During the coldest winter days, what percentage of outdoor air is typically used in a system designed for 12.5°C (55°F)?

In systems designed for specific temperature ranges, especially in colder climates, outdoor air percentage is significantly influenced by the need to maintain indoor air quality while minimizing heat loss. On the coldest winter days, utilizing a lower percentage of outdoor air helps to reduce heating loads, as incoming cold air can drastically impact indoor temperatures and energy consumption.

A typical system designed to operate effectively at around 12.5°C (55°F) for winter conditions would often employ around 15% of outdoor air. This amount is enough to ensure adequate ventilation while reducing the strain on heating systems. It balances between providing acceptable air quality and limiting the cold air entering the space, which is crucial for efficient heating.

The other percentages suggested may either introduce too much cold air, making heating less efficient, or be too low to maintain proper ventilation standards, which could affect indoor air quality negatively. Thus, 15% stands out as a practical compromise for such conditions.