I’m much more of a cat person than a dog person and some provision needs to be made for cats in the new development. Passivhaus and cat flaps are generally incompatible – more due to the air tightness requirements than the thermal insulation – so initially I was thinking the cats would be accommodated in the outbuildings rather than in the main house. However, since there will be no outbuildings for a while I need to think again.

Fortunately there is a solution in the form of the Pet Walk pet door. It’s very expensive but it has clearly been designed with Passivhaus applications in mind. (It’s from Austria, home of a surprisingly large number of Passivhaus components.) In particular:

• It passes the standard air tightness tests and performs as well as any other door or window
• It’s very well insulated as standard with extra insulation (for the frame) available as an option
  • The advice from my Certified Passivhaus Designer is that it’s not necessary to model it separately since it performs as well as whatever wall or door it is installed in
• It opens automatically (via a motor drive) in response to motion detectors and / or RFID chips
• It locks securely and can be integrated into an intruder alarm system

Pet Walk pet door, http://www.petwalk.at/

Plan A was to install it in one of the walls, but with the walls being so thick (250mm cavity plus 2 x 100mm concrete blocks) that would require quite a long and wide “tunnel”, so Plan B is to install it in the side door. It would have been ideal if it would have fitted in the fixed side-light by the door but that is too narrow so it needs to go into the door itself. In some ways that will complicate matters, especially with respect to the 24V DC power supply, but a simple “door loop” can take care of that, as well as the integration into the alarm system.

One good feature is the wide range of clip-on covers that can make the inside and outside blend in with a variety of colours and surface finishes. They’re available in the same colours as the Internorm doors.

Update 2016-03-20: I have now purchased this cat flap in advance of it being fitted by the door installers. I’m not going to use the supplied plug-in power supply but instead hard-wire it using a separate 24V DC power supply and door loop. The supplied plug-in unit is rated 24V 1.0A so I am going to use a Mean Well DR-30-24 which mounts on a DIN rail and is rated 24V 1.5A.

The instructions say to cut off the supplied DC line socket when using a hard-wired power supply but I prefer to connect using a DC line plug (especially since I have several available). The correct size is: 5.5mm diameter with a 2.5mm pin and roughly 11mm long. The centre pin is positive.