It is warmer outside than inside. Warm air would come in by:

It is warmer outside than inside. Warm air would come in by:

• A. Conduction
• B. Infiltration
• C. Convection
• D. Radiation

Answer: (B)

Warm air entering a building through cracks and openings is infiltration. When outside air is warmer than inside, it tends to move indoors if there are gaps around doors, windows, vents, or other joints. This inward air movement is driven by pressure differences created by wind, temperature differences (stack effect), and mechanical systems, allowing the outside warmth to mix with indoor air and raise indoor temperatures. Infiltration is the practical path for air entry, distinct from conduction (heat transfer through solid materials) and radiation (heat transfer by infrared waves). It’s also the general idea behind convective heat transfer, but infiltration specifically refers to the unwanted air leakage that brings warm outside air inside. Reducing infiltration by sealing gaps helps improve energy efficiency.

Warm air entering a building through cracks and openings is infiltration. When outside air is warmer than inside, it tends to move indoors if there are gaps around doors, windows, vents, or other joints. This inward air movement is driven by pressure differences created by wind, temperature differences (stack effect), and mechanical systems, allowing the outside warmth to mix with indoor air and raise indoor temperatures. Infiltration is the practical path for air entry, distinct from conduction (heat transfer through solid materials) and radiation (heat transfer by infrared waves). It’s also the general idea behind convective heat transfer, but infiltration specifically refers to the unwanted air leakage that brings warm outside air inside. Reducing infiltration by sealing gaps helps improve energy efficiency.