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Aged Thermal Resistance (R Value) of Foil-Faced Polyisocyanurate Foam Thermal Insulation Board by Morton Sherman

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Aged Thermal Resistance (R Value) of Foil-Faced Polyisocyanurate Foam Thermal Insulation Board by Morton Sherman AGED THERMAL RESISTANCE (R VALUE) OF FOIL-FACED POLYISOCYANURATE FOAM THERMAL INSULATION BOARD BY MORTON SHERMAN ABSTRACT AGED THERMAL RESISTANCE (R VALUE) OF FOIL-FACED POLYISOCYANURATE FOAM THERMAL INSULATION BOARD The aged thermal resistance (R value) of gas-barrier quality aluminum foil-faced polyisocyanurate foam thermal insulation board has been determined in ASTM C236 guarded hot box tests conducted in three qualified testing laboratories on full-size boardstock. Common-lot materials were measured in 1976 (15 to.33 months after manufacture) and retested in 1978-9 (47 to 68 months after manu­ facture). Analysis of results indicates: 1. Essentially no change in.R per inch thickness over this extended (15 through 68 months) period of time after product manufacture with or without glass fiber reinforcement. 2. Demonstrated low order magnitude of change in average R per inch from one month after manufacture (8.34) to time-aged plateau .(7.04): approximately 15%. 3. The linearity of aged R value with product thickness at three mean temperatures: a. 7.81 R/inch at 400F mean temperature. b. 7.04 R/inch at 750F mean temperature. c. 6.39 R/inch at 1100F mean temperature. 4. A linear relationship between R/inch and insulation mean temperature; an increase of 0.021 R/inch with each OF decrease in mean temperature, in the temperature range investigated. 5. Confirmation of the precision capability of the ASTM C236 Guarded Hot Box test method conducted in three NVLAP-accredited testing facilities: individual laboratory averages within 5% of three-laboratory averages; three-laboratory averages with coefficients of variation within 2.5 to 3.6%. Morton Sherman Senior Research Associate Jim Walter Research Corp. St. Petersburg, Florida 33702 002 Ever since the initial development of halocarbon-blown rigid polymeric foam therma 1 i nsu1 ati on ma teri a 1sin the 1950' s, much has been reported in the techni ca 1 1iterature concerni ng the so-ca 11 ed "aging" effect on the therma 1 insulation characteristics of these materials. Capable of init~a1 manufac­ ture with k-factors in the range of 0.11 to 0.13 BTU Inch/Hr Ft of, months of storage in ambient air can result in increased k-factors and reduced R values. It is generally accepted that a combination of physical mechanisms, particularly ambient air permeation into, and halocarbon gas diffusion out of the foam cells, result in reduced halocarbon gas concentrations within these cells and correspondingly poorer thermal resistance characteristics. The rate and magnitude of this change is greatest for unfaced low density foams, and least for halocarbon-blown rigid polymeric foams encapsulated by gas-barrier quality metal at the time of manufacture. A major objective of the studies reported here was to confirm the particu­ larly effective performance of gas-barrier quality aluminum foil facers laminated at the time of manufacture to the two major surfaces of rigid urethane-type foam insulation boardstock, in terms of the small order of magnitude of k-factor and/or R value change with such protective surfaces, and their ability to maintain this protected R value over a significantly long period of aging time. A secondary objective of these studies on common-lot foil-faced po1yisocyanurate foam insulation boardstock was to quantify the ability of the ASTM C236 Guarded Hot Box test method to pro­ vide thermal resistance measurements on full-size product with a satisfactory and reproducible degree of between-laboratory precision. Foil-faced po1yisocyanurate foam insulation board products are large-di­ mension laminated panels composed of gas-barrier quality aluminum foil facers directly bonded in the product manufacturing process to ha1ocarbon­ blown po1yisocyanurate foam material which may also contain distributed glass fiber reinforcement. Foil-faced po1yisocyanurate foam products, when applied in accordance with manufacturer's instructions, can meet the requirements of the major model building codes, many insurance authorities and other regulatory bodies, in a wide variety of applications. Foil-faced po1yisocyanurate foam products should only be used in accordance with recommended uses and application instructions. The use of these products, or other thermal insulations, in conjunction with other combustible building components which are exposed, may contribute to rapid spread of fire. Foil-faced po1yisocyanurate foam products with distributed glass fiber core reinforcement, or these products used in conjunction with non-combustible building components, may not con­ tribute to rapid spread of fire. The above conclusions are based upon fire