Architectural Record BE - Building Enclosure

Emerging Building Envelope Solutions You Can Use Today

Innovative trends in building envelope design, construction and commissioning are helping teams deliver high-performance enclosures to meet challenging project requirements.
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Building Enclosure
By Daniel J. Overbey, AIA, NCARB, LEED AP (BD+C, ID+C, O+M), WELL AP

High-Performance Translucent Buildings Systems

On the topic of glazing assemblies, the next generation of high-performance translucent building systems offer a budget-friendly, elegant side-lighting solution. From single-story to mid-rise construction, these wall systems convert sunlight into glare-free ambient daylight with minimal heat exchange. Typically factory unitized, these systems are among the most highly insulated light transmitting fenestration solutions on the market.

The glazing units are filled with aerogel, a synthetic porous ultralight material derived from silica, and a liquid solvent such as ethanol. The aerogel is what gives the translucent panels their superior thermal performance versus typical insulated glass. In addition, translucent building systems are available with options for high-impact, hurricane rated walls and windows, a Class A fire rating and blast resistant construction. Modern advancements have also thwarted the infamous “yellowing” that tended to occur in past generations of the products as a result of prolonged exposure to ultraviolet solar radiation.

Structural Glass

An emerging marketplace for structural glass wall solutions is enabling designers to enhance structures with impressive, expansive areas of total vision. They function as a type of curtainwall system consisting of glass that is bonded or anchored back to a structure without continuously gasketed aluminum pressure plates/caps. The glazing units can be comprised of virtually any type of glass—including insulated glass units. The backup framing system may be aluminum mullions similar to a traditional curtainwall system. However, contemporary product offerings may consist of glass mullions, steel blades, stainless steel spider fittings, cables or stainless steel rods. The system may use extruded silicone/ethylene propylene diene monomer (EPDM) gaskets or a wet-sealed silicone.

There are many aesthetic virtues of a structural glass system including a nearly seamless, continuous glass look with less visual interruptions across a façade. They can resist wind and snow loads. Some systems can resist seismic forces. There are notable relative energy performance attributes as well. Traditional curtainwall systems can conduct large amount of heat transfer through the metal framing. With little to no exposed exterior metal, structural glass exhibits less thermal bridging.

Green Roofs and Walls

In response to an increasing desire to add green spaces and visual connections to nature within the built environment, verdant surfaces—i.e., green roofs and walls—have been growing in popularity. Today, the marketplace provides a diverse array of options to suit a wide range of project types. Incorporating vegetation into building envelope solutions offers a unique dimension of texture, symbolism and seasonal dynamism to a structure.

Green Roofs

In the most simplistic of terms, green roofs can be defined as planting beds installed atop a building’s roof structure. Amidst a spectrum of variations, green roof systems are typically defined by three classifications: extensive, intensive and semi-intensive.

Extensive green roofs are the shallowest of the three classifications. With an overall depth between 3–5 inches, the fully saturated weight of this system will typically vary between 15–25 pounds/square-foot. Extensive green roofs will typically exhibit hardy species of mosses, sedums, succulents, herbs and some types of grasses. This classification of green roof may not require permanent irrigation and is relatively low-cost and lowmaintenance. However, the potential for rainwater sequestration is minimal and it is not capable of harboring a diverse array of plant species.

Intensive green roofs are on the other end of the spectrum. This classification of green roof will range from 7-over 24 inches in depth, correlating with a saturated weight of 35-over 80 pounds/square-foot. Dependent on the system depth and irrigation, intensive green roofs can support the widest range of plants including perennials, turf grass, putting green, vegetable gardens, shrubs and many species of trees. Intensive green roofs require permanent irrigation systems and can contribute meaningfully to rainwater sequestration.

Semi-intensive green roofs constitute the middle ground between the extensive and intensive classifications. Typical depths range from 5–7 inches. The saturated weight will usually vary between 25-over 40 pounds/square-foot. Some irrigation may be necessary as semi-intensive green roofs are capable of supporting perennials and shrubs in addition to the succulents and other small plants supported by less intensive green roofs systems.

Green roofs may be built-up atop a building’s roof structure or modular tray systems can be installed atop a slip sheet over a low-sloped membrane roof system.

In response to unique requirements on a number of green roof installations, the industry has introduced several innovative systems components to the market. Some installs offer unique clip systems that fasten to draped stainless steel mesh to hold growing media along a sloped roof. In order to address concerns about leak detection, a manufacturer has developed a low-voltage test method that creates an electrical potential difference between a non-conductive membrane surface and the conductive structural deck or substrate, which is earthed or grounded as part of the green roof system. The result is a non-destructive method of waterproofing verification and pin-point leak detection.

Picture of green roof atop the California Academy of Sciences in San Francisco, Calif.

Photo courtesy of author

An undulating extensive green roof atop the California Academy of Sciences in San Francisco, Calif.

Green Walls

Exterior green wall systems can be defined by two basic classifications: living screens and living walls.

Living screens refer to the broad category of green wall systems that consist of climbing vines and ivy on walls, cables, scaffolding, modular mesh systems and so on. While the concept of plants growing up a façade is not new, research has shown that over time many species of plants can damage wall cladding, which presents long-term durability concerns. In response, some manufacturers now offer products specifically designed to foster plant growth while keeping the vegetation off of the wall itself.

Living walls are defined by the dense, vertical gardens that are harbored by a modular systems affixed to the building structure. Some living wall systems may grow plants hydroponically within a water-soaked mesh fabric, while other systems may employ lightweight soils (similar to the growing media used for green roofs) in fabric pockets or trays.

Most green wall systems require permanent irrigation and project teams should coordinate with installers to ensure that methods are identified to ensure the delivery of nutrients and fertilizers as necessary. Living walls are more robust than living screens and thus have the potential to provide a far more diverse pallet of flora. However, living walls also require more maintenance.

Picture of the outdoor living wall system at Pulliam Square in Indianapolis, Ind.

Photo courtesy of Barth Hendrickson and Browning Day Mullins Dierdorf

Picture of the outdoor living wall system at Pulliam Square in Indianapolis, Ind.

Photo courtesy of Douglas Adams and Browning Day Mullins Dierdorf

Pulliam Square in Indianapolis, Ind., features an outdoor living wall system.

All-in-One Systems

Design and construction teams have witnessed the rise of an increasingly complicated field of construction specifications. For any given project, there is a high likelihood that the contract documents contain technically incompatible specifications. Most of the time these issues can be identified and worked through in the field. However, if undetected, they can make components of a building envelope assembly susceptible to failure, leading to damages, voided warranties and claims.

In order to take away the guesswork and foster consistent, compatible project specifications, multiple industry leaders in different trades have aligned in order to offer complete (i.e., all-in-one) wall systems. In essence, the notion is to have one assembly solution from a single supplier with a single-source warranty.

These all-in-one assemblies have been engineered to bring together sophisticated, category-leading components that are completely compatible, code compliant and warrantied to work together to deliver outstanding performance—and bring high-performance building envelope solutions to the next level for architects and contractors. They come with comprehensive details and quality assurance programs. Today, there are systems for wood studs, metal studs and concrete masonry unit (CMU) wall assemblies.

 

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Originally published in Building Enclosure

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