b'We made the following obser- tance was found to be consistent vations: irrespective of the insulation type. Effectivethermalresistance decreases with increasing gapEffect of Gap Offsetwidth. Within the two-layer staggeredEffectivethermalresistanceinsulation layout, the effect of the also decreases with increasinggap offset on the overall thermal gap height. performance of the roof assemblyThecombinationofgapalso was investigated. Two offsets, width and gap height lowers24inchesandsixinches,were the effective R-value. evaluated with the R-31 configu-The results show the presence ofrationforeachinsulationtype. gaps reduced the effective thermalFigure 3 provides the insulation resistance of the R-31 configurationthickness for each insulation type from three per cent to six per centto achieve the target design value depending on the gap features. of R-31. During roof system in-Tocomparetheperformancestallation, it is common practice ofthevarioustestedconfigura- to offset insulation board joints tions,theresultswerenormal- inthemultilayerinsulationlay-ized by examining the percentageout by 24 inches. The six-inch off-decrease in the effective R-valueset is the investigative parameter oftheassemblies.Itshouldbetocomparetheperformanceto notedtheresultsdiscussedherethe 24-inch offset. Figure 6: The effective thermal resistance of a roof assembly with gaps between the insulation.are a simplified analysis of actualFigure7showstherelation-resultstoshowrelativeeffectsshipbetweenaroofassemblys of thermal bypass and provide agapoffsetandoverallthermal comparison among the differentperformance.Assemblieswith test results. The gaps were devel- the six-inch gap offset showed an opedinasinglefour-foot-longaverageofthreepercentlower joint within a four- by four-footeffective R-value compared with assembly area. assemblies with the 24-inch offset The measured results in Figureirrespective of insulation type and 6 indicate the percentage decreasegap widths. The measured trend in effective R-value of an assem- waswithincreasinggapwidth, blyisfoundtobelinearwiththe overall thermal performance increasing gap height and width.of the assembly decreased. The ef-Irrespective of gap position, thefect of gap height also is visible in effective R-value of an assemblythe measured data. As gap height decreasedwithincreasinginsu- increased from 5.3 inches in poly-lationthickness(orgapheight).isocyanurateconfigurationsto Similarly, with higher gap widths,eight inches in stone wool con-the thermal performance showedfigurations, there was a decrease adecreaseineffectiveR-value.in overall roof assembly thermal For staggered gaps, the total gapperformance. The impact of gap heightisequaltothethicknessheight ranged from 4.7 per cent of insulation, and the measuredto6.2percent(averageoftwo data indicated the data trend re- gap offsets) decrease in the effec-mainsthesame:withincreasedtive R-value with 1/4 of an inch gap width and height, there is angap width and from 6.1 per cent increaseinthermallosses.Theto 8.2 per cent decrease with 1/2 decrease in effective thermal resis- of an inch gap width. Figure 7: Effect of gap offset in staggered joint configuration.+Build SolutionsTotal Design F architek.com | 1 888 317 9226or Your Green Roof Projects.ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 1 202115'