Question

A mitigation strategy to combat urban heat islands is constructing white roofs to increase roof reflectivity. The low reflectance of a dark-colored roof causes heat to be absorbed, while the high reflectance of a white roof reflects energy away from the building.

The bar graph shows the amount of solar reflectance from different types of roofs, and the scatter plot shows the relationship between solar reflectance and the maximum temperature rise of each material in full sun conditions.
Use the graphs to evaluate the following statements.
Place True or False at the end of each statement.
A.) White coatings on roofs increase solar reflectance. True or False
B.) Gray asphalt shingles demonstrate greater temperature changes than white cement tile roofs. True or False
C.) Red clay tile roofs have a greater reflectance, and therefore a cooler temperature, than white cement tile roofs. True or False
D.) An increase in a roof's solar reflectance is correlated with an increase in the roof's temperature. True or False
E.) White coating roofs (1 coat - 20 mils) may experience a temperature rise of 5 degrees C, but gray asphalt shingles may experience a temperature rise of 37 degrees C. True or False

Answer 1

White roof coatings increase solar reflectance, leading to cooler roof temperatures, while darker colors like gray asphalt absorb more heat, resulting in greater temperature rises. The correct evaluation of the statements confirms this understanding of how roof colors affect solar reflectance and temperature.

Step-by-step explanation:

Evaluating the statements given based on the relationship between solar reflectance and the amount of heat absorbed or emitted by different roof materials reveals the following

A.) White coatings on roofs increase solar reflectance. True

B.) Gray asphalt shingles demonstrate greater temperature changes than white cement tile roofs. True

C.) Red clay tile roofs have a greater reflectance, and therefore a cooler temperature, than white cement tile roofs. False

D.) An increase in a roof's solar reflectance is correlated with an increase in the roof's temperature. False

E.) White coating roofs (1 coat - 20 mils) may experience a temperature rise of 5 degrees C, but gray asphalt shingles may experience a temperature rise of 37 degrees C. True

The rate of heat transfer by radiation is largely determined by an object's color, with black being the most effective at absorption and white the least. The higher the solar reflectance, the less heat is absorbed, resulting in a cooler surface temperature for materials like those used in roofing.

Answer 2

A) It is true that the White coatings on roofs increase solar reflectance. White surfaces reflect more sunlight which can help reduce heat absorption in buildings.

B) It is false that gray asphalt shingles typically absorb more heat than white cement tile roofs and leads to greater temperature changes.

C) It is false that red clay tile roofs generally have lower solar reflectance compared to white cement tile roofs, so they tend to be hotter, not cooler

D) It is false that an increase in a roof's solar reflectance is typically correlated with a decrease in the roof's temperature, as it reflects more sunlight and absorbs less heat.

E) It is true that white coating roofs may experience a smaller temperature rise (5 degrees C) compared to gray asphalt shingles which can experience a larger temperature rise (37 degrees C) due to differences in solar reflectance and heat absorption.