Hi Tomek,
Since one month I have an OpenTherm gateway running with the Openhab binding. I use this to monitor my Intergas boiler with Honeywell thermostat. Last Summer I soldered together an eBus monitor and monitor my Brink Renovent with the OpenHab eBus binding:
eBus binding.
I have tied them together with rules: When bathroom light is on and Intergas boiler is delivering hot water -> set ventilation to maximum. Furtermore I get the temperature readings from the Brink via eBus and use them for several other rules (and push the outside temperature from the Brink to display on my thermostat).
Recently someone has added support for Wolf CWL (basically a German branded Brink Renovent). So going eBus could be another way to look at your Renovent.
Krgds,
Cor