We need air
We need ventilation in buildings and it must satisfy several different criteria.
It must be reliable, flexible and well-functioning, adaptable, and responsive to different needs and unusual events.
Ventilation needs to be provided for both people and buildings.
Basic principles of natural ventilation
Natural ventilation uses pressure difference that is caused by:
- difference between densities of interior and exterior air given by temperature difference
- wind velocity providing on windward façade positive pressure and on leeward negative pressure
Did you know?
Natural ventilation is also influenced by wind turbulance and flow pattern around a building (affected by neighbouring buildings, building exposure and building orientation).
Building shape also influences the natural ventilation, i.e. flow direction throughout the building and ventilation intesity.
Typical ways of natural ventilation
Aeration - air supply and exhaust is caused through inlets with proper high difference, i.e. inlet at the ground via openings and outlet via skylights in roofs. Typically used for industrial halls or stables. The ventilation is regulated by inlets and outlets openings.
Shaft ventilation - a combination of inlets via typically controlled window openings and shafts as outlets, creating a stack effect and using pressure difference in different heights. Typically used for multi-floor apartment buildings.
Other points to know about natural ventilation
Controls for natural ventilation can be based on sensors for indoor air quality, meteorological weather data and smart control/management systems.
Natural ventilation is often used for passive cooling at nights, where heat accumulated in the buildings throughout the day is vented out at night to avoid the building overheating.
Do you know?
Do you know that natural ventilation is historically the most widely used ventiation in residential and other types of buildings?
Today, buildings have modern windows that are airtight and efficient, so natural ventilation (via infiltration) is limited to only small amounts of air exchange and natural ventilation (via airing/windows opening) often takes too much effort for building occupants.
Therefore, today it is difficult to keep ventilation requirements using just natural ventilation.
Fundamentals of mechanical ventilation
Mechanical ventilation is one of the systems that keeps a habitable environment.
Purpose of mechanical ventilation:
- To heat or cool the incoming air
- To circulate/move the air in a room
- To supply/exhaust the required air amount in the room
Basic information about mechanical ventilation:
- Ventilation is operable independent on exterior conditions
- Requires precise operation control
- Provides temperature and humidity (and other sources) control
Mechanical ventilation is based on pressure difference and caused by dynamic pressure of a mechanical device - fan/blower.
Ventilation consists of 3 main parts:
- Ventilation rate – the amount and quality of the outdoor air
- Airflow direction – the flow of air within a building, from “clean” to “dirty” areas
- Air distribution – the delivery of outside air and removal of pollutants
Basic principles of mechanical ventilation:
- Overpressure ventilation
- Balanced ventilation
- Underpressure ventilation
Mechanical ventilation consists of several parts, i.e. air handling unit (AHU), ducts, air supply/exhaust devices, dampers, fan coils, heating/cooling unit, etc.