Properly functioning ventilation is a prerequisite for fresh and healthy indoor air. It removes impurities and brings in fresh, clean air as a replacement. Impurities can be caused by cooking or by other activities, radon gas from the ground, moisture, or chemicals from building and furnishing materials.

Ventilation is achieved by removing air from, for example the kitchen, toilet, washroom and walk-in-closet, and bringing in fresh air into the bedroom and living room. This way the fresh air is made to flow into the impure areas. It is recommended that ventilation is used constantly, at the very least on the lowest setting. The extent of the ventilation is suitable when the air changes once every two hours. A stuffy smell is a sign of inefficient ventilation.

What needs to be taken into consideration when designing a ventilation system?

When planning and designing a ventilation system, it is best to seek the advice of a professional, in this case the work is done according to rules and regulations. However, it is good to familiarise yourself with the options beforehand; do you care for a gravitational or a mechanical ventilation system.

When choosing a ventilation system the available options should be carefully thought through; it can be costly to change the system later on. Effecting factors are, for example the age of the building, the size of the building, the power and adjustment possibilities of the ventilation system, the level of automation of the device, location and the heat recovery capability.

Since the year 2013 building regulations have been updated; mechanical ventilation is required from newly built buildings (already since 2000 as heat recovery and exhaust air requirements). Regulations are applied in older buildings. More about the options available can be read here.

Gravitational or mechanical ventilation?

Gravitational ventilation is the most common method of ventilation in Finland. In newly built buildings it is used less. The reason for this is that gravitational ventilation might not provide enough air for all the rooms in the complex. However, the benefit of it is the savings in electricity consumption, due to the ventilation system being based on the pressure differences between the indoor and outdoor air.

Weather conditions have an effect: during the winter period the ventilation is at its greatest, and during the summer it is at its lowest, or virtually non-existent. An extra range hood can be installed for systems like this. The fault of the system is that the ventilation cannot be adjusted: there is a risk of the air flowing in the wrong direction or a lack of it completely.


Mechanical ventilation can be achieved in two ways. Firstly, a mechanical ventilation system for exhaust air can be installed to a gravitational ventilation system, or secondly, the ventilation can be done completely mechanically (both incoming and exhaust air). A mechanical ventilation system for exhaust air serves apartment buildings and is common in apartments, whereas fully mechanical ventilation is popular in single-family homes.

When using a mechanical ventilation system for exhaust air the air is removed with a blower, which can be located on the roof of the building. The incoming or replacement air can be taken care of by installing open-air valves, fresh air heaters, and window gaps. The weather hardly affects the efficiency of the ventilation, however the problem is getting enough incoming air to the living areas. Outdoor air can enter the building from leaks in the shell of the building, which brings draughtiness into the home. Compared to gravitational ventilation, mechanical ventilation consumes more energy.

Mechanical ventilation for both incoming and exhaust air has become more popular during the last decade or two. This can be seen in newly built homes, and is especially popular in single-family houses. When performing both indoor and exhaust air ventilation mechanically, it allows for better filtering of the air (a benefit for e.g. people with allergies) and heat recovery from the exhaust air. It is possible for apartment buildings to use per building or apartment systems. A ventilation system which is not regularly serviced can cause problems in the indoor air. When purchasing a ventilation system, it is also beneficial to consider other factors of the home, such as sound insulation.



How can I check the air leaks of my home?

A resident can check their home for leaks, for example by using the list below. The 20 most common leak points in newly built homes are listed as follows:

  • door seals, adjustments defective
  • the tape of the seams of vapour barriers in the ceiling
  • sealing in between the wall and ceiling
  • sealing in between the wall and floor
  • sheathing of foundations
  • insufficient sealing of electric wire inlets
  • seals of doors
  • sealing in between door frames and walls
  • sealing of the flue and ceiling
  • electric wire inlets, leakage point hidden
  • installation of ventilation or other ducts
  • wall tubes of electric cables
  • the upper side of the ventilation system
  • pipe feed-through in the flooring
  • holes in the vapour barriers in walls
  • sealing in between the intermediate floor and wall
  • the seam in between two exterior walls
  • holes in the vapour barrier of the ceiling
  • the base of the supporting post going through the exterior wall
  • the taping of the feed-through connection of the ventilation or other shaft

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