Which is a building practice to control heat flow?

• A. Increase R-value in areas with largest gradient
• B. Reduce interior noise
• C. Improve aesthetics
• D. Reduce air leakage

Answer: (D)

Controlling heat flow comes down to reducing unwanted air movement through the building envelope. When gaps around windows, doors, cables, and joints aren’t sealed, air leaks create convection loops that carry heat with the moving air. This infiltration and exfiltration can dominate heat losses in winter and gains in summer, so sealing leaks makes the entire system more energy-efficient and comfortable.

Reducing air leakage directly tackles this convective pathway, improving the effectiveness of insulation and the performance of the heating and cooling systems. Practices like sealing gaps, weatherstripping, and using airtight membranes cut down drafts and help maintain a steadier indoor temperature.

Increasing R-value helps resist heat flow through materials, but if there are substantial leaks, heat will bypass the insulation via air movement. The other options don’t address the main way heat moves through an occupied space, so they’re less effective for controlling overall heat flow.