10 Tips for good ventilation design
A sign of good ventilation is that you don't notice it. A ventilation system that operates unnoticeably requires careful design, which involves paying attention to the characteristics of the building, the users and the purpose of use. Good ventilation is silent, consumes a small amount of energy and keeps indoor air fresh in all situations.
1. Hire a professional designer
Building a house is a strictly regulated process. According to the land use and building acts, if you start a building project, you have to take care of designing and constructing the building in accordance with the building permission and the related rules and regulations. A builder needs sufficient qualifications and competent people to implement the project. Because of this, you have to hire a principal designer who is responsible of the ventilation system of the house, for instance.
When an old house is renovated, the role of design is even more significant, for ventilation needs to be an unnoticeable part of the old building.
However, it is good if every house builder and renovator himself knows the many factors that have to be taken into account when ventilation is installed. The Finnish society of indoor air quality and climate (www.sisäilmayhdistys.fi) recommends that you write down the indoor air quality objectives in design documents by consulting manuals such as Classification of Indoor Environment 2008,
2. Correctly sized ventilation unit
When you choose a ventilation unit, it is essential to choose the size of the unit to match the needs. In normal circumstances, the ventilation unit must be able to change the calculated air volume once every two hours at about half power. This ensures that ventilation can be boosted if needed. In order to save energy it is also good if ventilation can be easily reduced when the dwelling is empty.
It has to be remembered, however, that dimensioning based on air volume is not always correct. The number of persons and functions also have an effect on the ventilation needed.
It is therefore important to use the number of persons as the primary starting point for the dimensioning of the outdoor air flow.
3. Automatic functions of the unit
It is sensible to adjust ventilation as needed in order to have the system consume as little energy as possible. If ventilation operates all the time at the same power, it is sometimes insufficient and sometimes too high. There are many options for controlling ventilation, from manual adjustment to fully automatic ventilation. Humidity and carbon dioxide sensors enable an intelligent home/away/boost automation: the amount of ventilation is adjusted depending on air quality, or the current humidity and carbon dioxide load.
4. Heat recovery capacity of the unit
The most important characteristic of a ventilation unit is its heat recovery capacity. It refers to the capacity of the unit to heat the air coming in with the heat from the air extracted. This means that less energy is required for the heating of cold outdoor air.
The best measure of the heat recovery capacity is annual efficiency. Annual efficiency has a large impact on the primary energy indicator and the actual energy consumption. You can calculate the annual efficiency of the ventilation unit by using the annual efficiency calculator provided by the manufacturer.
5. Location of the ventilation unit
The ventilation unit has to be located indoors, in a warm room with a temperature of at least +10 °C. The location of the ventilation unit is good when its sound does not disturb and its maintenance is easy. It is not nice to replace dirty filters in a walk-in closet, for instance. Moreover, as efficient heat recovery cells are big, a considerable space is needed for detaching them for cleaning.
A technical room, a warm storage or a utility room are good locations. Because of disturbing sounds, the unit must not be fixed on a wall next to a bedroom or living area. When choosing a location, you should also pay attention to the fact that the unit has many electrical connections, and also condensing water has to be drained.
6. Ventilation ductwork
It is recommended to build the ventilation ductwork as short as possible; a long and complicated ductwork is expensive and backfires as far as SFP and sound level are concerned. It is good if the ductwork can be installed in warm rooms indoors. Suspensions, intermediate floors, enclosures and partitions provide good routes for ventilation ducts. If all ducts are inside the vapour barrier, there is no need to insulate them thermally, nor are there any unnecessary holes in the vapour barrier.
Because of living comfort, it is also important to pay attention to attenuating the sound of the ductwork. Even if a sound level meets the regulated level, it can be disturbing in a bedroom, for instance. It pays to implement the sound attenuation of the ductwork with silencers located in the ductwork. In some unit types, sound attenuation can be implemented with a silencer part in the unit combined with duct silencers if needed. In addition, it is wise to make sure that the sound cannot travel in the structures from the technical room to bedrooms, for instance.
7. Installation location for the outdoor air duct
A fresh air grille located on a wall or below the eaves must be located on the cooler side of the house so that the sun will not heat the air coming in too much in summer. Furthermore, supply air should not be taken indoors in a place which is close to a dusty street. Exhaust air is led to the roof or from the wall to the outside if the local building supervision allows it.
8. Air circulation
For air to circulate in the whole dwelling, suitable circulation routes are needed. One way to ensure this is to have no doorsteps under doors. Alternatively, you can insert ventilation openings in doors or walls. Mechanical supply/extract air ventilation does not prevent you from having windows open or airing through windows. When ventilation has been planned properly, there is no need for window ventilation, for the unit brings clean filtered air into the living rooms. The best air quality in the living areas is ensured by leading supply air to the cleanest rooms, such as bedrooms in dwellings. From there it flows to the kitchen and the wet rooms and goes back to the outside through the discharge openings located in the rooms last mentioned.
9. Taking into use
When a ventilation system is bought, it is always necessary to agree with the supplier upon the adjustments for the system. Proper implementation of ventilation also involves guidance and information of the operating speed of the unit in order to ensure sufficient ventilation in different situations.
Check the cleanliness of the ventilation unit at an interval of 3 to 6 months. If needed, clean or replace the filters and remove other litter and dirt. In the course of time, you will learn to know the maintenance interval required by the unit, but many models also have a maintenance reminder. The filters should be replaced/cleaned in spring and autumn, but you have to replace them at least once a year. The need for maintenance depends on the residential environment.