SINTERED STONE FACADE CASE STUDY

Photos courtesy of Neolith®

Project: AC Hotel and Residence Inn
Location: Dallas
Architect: 5G Studio Collaborative

The Project: This prominent Marriot-branded hotel sits at the center of a new $4.25-billion mixed-use development in bustling Dallas Midtown. Containing a significant number of buildings, people, and activity, this area has been dubbed a ‘city within a city.’ Dallas Midtown has seen a revitalization in recent years that is set to transform the urban landscape of this sprawling Texan metropolis.

The Challenge: Award-winning, Dallas-based architecture firm 5G Studio Collaborative was given the charge to provide an eye-catching and resilient exterior to this new hotel. The intent was to reflect the neighborhood’s resurgence and produce a key building that could contribute to it. At the same time, the national hotel chain required a look to match the timelessness, comfort, and authenticity of the Marriott brand.

The Design Solution: Considering all of the above, the architects sought an outside-of-the-box, contemporary design. Strong geometric shapes and deep three-dimensionality were used to achieve that end. A particular highlight is found along the hotel’s striking 5,000-square-foot entrance facade. The design at this critical focal point features thoughtfully designed trapezoid-shaped sintered stone slabs carefully put together by local fabricator, distributor, and installer Holland Marble. The design team found the sintered stone to be an ideal choice to meet the multiple demands being imposed on the makeup of the facade. Lauren Cadieux, associate and designer at 5G Studio Collaborative, comments, “The client requested a natural-looking material for this project; however, genuine rock such as marble is susceptible to staining and breakage. We suggested sintered stone because not only is it classic and elegant, but it is also strong and long-lasting.” Notably, the thin sintered stone panels are also much lighter in weight than full-thickness natural stone panels.

The Results: Cadieux comments, “The design journey was an enjoyable one, as we were able to maintain the initial concept right from the beginning stages until completion. We are very happy with the end result: a seemingly ‘floating’ facade that transitions effortlessly across the front, west, and east sides of the exterior and also has a welcoming effect—an aspect vital to a commercial space such as a hotel.”

Energy-Conserving Fenestration Systems

Fenestration usually figures prominently in most building facades. This can include windows, doors, louvres, vents, wall panels, skylights, storefronts, curtain walls, and sloped glazed systems. For any of these systems to be installed in a building facade, they need to have a manufactured frame to hold them in place and secure them to the rest of the building. In most commercial buildings, the material of choice is usually an aluminum frame or support system of various types. The reasons for its use are based on its lightweight but inherently strong nature as a material, its ability to avoid rust or corrosion, its rather economical workability, and the variety of colors and finishes in which it is available. However, it is also an excellent conductor of heat, which makes its use on building facades a concern when addressing energy-conserving design and compliance with energy codes, as the aluminum acts as a thermal bridge between inside and outside. This is true in both cold and warm climates as well as extreme weather conditions.

Manufacturers of aluminum framing systems for fenestration have been addressing the thermal issue for decades and continue to develop products that maintain their structural integrity while offering improved thermal performance. The key component is the addition of a thermal break or barrier in the aluminum frames, usually in line with the location of glass or other glazing in the frame. The intent is that the interior and exterior portions of the frame are separated with a structurally rigid but less thermally conductive material. The details of how that break is created and the choice of materials used are what tend to differentiate various products from each other.

Commonly, there are three choices of material used as thermal breaks or barrier material in commercial fenestration systems: vinyl plastic, polyamide nylon, and polyurethane polymer. Each has different thermal and structural properties, so finding the best choice is a combination of understanding these properties and the way they work with the details of a particular aluminum frame profile. This relationship is what manufacturers work on improving and perfecting to provide products that are reliable, economical, and functional.

Photo: © Paul Cosby Architectural Photography; Image: © Tubelite Inc.

The aluminum framing used in fenestration systems include tested and proven thermal breaks or barriers to improve thermal performance while maintaining structural integrity and overall performance.

