What to consider
before choosing your
ventilation system?

In addition to the legal requirements that all residential ventilation systems must comply with, there are a number of qualities about a system that are worth taking into consideration when choosing your unit.

How high is the thermal efficiency?

According to the Danish BR18, ventilation systems for new builds and big remodelling projects must include heat recovery to minimise the amount of energy required to heat the home.

Thermal efficiency indicates how efficiently the heat exchanger in the system utilises the energy from the hot extracted air to heat up the cooler supply air. Thermal efficiency should be at least 80%. The higher, the better.

The Danish Knowledge Centre for Energy Savings in Buildings recommends using a heat exchanger with a thermal efficiency of minimum 85%.

Dantherm has efficient counter flow heat exchangers in both aluminium and plastic. Aluminium counter flow heat exchangers have a thermal efficiency of up to 86%, while the figure for plastic counter flow heat exchangers is up to 96%.

Get our full 32-page guide for selection and installation of residential ventilation right here: Selection Guide for residential ventilation

How high is the energy usage (SEL value)?

A ventilation system's SEL value is an expression of how much energy the unit uses to transport the air – 'the specific electricity consumption for air transport'. The Danish building regulations require the SEL value to be less than 1000 J/m3.

Can the system be equipped with an automatic fire safety controller?

In apartment buildings, it is sometimes preferable to let several ventilation systems share air intake and/or exhaust ducts. This reduces space requirements, since eight units share one large exhaust duct rather that having eight individual ones, for instance.

If this is the case, the system must fulfil some specific technical fire safety precautions, as defined in the Danish fire safety standard DS 428. This applies for instance to the installation of smoke detectors and fire dampers, so you avoid a possible fire spreading to other apartments via the ventilation ducts.

It is therefore crucially important that you make sure the system you choose is compatible with fire protection functionality. In Dantherm systems, a fire protection controller is an integrated part of the unit's basic control software, and if smoke and fire dampers are required, Dantherm's FPC can be added. For further information read the article "Residential ventilation with automatic fire protection control"

What type of exchanger is the better choice?

There are different ways of recovering heat from the air. Three of the best known methods are using rotary heat exchangers, cross flow heat exchangers and counter flow heat exchangers.

The counter flow heat exchanger is the most energy-efficient type, and has the added advantage of not leading odours around the building. A counter flow heat exchanger acts by allowing the hot extract air to pass the cooler supply air in the ducts, ensuring that the heat is transferred between the two airstreams without the supply air and extract air mixing.

For more information, please download Dantherm’s full Selection Guide for residential ventilation.