My girlfriend and I bought a new house! And with it, an (older) Itho Daalderop CVE ECO 2SP mechanical ventilation unit. Itho Daalderop is a Dutch brand selling ventilation appliances and heating systems. I believe they mostly sell their products in The Netherlands. Figure 1. Our Itho Daalderop CVE ECO 2SP ventilation unit The above ventilation unit keeps the air in our house (specifically our bathroom, kitchen, and downstairs toilet) fresh by continuously exchanging indoor air with fresh outdoor air. It also came with a 868MHz RFT remote control to manually adjust the ventilation speed:

Here’s how to automate an Itho mechanical ventilation unit (e.g. CVE ECO 2SP) to auto adjust ventilation speed according to bathroom humidity levels.

All thanks to Arjen Hiemstra’s Itho WiFi add-on module (Dutch), and Home Assistant.