8 tips for designing a good ventilation system

A sure sign of good ventilation is that you do not notice it. These 8 tips give you a great start for designing the ventilation system.

An unnoticeable ventilation system requires careful planning. You should consider the building’s properties, the users and the purpose of use. A good ventilation system is quiet, consumes little energy and keeps the indoor air fresh in any circumstances.

1. Hire a professional to do the designing

Building a house is a strictly regulated process subject to law. According to the Finnish Land Use and Building Act, a party engaging in a building project shall ensure that the building is designed and constructed in accordance with building provisions and regulations and the permit granted. The party shall have the necessary competence to implement the project and access to qualified personnel. Therefore, a principal designer must be hired for the project who is, among other things, responsible for the ventilation system of the building.

When renovating an old building, the role of designing is emphasised even more in order to implement a ventilation system that is a seamless part of the old building. Every builder and renovator should, nevertheless, be personally aware of everything that must be taken into account when installing the ventilation system. The Finnish Society of Indoor Air Quality and Climate recommends recording the indoor climate goals in the design documentation. The Finnish Indoor Air Classification 2008 guide can be helpful in this.

Ventilation designers for one-family houses can be found in our map service.

2. Correct size of the ventilation unit

When choosing the ventilation unit, it is important to match the unit to the needs of the home. In normal circumstances, the ventilation unit must be able to replace the theoretical air volume of the home in two hours at approximately 50% power. This leaves room for boosting the efficiency of ventilation, if necessary. With respect to energy savings, it is useful to be able to easily reduce the efficiency of ventilation when the home is left unoccupied.

The choice of ventilation unit also depends on other outdoor air flow requirements that are determined in accordance with the use of the premises. For instance, a sauna in the home increases the total outdoor air requirement by 6 l/s, and if the area of a bedroom is over 11 square metres, outdoor air must be supplied to the room at a minimum rate of 12 l/s. Therefore, when choosing a ventilation unit, you should always turn to a professional to ensure that your unit is correctly dimensioned and compliant with the strict requirements.

3. Automation of the unit

It makes sense to adjust ventilation according to the need to ensure that the system consumes as little energy as possible. If the ventilation runs at the same efficiency all the time, it is sometimes inadequate and sometimes too efficient. There are many options available for controlling ventilation, from manual adjustment to full automation. Humidity and carbon dioxide sensors provide a smart at home/away/boost automation which adjusts the efficiency of ventilation according to the air quality, that is, the current humidity and carbon dioxide load. The Vallox MV ventilation units have integrated humidity and carbon dioxide sensors.

4. Heat recovery capacity

Heat recovery capacity is one of the ventilation unit’s most important properties. It indicates how efficiently the unit can heat the supply air with the heat recovered from the extract air, thus saving energy required for heating the cold outdoor air. Annual efficiency is the best indicator of heat recovery capacity. The annual efficiency is very significant for the E-figure and the actual energy consumption of the building. The annual efficiency of the ventilation unit can be calculated with the manufacturer’s annual efficiency calculator.

5. Location of the ventilation unit

The ventilation unit must be placed indoors in a place with a minimum temperature of +10°C. When planning the location of the ventilation unit, also consider the ease of maintenance. Replacing dirty filters in a walk-in wardrobe would not be very comfortable. In addition, efficient heat recovery cells are large and their removal for cleaning requires space.

Good locations include the utility services room, a warm storage room, the home utility room, etc. A wall bordering on a bedroom or living room is not a suitable place because of the noise. When choosing the location, also remember that the unit has many electrical connections, and a drain is needed for the condensing water. With respect to the newest unit models, it is also recommendable to connect a network cable to the unit, which should be taken into account beforehand.

6. Ventilation duct systems and the installation site of the outdoor air duct

The ventilation duct system should be made as short as possible: a long and complex duct system is expensive and has a negative effect on the SFP rate and the sound level. Specific Fan Power (SFP) is the total electrical power (kW) taken from the mains by the fans divided by the higher of the supply and extract air flows (m3/s).

It is preferable to install the duct system in a warm space indoors. Suspended ceilings, intermediate floors, enclosures and intermediate walls provide good routes for ventilation ducts. If all of the ducts are installed inside of the vapour barrier, thermal insulation is not needed and there is no need to make extra holes to the vapour barrier.

It is also important to pay attention to noise reduction in the duct system to ensure comfortable living. A sound level that meets the requirements may still be disturbing in a bedroom, for instance. The MyVallox ventilation units have low sound levels, but you should still ensure that sound cannot travel in the structures undesirably, such as from the utility services room to a bedroom. Use the Vallox MySelecta product selection software to check the sound level of your ventilation unit.

The fresh air grille installed on a wall or underneath eaves should be placed in the shadow on the cooler side of the house, so that the sun will not heat the supply air. Remember to also check that the supply air is not led in from a side facing a dusty street, for example. Exhaust air is led to the roof or out through a wall.

7. Air circulation

To allow circulation of air everywhere in the home, ensure a free route for the air by leaving out thresholds under doors, etc. Alternatively, you should make vents in the doors or walls to ensure the circulation of air. Mechanical supply/extract air ventilation does not prevent you from keeping windows open or airing the through the windows. However, with an appropriately designed ventilation system, window ventilation is not needed, as the unit supplies clean filtered air into the home.

The best air quality in living areas is ensured by leading the supply air first into the bedrooms, then to the kitchen and wet areas and from there out through the outlets.

8. Setup and maintenance

When you are buying a ventilation system, do not forget to discuss the adjustment of the system with the supplier. The appropriate setup of the ventilation system also includes instructing the user and informing them about the operating speed at which the unit works with adequate efficiency in different circumstances.

The ventilation unit must be checked every three to six months for cleanliness. When necessary, the filters must be cleaned or replaced, and other rubbish and dirt must be removed. Over time, you will learn to know the appropriate maintenance interval of your unit, but the MyVallox models also include a maintenance reminder. It is recommended to replace the filters twice a year (in spring and autumn), or more frequently if necessary. The living environment is one of the factors that the maintenance need depends on.