A few outdoor housing questions

Wondering if people can help me please.
We're In the process of building the bunnies outside home and just want to make sure we have everything right.

1. If I insulate the inside kennel do I need to add some kind of ventilation, I'm worried they would suffocate if I closed them in, the door will be a locking cat flap.
2. How easy is it to get bunnies to use a cat flap for the first time? I'm a bit worried about Alice she's not very adventurous and VERY small.

Thanks in advance

Yes, you will need to add some ventilation,not sure if some vents would do it.
Mine don't have a cat flap but they soon got used to the runaround tunnel, you could maybe tape it open or not put the door on at first until she is used to going through the hole maybe, that's what I did for my cat anyway :thumb: