Transparency vs. Efficiency: Glass Facades

The Commons serve as the gathering place of the New Science Center at Amherst College. This communal space extends into the teaching and lab spaces on the interior of the building and extends outward to the campus Greenway. The campus-facing wall of the Commons is primarily glass, which allows for views of the activity within and connects the users back to campus.

A large wall made mostly of glass presents a few performance challenges and to overcome them, we employed a collaborative approach to develop integrated solutions. Together with our engineers and product manufacturers, we studied and developed a number of systems and strategies tackling heating energy and peak cooling load reduction as well as ensuring thermal and visual comfort. We did this with an eye to the project’s goal of creating a welcoming and largely transparent space for the campus.

Three studies in particular leveraged the collective knowledge of the team, as well as the use of advanced simulation tools, to analyze and inform decisions which addressed performance and supported the design.

First, our daylighting consultant (Integral Group) used optical data from LBNL’s Window program to develop HDR renderings through Radiance which accurately conveyed how the human eye would perceive our curtain wall under a number of sky conditions. Using this data along with the samples received from various manufacturers, allowed us to find a glazing assembly that balanced performance with optimal light transmittance and limited coloration and reflectance.

Radiance simulation

Glass sample mockup

Second, again leveraging data from our daylighting consultant, along with our own in-house analysis (using a REVIT –> Rhino –> Ladybug –> Excel workflow), we were able to develop a shade control strategy which preserved transparency and views while controlling glare, addressing thermal comfort and reducing the peak cooling load in the space.

Finally, using data pulled from our energy model (OpenStudio), mechanical load model (TRACE) and actual system performance data from the manufacturer’s test laboratory, we created several CFD shoebox models to assess the performance of the proposed heating and cooling systems as well as study thermal comfort in the space. Through this process we determined that the radiant panels originally specified for the project required more convective flow resulting in a change in the design.

CFD Analysis

Radiant wave mockups.