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Unit power
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When a ventilation unit is chosen, it is vital to base the choice on the needs in the dwelling and to make sure that adjusting is possible. In normal conditions, it is necessary for a ventilation unit to exchange air in the dwelling once in two hours at 50 to 60% power. Ventilation can then be boosted during summer nights or reduced when the residents are out for a long time.
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Automation
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Another matter to be decided when choosing a unit is the grade of automation. There are ventilation units where adjustment is mechanical, and units that automatically adjust power based on readings given by a humidity sensor in a washroom or a carbon dioxide sensor in the bedroom, for instance.
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 Digitally controlled Vallox Digit SE ventilation units automatically keep indoor air at desired setpoints on the basis of carbon dioxide or humidity content in air and prevent wasted ventilation and unnecessary consumption when the dwelling is empty.
Heat recovery capacity of the unit
Heat recovery capability is an important characteristic of a ventilation unit. This means heating incoming air with the heat coming from air being extracted, thus saving energy needed for heating cold outdoor air. In summer, this phase is bypassed.
As much as 20 to 50% of energy consumption in a house comes from ventilation. It is highly important to do everything possible to restrain consumption: to distribute air flows into the dwelling in an appropriate fashion and to choose a unit which results in sufficient ventilation at approximately half power and which has the capability of efficiently recovering heat. There are distinct differences in energy efficiency between ventilation units on the market.
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Location of unit
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The ventilation unit has to be located in a warm indoor room, with a temperature of at least +10 °C, where it does not disturb living and where maintenance operations are easy to do if needed. Good locations include a utility room, a warm storehouse or a laundry room. To prevent disturbing sounds, the unit must not be fixed on a wall next to a bedroom or living area.
When choosing a location, attention should also be paid to the fact that the sound of the unit is the louder the greater the power used is. In addition, using the unit requires electricity and condensing water needs to be drained. Post-heating may also be water-based.
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 The sound of ventilation can be influenced through unit location, ductwork silencing and the choice of unit. In the new Vallox 95 Silent unit, sound coming through the envelope is lower than normal by 5 to 6 decibels.
Ventilation ductwork
For silencing of the ductwork, silencers located in the ductwork provide an economical solution. In some unit types, silencing can be implemented by using a silencer within the unit and possibly adding duct silencers if needed. The mounting of silencers is easy during the construction stage, but doing it afterwards is expensive and difficult. Silencers have a significant impact on the comfort of living.
In terms of duct location, it has to be considered whether to put them in a warm or cold space. In the latter case, insulation is needed.
The choice of duct material is a matter of taste. Plastic ducts have become common thanks to their easiness, but as e.g. the local extract duct in the kitchen must be made of steel, this material remains popular in other ducts, too.
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Air intake point
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A fresh air grille located on a wall or below the eaves must be located on the cooler side of the house as the sun heats exposed air too hot in summer. Furthermore, supply air should not be taken indoors near a dusty street as it would mean bringing impurities indoors and into the system. Extract air should be led to the roof.
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Air circulation
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As supply and extract ventilation is the natural ventilation in the house, it must be ensured that air can circulate freely in the whole dwelling. In other words, air needs circulation routes. Therefore, there must not be doorsteps that make a wall air-tight, or ventilation openings have to be inserted in doors or walls.
Mechanical supply and extract ventilation does not prevent you from keeping windows open or ventilation from the windows. However, keep in mind the energy escaping from open windows in winter and the pollen coming indoors in spring. Properly designed ventilation brings in clean, filtered air to the living area, from where it proceeds to the dirty area and goes out.
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Taking into use
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Properly designed ventilation also encompasses proper guidance in using the ventilation system. When a ventilation system is bought, also the adjustment of the system must always be agreed upon. This is an easy way to find out the operating speed needed for exchanging air once in two hours.
A suitable power level can also be determined by testing, but the starting of ventilation is considerably easier when the supplier of the unit and the system informs the customer of the normal adjustment positions and advises how to implement them according to the plan.
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Maintenance
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The cleanness of the unit must be inspected at three to six month intervals, and when needed, the filters have to be cleaned or replaced; any litter and dirt must also be removed. With time, you learn to know the maintenance frequency required by your unit, but for example Digit type Vallox units have an indicator which give a maintenance reminder at e.g. four-month intervals.
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 The filters should be cleaned every spring and autumn, but at least once a year. The frequency of maintenance depends, among other things, on the residential environment and allergies of the family members.
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Connections of liquid-circulating post-heating
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- VKL Connections (..pdf, 0,76 Mt)
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