What must all mechanical ventilation systems include according to the guidelines?

All mechanical ventilation systems must include specific openings for intake and exhaust to ensure proper air flow and circulation within a building. These openings are crucial as they allow fresh air to enter the space and enable stale air or contaminants to be expelled. This setup helps maintain indoor air quality by preventing the accumulation of moisture, odors, and pollutants which can negatively affect the health and comfort of occupants.

In contrast, focusing only on energy efficiency ratings does not address the fundamental need for ventilation. Manual controls may limit the effectiveness and convenience of the system, while restricting ventilation to kitchens and bathrooms ignores the requirements for proper ventilation throughout the entirety of a building. Thus, ensuring appropriate openings for both intake and exhaust is essential for the effective functioning of mechanical ventilation systems, promoting both indoor air quality and the overall efficiency of the system.