Here’s what you need to know about steel curtain wall systems to get started on your next project.
U-values measure thermal transmittance across a glass façade system, with lower ratings corresponding to better insulative performance. Standard curtain wall systems often achieve U-values between 0.25 and 0.50. For high-performance systems, those values can reach as low as 0.19.
It is important to understand that several variables can influence a glass wall system’s U-value—most notably the glass but also the framing material—and that thermal performance goes beyond this one measurement.
Given the area of glass used in a curtain wall system, the type of glass has the biggest impact on U-values. Double-, triple- and even quadruple-glazed lites and the way they are fabricated can all increase or decrease a glass wall system’s ability to resist thermal transmittance.
But framing, too, can significantly contribute to better insulated buildings.
For instance, steel frames have a lower thermal transfer rate than traditional aluminum frames, which mitigates thermal bridging, or when a wall component acts as a conduit for temperature transfer. Frames with lower thermal transfer rates can help project teams keep U-values low for increased efficiency. It also reduces the number of thermal breaks a system may need, streamlining the entire design.
Image by Simon Hurst Photography
U-values are only one measurement of how a curtain wall system may contribute to sustainability goals.
For instance, Solar Heat Gain Coefficients (SHGC) measure how much solar radiation is transmitted through a glazing system. Lower SHGC ratings mitigateincreases in indoor heat during sunny days throughout the year. This is another crucial measurement for designing efficient buildings.
As LEED v5 becomes more integrated into design practices, certified buildings, very broadly, will need to be almost 20 percent more energy efficient than LEED v4 certified buildings—strictly from the differences in requirements for compliance with ASHRAE Standard 90.1-2019 instead of ASHRAE Standard 90.1-2010. This will place added importance on how all the performance metrics of a glass façade system work together to support energy efficiency.
Technical Glass Products (TGP) hosts several AIA-registered courses that help architects navigate sustainable building practices, fire-rated design and much more.
