Living on the edge: Improving curtainwall thermal performance

Twinsburg, Ohio
loupe level Space Needle
by Helen Sanders, Ph.D
loupe level Space Needle
High-performance PHSS warm-edge spacer was used to solve the thermal and structural challenges of the Space Needle renovation.
Credit: © Nic Lehoux

Meeting thermal performance requirements for curtainwall is increasingly challenging as codes are becoming more stringent. And it is becoming more difficult to trade off envelope performance with more efficient lighting and HVAC systems in performance compliance paths.

Silicone structurally glazed curtainwall systems typically have better thermal performance than their captured counterparts – all other things being equal. This is because thermal bridging associated with metal pressure plates and associated fasteners is eliminated. In the absence of an external frame, the major conduction path from inside to outside is directly through the edge of the glass. This means that the choice of spacer in structurally glazed systems has an outsized impact on the assembly U-factor.

If moving to structural glazing is not an option, exchanging the aluminum pressure plate with a non-metal version could be considered. Polyamide pressure plates can deliver a U-factor improvement of 20% in a thermally improved curtainwall system. Combining with a high-performance warm-edge spacer and wider thermal breaks can improve the performance further.

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