Houston, the 550,000-square-foot mixed-use mega development, transforms a former United States Postal Service facility into a vibrant downtown mecca that combines concert venue, retail, dining, international market hall, and flexible co-working spaces. Atop this Texas complex sits a magical outdoor wonderland, SKYLAWN. Spanning 5 acres, the rooftop park and farm experience is a contemporary rustic-meets-urban greenspace designed by Hoerr Schaudt, with 360-degree, unobstructed views of the city’s skyline. The weaving rooftop layout includes a variety of glass skylights that vertically puncture the adaptive-reuse warehouse, bringing natural light in.
Working with Glass Flooring Systems, McLaren Engineering Group’s Facade + Envelope team provided the design, analysis, and structural engineering of the glass and glazing for a total of 40 walkable and decorative circular skylights and their connections to the structural steel. The group provided precise calculations taking into account various structural loads and rooftop wind conditions to perfect the innovative designs for the skylights of varying sizes and arrangements.
Three skylight configurations designated as walkable surfaces, range in size measuring 7 feet, 9 feet, and 10.5 feet in diameter. All of the walkable skylights feature a four ply 12mm-12mm-12mm-12mm laminate with 1.5mm SGP interlayers on the exterior side, a 19mm air gap, and a 6mm-6mm laminate with 1.5mm PVB interlayer on the interior side. All of the glass plies are fully tempered to provide the strongest possible system. The SGP Interlayer provides significant increases in stiffness and post-breakage strength which allows the glass to retain its shape in the event of failure, further protecting the pedestrians above. Additionally, the SGP interlayer provides a better clarity and transparency than the PVB interlayers, improving the quality of the visible light transmission into the space below. The exterior layer of the insulated glazing system is stepped past the interior layer and seal, and is supported by a custom built up framework, which ties into the base building framing below.
The other three skylight configurations are designated as non-walkable and measure the same ranges in size. Each of the three non-walkable configurations feature a unique glass makeup and are sloped up to 18.43 degrees.
The 7ft and 9ft systems have a makeup composed of a monolithic layer on the exterior side, a 19mm air gap, and a laminate with PVB interlayer on the interior side, while the 10.5 ft system utilizes a laminated exterior layer. Due to the slope of these systems and lower system weight, wind load suction was a larger design concern. As such, the support details were modified to provide a stronger resistance to uplift. The glass at the non-walkable systems does not stagger past the interior layer, and instead both layers are flush along the perimeter. This allows for a larger silicone seal which is structurally designed to prevent uplift from the larger wind gusts.
For each of these systems, both walkable and non-walkable, McLaren provided designs and analysis considering the in-service conditions of the glass as well as a safety model. These safety models assumed that some of the glass material has broken, and confirms that the system is able to retain its structural performance despite a sudden loss of section.