tests conducted on unoccupied structures and upon nationally recognized fire tests. Foil-faced po1yisocyanurate foam board with distributed glass fiber core reinforcement is suggested for use as an exposed wall and/or ceiling insu­ lation in agricultural, commercial and industrial buildings, such as factories, warehouses, agricultural structures, parking garages, mercan­ tile establishments (stores), aircraft hangers, cold storage structures, tennis courts, skating rinks, riding arenas, etc. Foil-faced po1yisocyanurate foam insulation board is suggested for con­ cealed use in residential construction having an interior finish (such as gypsum wallboard) acceptable to local building codes. Examples of suggested concealed uses are: 1. High performance insulation sheathing in new frame wall construction. 2. Thin profile cavity wall insulation in new masonry construction. 3. High performance insulating/vapor barrier undercourse behind new interior wall and/or ceiling finish material. 953 4. Thin profile insulating underlayment beneath roof shingles in vaulted ceilings and "A" frame construction. 5. Underslab or perimeter thermal insulation. 6. Retrofit - thin profile insulating underlayment behind new exterior siding. 7. Retrofit - thin profile insulating undercourse behind new interior finish acceptable to local building codes, In this study, the thermal resistance of aged full-dimension Thermax (TF-600) and Technifoam (TF-200 and TF-400) insulation boards produced during 1973 through 1975 and stored in an unregulated but weather-sheltered storage area at our facility in St. Petersburg, Florida, were measured in accordance with ASTM Standard Method of Test C236, "Thermal Conductance and Transmittance of Built-Up Sections by Means of the Guarded Hot Box". Tests were conducted at: Dynatherm Engineering, Lino Lakes, Minn.; Dynatech RID Co., Cambridge, Mass.; Jim Walter Research Corp., St. Petersburg, Fla. All three testing facilities are accredited for technical and professional competence in conducting ASTM C236 tests under the National Voluntary Laboratory Accrediation Program (NVLAP). The Dynatherm test assembly, shown in Figure 1, utilized a 20 square feet metering area measuring 4 feet by 5 feet within a 6 feet by 7 feet guarded hot box opening. The Dynatech test assembly, shown in Figure 2, utilized an 11.41 square feet metering area measuring 3.97 feet by 2.87 feet within a 6 feet by 6 feet guarded hot box opening. The Jim Walter Research test assembly, shown in Figure 3, utilized a 36 square feet metering area measuring 6 feet by 6 feet within an 8 feet by 8 feet guarded hot box opening. All test assemblies utilized wood frame mountings and taped or caulked joints for convenience in test panel installation into the hot box opening and the elimination of uncontrolled air leakage paths as a possible source of error. The results of these guarded hot box tests, conducted in two separate sub­ missions of common-lot materials to these three testing laboratories are shown in Table lA, lB and le, Summary Tabulation. Initial testing was con­ ducted in 1976 on boardstock ranging from 15 to 32 months of age; retesting was conducted in 1978 and 1979 on resubmitted boardstock specimens, now ranging from 47 to 68 months of age. Mean temperatures of 40F and 7SF, and also 110F in the retesting series, were selected to provide additional product performance information for design purposes. Because this testing program documented the significant influence of mean temperature on the magnitude of measured R values for these exceptionally efficient thermal insulation materials, it is important to note here that mean temperature specifications of ± 0.5F were requested and achieved with­ out particu'lar difficulty in the retesting series, as compared to ± 5F requested and achieved in the initial test series. Shown in these tabulations for each product tested at each mean temperature at each testing facility is: product identity and age from time of manufac­ ture, average product thickness, measured R value and calculated R value per inch of product thickness. Three-laboratory averages, standard deviations and coefficients of variation for each mean temperature condition are summarized at the bottom of these tables. The linearity of aged product R values obtained in both test submissions vs. average product thickness, is shown in Figures 4, 5 and 6. At 40F mean temperature, individual data points are shown together with the line of their average, 7.81 R per inch. The same information is shown for 75F mean temperature with an average R per inch of 7.04, and 1l0F mean tempera­ ture with an average R per inch of 6.39. 954 The equivalency of aged R values per inch of product thickness obtained in both test submissions (indepe~dent of the specific reporting laboratory) vs. product age in months, is shown in Tables 2, 3 and 4. At 40F mean tempera­ ture, individual data points are
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