Here on our website, you'll see the rabbitry open at the bottom. We do this for ventilation for the summer time and nicer weather. It's great...not too much air, no drafts on the rabbits, usually. Since this winter is what it is, we stapled up gunny sacks all around the bottom. This still lets in air, but blocks the wind. When it's a nicer day, I will leave the door open and pull the gunny sacks back to allow air flow through the building. We have a few feed sacks that I put up only if the severe weather is coming, otherwise, that area is left open for ventilation. If you walk in to your barn or rabbitry and the ammonia smell smacks you in the face, you probably need to get things opened up somehow. That is NOT good for the critters.