What is a cost-effective method for providing outside ventilation air?

The HVAC connected outside air duct method is considered a cost-effective way to provide outside ventilation air because it integrates with existing heating, ventilation, and air conditioning systems. This method allows for a controlled and efficient intake of outside air, ensuring good air quality while minimizing energy loss.

By using the existing HVAC infrastructure, this method can increase the efficiency of air exchange without the need for additional equipment or structures. It allows for proper filtration and conditioning of incoming air, promoting improved indoor air quality while also reducing the likelihood of drafts and temperature fluctuations that can occur with less controlled approaches.

On the other hand, methods like window ventilation and the open-window method can lead to inconsistent air quality and may not provide adequate control over the amount and temperature of the incoming air, often resulting in higher energy costs due to heating or cooling principles being challenged. The portable fan method, while it can enhance airflow, typically lacks the efficiency of dedicated duct systems and can lead to unconditioned outside air entering the space without proper filtration or temperature regulation. Thus, the HVAC connected outside air duct method stands out as the most effective and practical choice for providing consistent and controllable ventilation.