Recent developments in glazing manufacturing have resulted in the introduction of a variety of glazing systems to meet the consumers demand and, in many cases, with better thermal performance than conventional glazing. Insulating glass (IG) units are now available where air is replaced with argon and other heavy gases (or mixtures of gases), low emissivity coatings on glass or plastic films, and muntin bars in the cavity between the sheets of glass. Muntin bars are made of various materials such as aluminum (anodized or painted), vinyl, or silicone foam. Although muntin bars are used for aesthetic reasons, they may cause adverse effects on the IG units performance, which may be attributed to the improper preparation of the muntin bars or the use of inferior paints. Ultraviolet (fogging) tests were performed on a number of argon-filled IG units with and without muntin bars. The test results indicate that most of the IG units with muntin bars fail the UV test when viewed at off-angle. Meanwhile, when viewed at right angle, most of the IG units with muntin bars passed the UV test. Test results also showed that the R-value and condensation resistance of IG units with muntin bars are 4% to 7% lower than those units without muntin bars. The thermal bridging effect of the muntin bars contribute to the lower glass surface temperature in the area adjacent to the muntin bars.

Units: SI