Track 1: Decline vs. Revival: Tempering the Impulse to Tear Down and Start Over
APT Student Scholar Abstract
High-performance retrofits of Mid-Century Curtain Wall: A case study analysis of opportunities to enhance thermal performance using low-impact, reversible solutions.
Tuesday, September 25
8:30 AM - 10:00 AM
Location: BNCC- 101AH
Laura Blokker, Program Assistant Director – Tulane University
American International style glass buildings face tremendous obstacles to their perpetuity, especially considering their poor thermal performance. The non-thermally broken frames and single-pane glass conduct higher rates of heat intensity across the envelope’s section, which leads to inadequate thermal comfort, higher building operational costs, and accelerates decay through excessive expansion, contraction, and condensation. Holistically, the subsequent deterioration precipitates safety issues, higher maintenance costs, and higher building energy usage – all of which places pressure on building owners to remove and replace the old curtain wall with new systems.
This study’s objective is to identify modifications that improve the curtain wall’s insulating performance for the purpose of preserving the existing glass envelope, improving envelope thermal performance, and encouraging sustainability through the reduced environmental impacts achieved by the building’s continued use. This research discusses opportunities for envelope enhancement through a comparative investigation of three American, mid-century case study buildings:
Lever House, located in IECC Zone 4, New York, New York;
Ford Motor Company, located in IECC Zone 5, Dearborn, MI;
New Orleans City Hall, located in IECC Zone 2, New Orleans, Louisiana
This study’s methods employ energy simulation analysis software THERM 7.4.14 and WINDOW 7.4.14, developed by Lawrence Berkeley National Laboratory, to model two-dimensional heat-transfer effects in cross sections of the curtain wall framing components. Material assemblies are custom created in the software per original building drawings. Each case study analysis is localized to the curtain wall’s typical “module”, which is the typical arrangement of mullions and glass that repeats to compose the whole facade. The module energy analysis is simulated for the existing baseline and the proposed retrofits, which are evaluated per the following incidences:
Total System U-factor
Solar Heat Gain Coefficient
Visual Light Transmittance
The study results show that a combination of noninvasive modifications both improves upon the baseline and meets the modern standards of the International Energy Conservation Code. In order to optimize performance, the enhancement design is specific to the regional climate and follows either a passive solar heating or solar control strategy. The retrofits investigated include glazing treatments, new supplementary interior glazing panels, and conceptual detail best practices. The glazing treatments considered include surface applied films, chemical tints, and low-emittance coatings. This new assembly is reversible, provides an “insulating” air space between the existing and new frames, provides a glazing surface that can be treated with a high-performance coating, and can be hidden behind the existing glass curtain wall so as not to detract from the original exterior appearance. Ultimately, the retrofit scenarios seek to extend the envelope’s usable life, render a higher-performing envelope, and offer a sustainable and economical solution that considers preservation and building functionality.
- Understand typical decay mechanisms caused and influenced by high rates of thermal conductance through glass envelopes and define the typical problems faced by historic curtain walls.
- Define a standard approach methodology for evaluating the baseline thermal performance and proposing enhancement modifications using THERM, WINDOW, and referencing the International Energy Conservation Code.
- Understand the conceptual technical detailing approach for enhancement modifications in a solar control dominated climate and a passive solar heating climate.
- Use industry-leading, open-source software available from Lawrence Berkeley Laboratory for use as an effective tool for evaluating the efficacy of the enhancement modification.