A major area to seal against air leakage to improve heat loss is which of the following?

• A. Windows
• B. Insulation
• C. HVAC Equipment
• D. Lighting

Answer: (A)

Air leaks are a major path for heat to escape or outside air to enter a building, so sealing the envelope around openings makes the biggest impact on reducing heat loss. Windows are a common culprit because gaps around the frame, sash, and corners let drafts slip through even when insulation inside the walls is good. If you seal these leaks—caulking around stationary parts, weatherstripping movable sashes, and ensuring tight door/window perimeters—you cut a lot of unwanted air movement and keep warm air from slipping out.

Insulation inside walls helps with heat retention by slowing conduction, but it doesn’t stop air from sneaking through gaps. HVAC equipment and lighting aren’t direct seal points for air leakage, so they don’t address the leakage path the way sealing around windows does.