Theodore Lentz, Nathaniel Huygen and John Sanders
Theodore Lentz, Graduate Research Assistant, National Brick Research Center, 100 Clemson Research Blvd, Anderson, SC 29625, United States, telentz@g,.clemson.edu
Nathaniel Huygen, Research Assistant, National Brick Research Center, 100 Clemson Research Blvd, Anderson, SC 29625, United States, nhuygen@clemson.edu
John Sanders, Director, National Brick Research Center, 100 Clemson Research Blvd, Anderson, SC 29625, United States, jpsand@clemson.edu
ABSTRACT
Solar reflectance is an important property for any building material because it dictates the thermal energy absorbed from solar radiation. An increase or decrease in thermal energy entering the
building could increase energy consumption from HVAC units depending upon the local climate. There are many ASTM methods that can be utilized to measure solar reflectance. However, some of these test methods can be problematic to use due to limitations in their testing procedure. Testing completed using direct exposure to the sun have a limited time window for testing, are affected by current weather conditions, and require a large sample. Testing using portable solar reflectometers have a limited number of detectors, leading to an incomplete representation of infrared solar reflectance. To avoid some of these potential limitations a novel solar reflectance testing method was developed. This testing method uses a hot box apparatus to promote uniform boundary conditions and a calibrated infrared camera to measure the surface temperature of the sample. This method also uses a solar simulating light that is applied to the exterior surface of the sample. The energy absorbed from the light by the sample is then determined using an energy balance equation. This allows the solar reflectance to be measured based on surface temperature as opposed to the magnitude of reflected light. Several commercial bricks with varying colors and surface textures were characterized using this testing method. This was done to determine the relationship and correlation between the two properties and the solar reflectance. Testing has shown that darker colors or rougher surface textures result in lower solar reflectance values. Testing with this method has shown that changes in surface roughness can result in up to a 9% change in total solar reflectance.
KEYWORDS: solar reflectance, surface roughness, color, hot box apparatus
