5.1 Heat buildup of polymeric building products due to absorption of energy from the sun may lead to distortion problems. Test Method Test Method D4803 was developed to predict a building product’s heat buildup (temperature rise). It compares the relative temperature changes of a pigmented PVC product and a PVC panel containing carbon black when exposed to an infrared heat lamp. Based on experimental results that determined the maximum temperature for this black panel under both solar exposure and in the laboratory test, a method for determining the exterior temperature rise and heat buildup for a test panel was developed. This test has shown to be useful and reliable but is time consuming and requires controlled conditions to minimize sources of variation.

5.2 This test method uses a spectrophotometer to measure a specimen’s reflectance in the ultraviolet, visible, and near infrared region and uses the spectral power distribution of the heat lamp specified in Test Method D4803 to determine an intensity factor, which is an index of the relative spectral energy absorption by the specimen.

5.2.1 The temperature rise that would occur under an Test Method D4803 test is proportional to this intensity factor. An equation has been derived from the correlation of the intensity factor and temperature rise data obtained from Test Method D4803 testing of samples with a wide range of color and lightness. A total of 99 samples were studied and represent samples with the lowest to highest temperature rise. Linear regression analysis yields a R2 correlation coefficient of 0.98.

5.2.2 The procedure in Appendix X1 allows prediction of temperature rise that would result from testing of the same sample under Test Method D4803.

5.2.3 As this procedure is a correlation to results obtained by Test Method D4803, it is a method that yields a relative temperature rise compared to black under certain defined severe conditions, but does not predict actual field application temperatures of the product. These product temperatures are influenced by incident angle of the sun, clouds, wind speed, insulation, installation behind glass, etc.

5.3 The intensity factor itself is a dimensionless index of the relative energy absorption of the specimen, without conversion to a temperature rise. It can be used to compare the heat buildup characteristics of different colors, or different candidate formulations for the same color. It can also be used to categorize color into ranges of intensity factor, to be used as a basis for testing of full siding products for resistance to thermal distortion.

1.1 This test method uses reflectance spectra from the ultraviolet, visible, and near infrared region to produce an index of the temperature rise of polymeric siding above ambient temperature that occurs due to absorption of the sun’s energy.

1.2 The test method determines the intensity factor of a sample color. The intensity factor is a function of the sample’s reflectance spectra and the energy output of the heat lamp used in the test method Test Method D4803.

1.3 Appendix X1 provides a method for using the intensity factor to determine the maximum temperature rise of a sample under severe solar exposure.

1.3.1 A correlation between intensity factor and heat buildup (temperature rise) as predicted by Test Method D4803 exists.

1.3.2 The heat buildup (temperature rise) for a polymeric building product specimen is determined from its reflectance spectra and the correlation’s regression equation.

1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.