In tropical climates, overcast skies are associated with what effect on heat gain?

• A. They increase heat gain due to reflected heat
• B. They decrease heat gain due to shading
• C. They have no effect on heat gain
• D. They reduce heat gain by shading

Answer: (A)

Under overcast skies, radiant heat transfer doesn’t drop to zero because clouds reflect and diffuse a large portion of the solar radiation that would otherwise escape. In tropical climates this diffuse radiation can still be substantial, and it is often redirected downward toward the building envelope. That means more radiant energy can enter through glazing and other exposed surfaces, increasing heat gain even though there’s no direct sun. Additionally, clouds trap some longwave heat near the surface, helping to keep outdoor and indoor temperatures higher. So, the overall effect is an increase in heat gain due to the reflected and diffuse radiant energy from the cloudy sky.