Calculating the Effect of Infiltration on Indoor Temperature Stability

by

Understanding how infiltration affects indoor temperature stability is crucial for energy efficiency and comfort in buildings. Infiltration refers to the unintended air leaks through cracks, gaps, and openings in a building’s envelope. These leaks can lead to significant heat loss in winter and heat gain in summer, making temperature regulation more challenging.

What Is Infiltration?

Infiltration occurs when outside air enters a building through small openings. This process is driven by pressure differences caused by wind, temperature differences, and mechanical systems. Unlike ventilation, which is controlled and intentional, infiltration is often unintentional and can vary depending on weather conditions and building design.

Impact on Indoor Temperature

Infiltration can significantly affect indoor temperature stability. During cold weather, infiltration causes heat to escape, increasing heating demands. Conversely, in hot weather, it allows warm outside air to enter, raising cooling loads. Quantifying this effect involves calculating the heat transfer due to infiltration, which depends on the air change rate, temperature difference, and the building’s volume.

Calculating Heat Loss Due to Infiltration

The basic formula for heat loss (Q) through infiltration is:

Q = ρ × V × n × cp × ΔT

Where:

  • ρ = air density (about 1.225 kg/m3)
  • V = building volume (m3)
  • n = air change rate per hour (ACH)
  • cp = specific heat capacity of air (about 1005 J/kg·K)
  • ΔT = temperature difference between inside and outside (K)

Reducing Infiltration for Better Stability

To improve indoor temperature stability, buildings should minimize infiltration. This can be achieved through sealing cracks, installing weatherstripping, and ensuring proper insulation. These measures reduce heat transfer and help maintain a consistent indoor environment, saving energy and increasing comfort.

Conclusion

Calculating the effect of infiltration on indoor temperature involves understanding air exchange rates and heat transfer principles. By quantifying infiltration’s impact, architects and engineers can design more energy-efficient buildings and implement strategies to enhance indoor comfort and stability.