Winter Camping - how warm on the inside of your Popup TC

Only pop up that I'm aware of with a 'slide out' and it's not really a slide out but rather a fold out sleeping space is the Northstar. No one else does that and I agree, most pop up TC's will be smaller. In actuality, a good thing because they are geared toward limited camping and seasonal use but surely can be used in the winter, no issue so long as one follows some common sense guidelines that apply to all RV's in the winter, not just a pop up TC.