LEED

Sustainable Design & the LEED Rating System


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 The Brick Industry Technical Notes

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Click here to download Technical Notes on Brick Construction No. 48

Solar Reflectance Values
for Phoenix Brick Yard

Intrinsic material properties can minimize the heat island effect.

Surface and air temperatures in urban and suburban areas tend to be higher than those in adjacent rural areas. This phenomenon, commonly known as the heat island effect, is the result of many factors, but the solar energy absorbed by the surfaces of pavement and buildings plays a major role. Because the heat island effect leads to increased demand for air conditioning and amplified levels of air pollution in cities, current and pending environmental rating systems for buildings encourage the use of construction materials that efficiently reflect solar radiation and emit heat via radian energy.

Solar Reflectance Index

The solar reflectance index (SRI) is a composite value calculated using the equations in ASTM E1980, “Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low-Sloped Opaque Surfaces.” For a given set of environmental conditions, SRI is based on a surface’s solar reflectance and emittance.

Target Values

Existing rating systems and a proposed standard provide incentives for building designers to use reflective hardscaping or roofing materials. For example, the Leadership in Energy and Environmental Design Green Building Rating System for New Construction (LEED-NC) provides Sustainable Sites (SS) Credit 7, “Heat Island Effect.” This system allows for one point (Credit 7.1) for using paving material with an SRI of at least 29 for a minimum of 50% of the site hardscape (including roads, sidewalks, courtyards and parking lots.)

Values for Phoenix Brick Yard Pavers.

Tested by Atlas Material Testing Technology

Paver Color

% Solar Reflectance

SRI

#01

44.6

53

#22

38.1

44

#46

34.4

38

#99

35.9

41

 

 
 
 
 
 

Hemispeherical Spectral Reflectance
and
Total Emittance Test Report

 

1.0     Introduction

This report represents results of special reflectance and total emittance measurements on the following four brick specimens coded:

#01
#22
#46
#99

 2.0     Test Methods and Procedures

Reflectance

Hemispherical spectral reflectance measurements were performed in accordance with ASTM Standard Test Method E903. The measurements were performed with a PerkinElmer Lambda 950 Spectrophotometer utilizing an integrating sphere (Fig A1.3 of E903). Total reflectance measurements were obtained in the solar spectrum from 2500nm to 300nm at an incident range of 8o. The measurements employ a detector-baffled, wall-mounted integrating sphere that precludes the necessity of employing a reference standard except to define the instrument’s 100% line. The measurements are properly denoted as being hemispherical spectral reflectance.

Total Solar p reflectance was obtained by integrating the spectral data against Air Mass 1.5 (ASTM G159) direct solar spectrum utilizing 105 weighted ordinates. All spectral data are submitted herewith in the original.

Emittance

Near-normal infrared reflectance measurements were performed in accordance with ASTM E408, Method A. A Gier Dunkle Instruments Infrared Reflectometer Model DB 100 was utilized for the measurements.

3.0     Observations, Deviations and Waivers

All measurements were performed on the top side of the specimen.

The values reported for emittance represent the average of at least four measurements.

With all test methods, there typically is a level of uncertainty for the test data due to the acceptable operating tolerances of the instrumentation and variation caused by the test method. The estimate tolerances are expected to be less than plus or minus 2% for most materials tested to ASTM E903.

 

4.0     Results

Reflectance and SRI:

Specimen Code

% Solar Reflectance

SRI

#01

44.6

53

#22

38.1

44

#46

34.4

38

#99

35.9

41