), depending on several factors plus labour costs.
Additional costs also may be incurred as a result of testing requirements of the location or application. Local labour costs, union requirements, site access, street closures, timing and scheduling, and project duration, are just some of the installation-related factors that can affect the final cost of kinetic façade systems.
In addition to the costs associated with installation, system type, and testing, other relatively small hardware or structural changes can have a profound impact on the final cost. These include the following.
Flapper density is defined as the number of flappers per square metre. The smaller the flappers, the more individual handling, assembly, labour, and mounting parts are required. For example, it would take about four 130 x 130-mm (5 x 5-in.) flappers to fill a 1-m2 area, assuming a 25-mm (1-in.) space between flappers, while it would take nine 76 x 76 mm (3 x 3 in.) flappers to fill the same area. This increased number of flappers translates to more than double the amount of assembly time, labour, mounting hardware, etc.
Flapper elements produced from pre-finished sheet material, such as anodized or painted aluminum, are typically more cost-effective than post-finished flappers. The type of finish also influences the overall cost of the kinetic façade. For example, standard anodize and painted colours will be more economically priced than exotic colours and multi-step coatings. The cost and benefits of each type of finish should be analyzed to ensure the flapper finish does not adversely affect the project budget.
Finish on back of flappers
Finishing the back-side of flappers can incur additional costs because it requires the use of extra material and resources. Anodized flappers will have both front and back faces coated with the same process. Painted flappers, on the other hand, can accommodate different coatings on the front and back face. While both sides can be coated with the same finish, opting for a wash coating on the rear face may reduce overall cost. This painting method is acceptable on the back side of the flapper when it is either not visible or barely visible, which will be the majority of applications.
Supporting structure finish
In addition to the finish on flapper elements, the finish applied to the supporting structure (i.e. the horizontal and vertical mounting rails), also influences the cost of the total façade system. A darker, low-sheen finish is typically applied to the supporting elements to accentuate the esthetic quality of the flapper elements. These framing members are usually painted.
Building spans and loads
The required span and environmental loads can affect the weight and size of the kinetic façade’s structural elements. This can, in turn, impact the cost of the system.
The mounting hardware and anchoring systems of the flapper elements depend heavily on the required span, deflections, and building substrate materials. This hardware can consist of embeds integrated into the building structure or post-applied anchors supplied by the façade system manufacturer.
Manufacturer and installer considerations
Given the complexity of kinetic façade systems, seek an experienced designer and manufacturer to participate early in the project’s design and specification. Look for one offering preliminary cost estimating, mockups, and a variety of fabrication and installation options to meet each project’s functional and esthetic requirements. Some manufacturers will also manage all aspects of the installation process, providing a single-source price directly to the building owner or general contractor.
For maximum cost efficiency, a kinetic façade manufacturer may be willing to deliver its services solely as a material supplier. With this solution, materials are provided directly to a local installation contractor already involved with the project, such as a glazier, curtain wall installer, roofer, or general contractor. Startup supervision and initial training for installation crews may be included as part of these services. Although training/certification is typically not required by kinetic façade manufacturers, the author, however, strongly recommends that installers work closely with manufacturers to ensure proper installation.
In this role as material supplier, the façade system manufacturer may also offer pre-bid support. Generally, this involves formally presenting the system, its installation processes, and other relevant documentation to prospective general contractors and/or installers. Regardless of the procurement process, formally presenting the product ensures prospective bidders have a thorough knowledge of the system, eventually resulting in better quality and more informed bids.
Once the bid is approved and the contract awarded, a successful installation of a kinetic façade is measured in terms of time, cost, and quality. It requires the synergistic co-ordination of various activities including design, engineering, testing, fabrication, delivery, and installation. This begins during the conceptual design phase, with the development of the project schedule.
Typical project durations range from 12 to 20 weeks from the time of award. The type of overall design, the complexity of the kinetic elements, and the scope of the installation are some of the factors that can affect this timeframe. For large-scale kinetic façade systems, delivery schedules are often phased at various construction stages to allow a continuous stream of material through the duration of the installation. This phased method of delivery avoids potential damage to components stored onsite and helps conserve space by limiting site laydown and storage areas.
The kinetic façade installation is typically arranged as one of the final undertakings during building construction, thus limiting the exposure of the façade elements to potentially damaging activities from adjacent trades.
When considering a kinetic façade installation, several site-related factors must be taken into account to ensure the chosen system functions as intended. The geographical location of the building is one of the most crucial aspects of successful kinetic façade design, specification, and installation.
Some location-specific questions that need to be considered during the conceptual design stages are:
Also essential is the building’s orientation—the position of the structure relative to the surrounding environment. How the orientation affects airflow, façade visibility, as well as the fall of direct and indirect light at various times of the day, should be assessed to ensure maximum façade performance.
