What is the heat gain in BTU/hr for a dark colored commercial roof in Wilmington, NC, on a summer design day?

• A. 1500 btu/hr
• B. 2000 btu/hr
• C. 2981 btu/hr
• D. 3500 btu/hr

Answer: (C)

To determine the heat gain in BTU/hr for a dark-colored commercial roof in Wilmington, NC, on a summer design day, several factors must be considered, such as the solar radiation received, the roof's color and material properties, and local climate conditions.

In regions like Wilmington, which typically experience high temperatures and significant solar exposure during the summer, a dark-colored roof can absorb much more heat compared to lighter-colored roofing materials. This increased absorption leads to a higher internal heat gain which needs to be calculated for energy efficiency and HVAC load purposes.

The correct calculation for a dark roof on a summer day incorporates the intensity of solar radiation—which is quite high in North Carolina—along with specific heat gain coefficients related to the roofing material's color. In this scenario, the specified heat gain of approximately 2981 BTU/hr accurately reflects the combined effects of these variables. It is a reasonable estimate based on established calculations for heat gain under similar conditions.

This level of heat gain would typically necessitate adequate cooling measures in the building’s HVAC design to maintain comfort and energy efficiency, particularly in a commercial setting where occupancy and equipment loads increase the demand for cooling. The importance of understanding these calculations is paramount for HVAC professionals in designing effective systems tailored for specific climates and