Passive versus Mechanical Ventilation
Hybrid ventilation combines mechanical ventilation with passive ventilation to optimize IAQ, thermal comfort and energy conservation. Ventilation’s purpose is to provide acceptable indoor air quality and thermal comfort. Most residential buildings ventilate using both passive ventilation and mechanical ventilation.
Passive ventilation includes the following.
- Educated building occupants
- Unintentional air leakage
- Opening and closing windows
- Supply and exhaust grills
- Ventilation stacks
- Use of prevailing winds and the stack effect to move air
Mechanical ventilation systems include the following types.
- Exhaust only ventilation systems
- Supply only ventilation systems
- Balanced ventilation systems, including heat recovery ventilators and energy recovery ventilators.
Hybrid ventilation uses both passive ventilation and mechanical ventilation in one system. Advanced hybrid ventilation, which includes intelligent controls, can achieve a balance between indoor air quality, thermal comfort, energy consumption, and electric peak load.
Hybrid ventilation can reduce both electricity consumption and electricity peak demand. It provides more options for local control and minimizing fan energy when the outdoor climactic conditions are favorable.
Adaptive Thermal Comfort (ATC)
Occupants who enjoy more control of their indoor environment may tolerate a wider range of the indoor temperature. Adaptive thermal comfort is an idea based on an occupant’s connection to the outdoors and control over their environment. This connection and control allow occupants to adapt to a wider range of thermal conditions than normal. The greatest opportunity for energy and power savings may come from hybrid ventilation’s ability to provide adaptive comfort. Research indicates that building occupants appreciate some level of control of their thermal comfort and indoor air quality. The more transparent, simple and responsive the ventilation system, the better the occupant feels through adaptive comfort.
Adaptive thermal comfort can reduce the energy consumption of heating, cooling, and ventilation systems in residential buildings. ATC includes the following strategies.
- Provide education about comfort and allow a sense of control
- Open and closing windows and blinds
- Don and shed clothing to affect comfort
- Make only necessary adjustments to HVAC systems
The dwelling’s residents can maintain good indoor air quality by using local mechanical ventilation together with opening windows and doors. Depending on climate and season, residents can control natural ventilation to provide clean air, thermal comfort, and energy efficiency.