Of late, polyurethane has received a good bit of attention as a thermal-barrier material in aluminum frames since it can provide superior thermal performance to other choices. For example, using standard test procedures based on the National Fenestration Rating Council (NFRC) 101, U-factors of frames with different thermal-barrier materials can be determined. In a comparison of thermal conductivity of materials according to ASTM C518 standard test method, polyamide 6.6 with 25 percent glass fiber showed a thermal conductivity of 2.08. By contrast, a vinyl barrier produced a better (i.e., lower) result at 1.18, while polyurethane performed the best at 0.84. The significance of the differences in performance, as it relates to the design of the aluminum frame, is that a lower-conducting material will not need as wide a gap to achieve a targeted thermal performance. For example, in at least one frame comparison, a polyamide thermal barrier was used to achieve a U-factor of 0.39 but required a 24-millimeter gap to do so. By contrast, a polyurethane barrier was used to also achieve a U-factor of 0.39 but only required a 15.8-millimeter gap. A smaller gap can mean better structural performance of the frame and possibly thinner overall profiles of products. Hence, achieving better thermal performance in thinner breaks has advantages when seeking to create better fenestration products that allow better sightlines, more structural integrity, and durability.

The most proven approach to effectively install the thermal-barrier material that isolates the inner and outer frames is referred to as a “pour and de-bridge” process. This is based on first creating an extruded aluminum profile that has been designed with a strategically placed channel in the middle of the frame piece. This channel is typically U-shaped and open to the top to receive the thermal-barrier material. Once ready, the thermal-barrier material is installed using specialized equipment designed for this purpose. If polyurethane is used, then it is literally poured in liquid form into the predesigned channel. Then, within minutes, polyurethane solidifies into a very strong structural polymer. The final step in the process cuts and removes the metal thermal bridge from the bottom of the channel to produce a true, non-metal-to-metal structural thermal barrier. This pour and de-bridge method is suitable for withstanding demanding climates and conditions with high-performance requirements in terms of impact resistance, shear strength, and heat distortion.

Remarking on the capabilities of such systems, Mary Avery, vice president of marketing at Tubelite, explains, “In colder climates, this type of system provides superior energy results and condensation resistance using multiple thermal barriers, while providing structural integrity and aesthetic flexibility.” She continues, “Optimizing thermal performance helps lower the load on HVAC systems and reduces associated energy costs, while maintaining a comfortable interior temperature.” She also notes that the reduction of condensation can improve a building’s appearance and minimize moisture damage to adjacent building materials.

FENESTRATION SYSTEM CASE STUDY

Photo: © Paul Cosby Architectural Photography

Project: Baker Center
Location: Minneapolis
Architect: RSP Architects
Certification: LEED v3 Silver – BD+C: Core and Shell

The Project: Located in downtown Minneapolis, which averages 53 inches of snowfall per year—double the average snowfall of the United States—the historic Baker Center offers more than a million square feet of mixed retail and office space. The historic structure is actually a composite of four Art Deco buildings.

The Challenge: Three of the center’s original buildings—the Baker Building, the Roanoke Building and the Investors Building—were built in the 1920s. The fourth piece of the complex—the 730 Building—was constructed in 1968. The challenge was pulling them all together with a single facade that would not only look sleek but also produce excellent thermal performance against the tough northern winters. Further complicating matters was the absence of original architectural drawings. There were also different construction techniques used during various retrofits and remodeling of each building over the past several decades.

The Design Solution: The Baker Center project team modernized the 93-year-old downtown icon while maintaining some of its history through design elements. “The goal of the Baker Center design was to honor the historic aspects of the buildings while creating unique modern spaces to support today’s mobile worker,” states David Serrano, AIA, a principal with RSP, the architectural firm heading up the design. “The result takes advantage of the Art Deco bones of the building while introducing forward-thinking amenities like the media wall in the lobby, a concierge desk, and a rooftop deck.”

In addressing the building exterior, the architects designed a new facade to both create a visually cohesive presence and address the needed energy performance. The main entrance at the corner of Eighth and Marquette streets showcases an exterior with a sleek glass lobby enclosed with a storefront system that is detailed and specified for energy performance. In particular, a pour and debridge thermal-barrier system was incorporated into a dual-pocket storefront system. The building’s dramatic corner design, from the fourth floor to the top floor, is comprised of a high-performance curtain wall system. Using structural aluminum fenestration materials with polyurethane polymer thermal barriers, along with solar control low-e glazing, helps to optimize energy performance in this commercial building, thus increasing comfort and lowering operational costs. The curtain wall and storefront framing used are ideal for both cold and warm conditions, providing high energy efficiency and condensation resistance.

The Results: “It was a logistically challenging project,” admits Scott Ide of Brin Contract Glazing. “Now that the project is completed, everybody is happy with it. It is a better-performing building with a dramatically improved look.”