Following an analysis of the building’s orientation, the viewing perspectives of the kinetic façade need to be considered. In other words, at what vantage points and viewing distances can the façade be observed for maximum visual impact? For instance, in tight urban environments, where most vantage points are nearfield, smaller flapper elements should be considered to achieve a denser, less pixelated appearance. Conversely, for installations where the façade will likely be viewed at greater distances, larger flapper sizes can be used to achieve the same visual impact at a lower cost. Additionally, if the kinetic façade serves as a shading device, the esthetic appearance of the system from within the building may also need to be taken into account.
The solar angle, and its effect on selected materials and associated glare, is another factor in the design, specification, and installation of kinetic façades. The angles at which the sunlight strikes the façade’s elements can have a profound impact on the esthetic. For specific environments, such as those near airports or in tight urban settings, glare resulting from the selection of highly reflective materials may be undesirable. In other cases, where indirect light is predominant, a material with more reflectance can accentuate the façade’s kinetic activity.
Finally, while the physical properties of the façade’s elements and its interaction with the surrounding environment are critical, property/setback limitations, as well as zoning/code considerations, also need to be assessed during façade selection and installation. With respect to setback limitations, the appropriate cadastral map and other relevant property documentation should be consulted to ensure the flappers have enough clearance to exhibit a full range of motion without violating any setback requirements.
Additionally, all local zoning ordinances should be researched thoroughly to determine what, if any, regulations apply. For instance, some municipalities may require façade installations to comply with sign ordinances, especially where lettering or designs are applied or expressed through the arrangement of coloured flappers. Other jurisdictions may have restrictions on moving elements. In applications where the kinetic façade panels also serve as guardrails, they must be designed, specified, and installed in accordance with the relevant safety standards and specifications. For buildings, such as garage structures, where codes and standards specify free air ventilation requirements, the façade panels and elements should be sized to meet these specifications.
All kinetic installations can produce some level of ambient sound under higher wind conditions, therefore, the chosen system should be one that does not generate sound considered to be excessive for the given environment. The suspension system, construction material, and flapper geometry can be adjusted to ensure the level, tone, and timbre of the resulting sound is acceptable. Many manufacturers engineer systems with spacers between the flappers to reduce the collateral noise. It is, however, crucial that the volume and quality of sound generated by the installation are considered as early as possible in the design and specification process, and are verified with full-scale mockups.
Like almost any reachable element of a building, a façade is vulnerable to vandalism. The accessibility of the façade and the nature of the installation area should be assessed to determine the susceptibility of its elements to such issues. Ground-level elements should be given particular attention, especially if they are within reach of pedestrians. In parking structures and other applications where façade elements are easily accessible, it may be worthwhile to install protective mesh on the rear of unitized sections to prevent malicious vandalism, or to apply anti-graffiti coatings on the flapper elements. In any case, the ease of flapper replacement should be considered in case damage may occur.
Proper kinetic façade design should discourage bird or insect nesting. Minimized fixed horizontal surfaces, no open hollow voids, clear openings between moving elements, appropriate suspension systems, and reflective materials, are just some of the measures that can be employed to deter
With the installation complete, minimal manual cleaning is required; naturally occurring rainfall is typically sufficient. In situations where more advanced cleaning is desired, mild pressure washing can be employed. While there are no routine maintenance requirements for most kinetic façade systems, periodic inspections for issues, such as storm damage or vandalism, as well as mounting connection checks are highly recommended.
While every challenge of site location, orientation, and environmental surroundings cannot be predicted, addressing the above considerations will set a kinetic façade project on the path to success.
With early involvement and ongoing collaboration between the designer, specifier, installer, and manufacturer, wind-driven kinetic façade systems add a dynamic and distinctive element to parking garages, retail centres, museums, sports arenas, theatres, and other building structures.
Jim Leslie is the general manager of EXTECH/Exterior Technologies, Inc., in Pittsburgh, Pa., leading the company’s mission to improve lives through innovation in daylighting systems, natural ventilation, and other building envelope systems. Working closely with architects and specifiers, Leslie and his team redefine the intersection between the natural and built environments with wall, window, skylight, canopy, and custom systems, such as dynamic façade designs. Leslie has a bachelor of science in mathematics from Penn State University and is a member of the American Production and Inventory Control Society (APICS). He can be reached at email@example.com.
Kevin Smith is a registered architect, and leads EXTECH’s team of architects and engineers as director of product application and development. He brings more than three decades of experience in designing commercial, civil, industrial, and transportation projects, as well as daylighting, static, and kinetic façades. He earned a bachelor of architecture from Carnegie Mellon University. He can be reached
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