How do we ventilate?

Ventilation moves outdoor air into a building or a room, and distributes the air within the building or room.

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.

Natural or mechanical?

The air exchange from outside to inside of buildings happens in these ways - naturally or mechanically:

  • Unintentional via air leakages from windows, doors, and various holes such as joints and cracks in the building envelope.
  • Intentional via natural ventilation, through opening windows/doors and air vents for deliberate venting by people and for people.
  • Proper mechanical/hybrid ventilation, to add additional and controllable airflow within buildings to provide a good indoor environment.

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.

How ventilation works?

Ventilation requires air flowing between interior and exterior. Thus it is necessary to start and maintain air flow according to requirements in a ventilated space. Basically pressure difference is a force starting an airflow.

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.

Important terminology used in mechanical ventilation

Under the principle of the human right to health, everyone has the right to breathe healthy indoor air.
The Right to Healthy Air, World Health Organisation, 2000