The manufacturers of ventilation units offer various options with their models.
Many units already have an integrated bypass, i.e. through and/or programming such as:
- Outside temperature is higher/lower than x°C
- Outside temperature is higher/lower than the room temperature by y°C
- Room temperature is higher/lower by z°C than the set temperature
nighttime supply of fresh air bypassing the heat exchanger.
Similarly, many units have an integrated electric preheating element so that the ventilation system does not cool down the warmed indoor air in winter. This can be counteracted, for example, by reducing the ventilation level.
As an accessory, many providers offer the option to retrofit an electric reheating element.
Some models even offer a hydraulic reheating element.
Some models can be purchased with an enthalpy heat exchanger (humidity recovery).
Some models can also be expanded with air quality, humidity, and CO2 sensors.
And, of course, as an option, e.g. pollen filter, radio remote control, etc.
Many models have a passive house certificate.
DIBt approvals are often applied for by the manufacturers, contact with the manufacturer is the only way to find out.
The two fans are usually controlled separately.
The 4Pa pressure monitor is required when using a fireplace in the house.
In some ventilation units, it is possible by changing parameters in the control system to run both fans absolutely synchronously and to cause the other to stop if one fan fails.
This is the trick with which some providers advertise to avoid the expensive 4Pa pressure monitor.
However, the final decision lies with the local chimney sweep. Usually, he just wants to look at the setting parameters on the system. For him, it is usually the combination of both devices (ventilation system and fireplace) that matters. A self-closing door on the fireplace is often the minimum requirement, regardless of the combination.
Tip: The regional fireplace sellers know the local chimney sweeps and their preferences. Before buying a fireplace, ask for an appointment with the chimney sweep; then there will be no problems with acceptance.
By increasing the ventilation level overnight, the building can be cooled down more strongly, or more fresh air can be had while sleeping.
Or if possible, when building with a basement, directly integrate a geothermal heat exchanger into the excavation. This prevents the indoor air from heating up so much during the day. Supply air on the north side of the building. Without a geothermal heat exchanger, reduce the ventilation level during heat.