High-Performance Building Envelope
Triple Glazing and Bird-Safe Glass
Stony Brook University, Institute for Engineering-Driven Medicine
Stony Brook, New York
Designed to be Net Zero Carbon Ready, this project will achieve the goal, in part, by optimizing the insulative properties of the building envelope. Doing so decreases the operational energy requirements of the building and thus, its carbon footprint.
While the overall opaque wall-to-window ratio is 4:1 – a very sustainable ratio – typical double-paned Insulated Glass Units (IGU) in curtain wall systems would not be insulative enough for the requirements of this building. Therefore, the building employs triple-paned IGUs with an SHGC of 0.25 and U-value of 0.13. This U-value is the equivalent of an R7.7 wall, rather than the R2.9 typical for double-paned IGUs. The higher insulative value reduces both the heating and cooling load on the HVAC systems and furthermore, eliminates the need supplemental baseboard radiation throughout the building. (The increased first cost of the glazing system is essentially offset by the savings gleaned from not needing to install the baseboard heating system.)
Beyond the triple glazing itself, 60% custom digital frit pattern will be applied to the east and west glazed facades. The pattern will reduce both glare as well as morning and afternoon solar heat gain, thus reducing the cooling load and consequently the operational energy required by the building. Again, lowering operational reduces carbon footprint.
Separate from energy and carbon savings, the custom frit pattern on the east and west glazing in conjunction with a special gray dot pattern frit on south façade will also serve an important bird-welfare purpose. Every year in the U.S. and Canada, it is estimated that as many as 600 million birds die in collisions with building glass. Because this building is located in a wooded location, bird flight paths are known to cross the site. The frit patterns are specifically designed to provide a needed visual avoidance cue to birds in flight that glazing is present in their path.
Determining the extent of bird-safe glazing needed on a given building requires a comprehensive analysis of the window-to-wall ratio of each building façade, with a “Facade Zone” (FZ) and “Threat Factor” (TF) overlay. The FZ is based on bird flight elevation – Zone 1, which is from 0’ to 36’ above grade poses the greatest threat, while Zone 2 (above 36’) is considered half as dangerous for bird impact. The TF refers to the danger posed by building façade materials. The index ranges from 0-100, where zero is an opaque surface and one hundred is clear glass. Depending on the bird-safe frit pattern on the glass, the TF can typically be reduced to between 6-29. Based on the ratio between FZ and TF, an overall Build Collision Threat Factor (BCTF) is generated. A BCTF of 15 or lower is considered ideal; above 25 the building will endanger birds.
Learn more about the project here.