Potential for thermal breakage of sealed double-glazing units

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Series titleCanadian Building Digest; no. 129
Physical description6 p.
Subjectthermal stresses; sealed glazing units; crackings ( breaking); breakage; windows; heat reflecting glass; heat absorbing glazings; Heat performance
AbstractBoth panes of factory-sealed double-glazing units are susceptible to thermal breakage. The outer pane experiences large thermally induced stresses when solar radiation falls on the sealed unit in cool weather. The breakage potential is even greater for units with heat-absorbing or heat- reflecting glass in the outer pane than for units with a clear outer pane. The inner pane experiences a high thermal stress when the outdoor air temperature is very low and the unit is subjected to localized heating. The breakage potential of the inner pane is greater for heat-reflecting units with a low U-value than for clear, heat-absorbing, or high-emissivity heat-reflecting units. Measured and calculated values of thermal stress for inner and outer panes of sealed glazing units indicate that thermal stress by itself should not cause glass breakage. Extensive breakage failure will only occur if the thermal stress is augmented by other tensile stresses or if weak or damaged glass is used. In the absence of a reliable method of predicting the probability of thermal breakage in sealed units, however, all factors that can possibly reduce the potential for breakage should be accommodated in design. This is especially true for units with heat-absorbing and heat-reflecting glass.
Publication date
PublisherDivision of Building Research. National Research Council Canada
AffiliationNRC Institute for Research in Construction; National Research Council Canada
NoteAussi disponible en français : Possibilités de bris d'origine thermique des vitrages doubles scellés
Peer reviewedNo
NRC number1781
NPARC number20327627
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Record identifier19fbd0ae-ab83-4682-ad1f-fa9e4afdba10
Record created2012-07-18
Record modified2016-05-09
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