A Burning Question Revisited

Fire Testing of a Glazed Spandrel with Spray Foam Insulation

Overview

Abstract

In recent decades the use of unitized glazing systems has become increasingly common especially for high-rise construction. The opaque panels in unitized glazing systems have traditionally been insulated with mineral wool insulation installed within the aluminum frame behind a glazed spandrel. The interior face of the mineral wool is typically flush with the interior frame and finished with a foil facer or a galvanized sheet metal back pan.

Increasing code requirements for energy efficiency of opaque wall assemblies has led to the common practice of providing an additional layer of insulation inboard of the unitized glazing system. In colder climates, however, the practice of insulating inboard of the unitized glazing systems raises the concern of condensation on the surfaces of the glazing system now shielded from exposure to the interior heat source. This risk is further increased if the assembly inboard of the unitized glazing system is not airtight and the interior insulation is not in continuous intimate contact with the interior face of the unitized glazing system. The increased risk of condensation is especially elevated in residential buildings with their higher levels of interior humidity, limited ventilation and increasingly a lack of perimeter heating. The application of spray foam on the inboard face of glazing systems has been used in recent years as one means of mitigating the risk of condensation.

The use of foam insulation as part of building enclosures has received increased scrutiny in recent years and numerous envelope assemblies have been successfully tested to CAN/ULC S134 or its US counterpart NFPA 285. However, most of these assembly specific tests have been performed on stud wall assemblies. The following builds on a previous paper describing the testing of metal panel spandrel with interior spray foam insulation and outlines the results of testing spray foam insulation inboard of the glazed spandrel a unitized glazing system. It demonstrates how these assemblies can also meet the requirements of these standards.


Authors

Photo of Stéphane Pierre Hoffman

Stéphane Pierre Hoffman

shofffman@morrisonhershfield.com

Morrison Hershfield now Stantec

shofffman@morrisonhershfield.com


Keywords

Introduction

The use of foam insulation as part of building enclosures has received increased scrutiny in recent years and numerous envelope assemblies have been successfully tested to CAN/ULC S134 1 or its US counterpart NFPA 285 2 . However, most of these assembly specific tests have been performed on stud wall assemblies. The following builds on a previous paper by Hoffman and Kayll 3 and outlines the results of testing spray foam insulation inboard of a unitized glazing system with glazed spandrels. It demonstrates that these assemblies can also meet the requirements of these standards as well as the previous test on spandrels with metal panels.

Background

In recent decades the use of unitized glazing systems has become increasingly common especially for high-rise construction. The improved quality from off-site assembly of these manufactured systems along with their

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Why Spray Foam Insulation?

The application of spray foam on the inboard face of glazing systems has been used in recent years as one means of mitigating the risk of condensation. The spray foam

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CAN/ULC S134 vs NFPA 285

Both CAN/ULC-S134, “Fire Test of Exterior Wall Assemblies”, and NFPA 285, “Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components”, provide a

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Window Wall Assembly Description

Window walls are different from curtain walls in that they bear on the slab edge rather than being hung outboard of the slab edge like a traditional curtain wall system

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Challenges of Testing a Unitized Glazing System

When it came to undertaking CAN/ULC S134 testing of the unitized window system, there were a few challenges to overcome. The first had to do with the configuration of the

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Instrumentation

The instrumentation documented in the test report †8 are summarized here. Three water cooled heat flow transducers were installed 3.5 meters above the top of the window opening: one within

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Findings

Testing was performed in accordance with the CAN/ULC-S134 test method. Once ambient conditions were met the burners were ignited. Per the specified method a 5 minute flame growth period was

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Conclusion

The results of this test demonstrate that, despite some challenges in adapting the erection of the window wall assembly to accommodate the requirements of standard and the nature of the

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Footnotes

  1. CAN/ULC-S134-2013 “Fire Test of Exterior Wall Assemblies” Underwriters Laboratories of Canada.

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  2. NFPA 285-2019, “Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components”, National Fire Protection Association

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  3. Hoffman, S. P., Kayll, D. “A Burning Question: Fire Testing of a Window Wall System with Spray Foam Insulation”, proceedings of the International Institute of Building Envelope Consultants Building Envelope Symposium, 2020

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