Title

Comparison Of Techniques For In Situ Nondamaging Measurement Of Solar Reflectances Of Low-Slope Roof Membranes

Keywords

Field measurements; In situ; Low-slope roofs; Pyranometer; Reflectometer; Solar reflectance

Abstract

With the implementation of the Energy Star Roof Products Program by the U.S. Environmental Protection Agency and the U.S. Department of Energy, techniques are especially needed that yield in situ measurements of the average solar reflectance of roof surfaces without damage to them. This paper presents results of limited field surveys with two types of instruments that permit such measurements. Solar reflectances on a scale from 0 to 1 were obtained by the established laboratory technique for five samples covering the range exhibited by low-slope roofs and coating systems for them. Based on these results, the average bias for one instrument, a portable solar spectrum reflectometer using a built-in light source, was +0.003. The maximum bias for the five samples was ±0.02. Scatter of readings over a roof area with this instrument depends upon characteristics of the specific surface. Scatter can be as little as ±0.001 but is typically more than ±0.02. The other instrument uses a pyranometer and is operated by recording the responses when the pyranometer faces the sun and when it is inverted facing the surface of interest. The reflectance is the ratio of the response when inverted to the response facing the sun. For a variety of roof surfaces, the average of readings with both instruments agreed within 95% confidence intervals of ±0.02 to ±0.06, calculated as ±t·s.d., where t is the t-statistic for the number of measurements and s.d. is the measurement standard deviation. © 2001 Plenum Publishing Corporation.

Publication Date

1-1-2001

Publication Title

International Journal of Thermophysics

Volume

22

Issue

5

Number of Pages

1613-1628

Document Type

Article

DOI Link

https://doi.org/10.1023/A:1012821827012

Socpus ID

33750671248 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/33750671248

This document is currently not available here.

Share

COinS