@Sui that is a petwalk dog door. It’s the only passive house approved pet flap I’ve found. I’ve had dog flaps for years in various houses and been increasingly frustrated with how utterly crap they all are. They’re a security nightmare (I used to climb in our old one to scare the wife), always leak air like they’re not actually there and end up covered in mud and hair. The petwalk is electrotonically activated by rfid tags on the dog’s collars so there’s no need for them to touch it, sealed from the weather like an Austrian front door and is generally beautifully engineered. The dogs just approach it and it does the door man thing for them automagically. I even get a notification on my phone to say “Cassie opened the dog door from inside”. You can change how long it stays open for, get it to disable itself when its raining or trap them outside for a while if you need. It’s bloody brilliant.
When we moved in here, with it’s stupendously bad insulation, I couldn’t bring myself to hack a hole in the wall that I knew I was going to spend weeks sealing up with Kingspan, foil tape and new plaster, so I hid the exuberance in with some building materials. Quite a lot of building materials. Still, it was cheaper than a log burner…