Experimental Assessment of the Effects of Spacer Bar Design on the Condensation Resistance of Insulating Glass Units

Experimental and analytical assessment of three types of spacer bars used in making insulated glass (IG) units were performed and reported earlier, Elmahdy et al (1993). In that study, the authors presented the results of finite difference model and guarded hotbox measurements of the temperature distribution and overall U-factor of the three glazing systems. It was clear from that analysis that the so-called warm edge spacer bars demonstrated better thermal performance compared with conventional metal spacer bars. Consequently, IG units made of these warm edge spacer bars presented better units when it comes to their resistance to condensation, and hence thermal comfort. Following that study, new warm edge spacer bars appeared in the market place and it deemed beneficial to perform impartial evaluation of their performance particularly as related to the condensation resistance of the IG units made of these new warm edge spacer bars. This paper presents an experimental assessment of ten IG units made of ten different spacer bar types, which include conventional metal spacer and others currently available in the market place. The measurements were performed in a guarded hotbox according to a well-established test procedure, Elmahdy (1993), which applies the Temperature Index (TI) principles. Surface temperature measurements of the IG units indicated that there is a considerable difference of the glass surface temperature between units made with conventional metal spacer and those made with warm edge designs. The condensation resistance of IG units is determined according to the procedure outlined in the CAN\CSA A440 Windows standard, CSA (2001). The significance of the information presented in this paper is valuable because of the importance of the condensation resistance of glazing systems in harsh and cold conditions similar to that in the Canadian climate. This is also directly related to the comfort conditions in the built environment, which is in most cases affects the productivity of the inhabitants. More important is the direct benefit to IG manufacturers, where the information provides a clear demonstration of, and comparison of, the performance of the conventional and warm edge technology spacers.