b'for 21 years, measured the high- and then tapered off over time. gone aging for less than five yearsboards in Figure 3, especially Sam- thislinearthermalperformance: est thermal resistance (R-5.5 perFigure 3 also compares NRCAwere less than the published LTTRples #2 and #3 that are close to thetheblowingagentresponseto inch). Because of blowing agenttest data representing the averagevalues. Based on these observationsLTTRtimeaverageperiodof15temperature and the replacement andmanufacturerformulationthermal resistance of aged insula- andfrom the realities that rooftopyears, the roofing industry shouldof blowing agent with air.variables,noclearrelationshiptionboards(one,twoandfourtemperature conditions vary signifi- givesomethoughttoNRCAsThetemperature-dependent could be established between in- years) that have been aged in con- cantly from LTTR-prescribed labo- recommendation. thermalperformancesofSam-sulation age and R-value. trolled laboratory conditions. Theratory conditions, NRCA does notFigure 3 shows the temperatureples #1, 2 and 4 were different TheresultingR-valueswereerror bars over the two- and four- view LTTR as being representativedependencyperformanceofthefrom the other samples. The data compared with the ASTM C1289year samples in Figure 3 provideof design R-value. NRCA recom- agedinsulationsamples.Exceptfrom these samples show an in-minimumthermalresistancere- therangeofthemeasureddatamends using an R-value of 5 perfor Samples #1, 2 and 4, the sam- verted crown profile (maximum quirements and the CAN/ULC- from the tested samples. inch in heating-dominated climat- ples showed linear thermal perfor- R-value at the mean temperature S704,Thermal Insulation, Polyure- TheintentoftheNRCAtestic zones for the purpose of roofmance (decreasing R-value with in- of 75 F and lower R-value at the thane and Polyisocyanurate Boards,data was to demonstrate R-values ofthermal design. Seeing the thermalcreasing mean temperature). Twomean temperatures of 40 F and Faced,minimumLTTRvaluetoinsulation boards that have under- performancesofagedin-serviceassumptionscanbemadefrom110 F). This profile is typical of provide a point of comparison.At a mean temperature of 75 F, ASTM C1289 provides an R-value per inch of insulation thick-ness of 5.6 ft2.F.h/Btu.in and 6.0 ft2.F.h/Btu.inastheminimumFigure 3requiredthermalresistancefor Type II, Class 1 and Type I in-sulationtypes,respectively.The thermal performance of the aged sampleswasbelowthisrequire-ment,whichwasexpected.The ASTM C1289 test protocol is for reportingthethermalresistance measurements of new boards that have undergone an early stage of aging. This early-stage loss of R-value is based on preconditioning foam samples at room tempera-ture(75F)for180daysbefore R-value testing at the mean tem-peraturesof75F.However,for comparison purposes, the R-val-ue of the in-service aged boards was three per cent to 30 per cent lower than the minimum require-ments of new insulation boards.Asimilarcomparisonwas made in Figure 3 with the CAN/ULC-S704 minimum thermal re-quirements.Theserequirements are based on LTTR testing report-ed at 75 F, where the loss of in-sulation R-value is dominated by blowingagentdiffusion.CAN/ULC-S704 provides a minimum LTTR value of 10.21 ft2.F.h/Btu for2-inchthickinsulation.Nor-malizingto1-inch-thickinsula-tion, the predicted LTTR value is 5.2 per inch, which is plotted in Figure 3 as the point of compari-son for Type I and II aged insula-tions. The comparison in Figure 3indicatesfiveoutofthe10 samples that are close to 15 years and20yearsoffieldagingare closetothisminimumrequire-ment. Although this comparison doesnt shed much light on the relation between published LTTR values (as it is not known for the samples) and actual aged five-year measured R-values, the data show there is a possibility the five-year actual R-value of the five samples must have been greater than R-5.2 Figure 3: Average R-value per inch of samples evaluated at three mean temperatures of 40 F, 75 F and 110 FORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 1 202013'