A steel front door should have a thermal break, which is often a vinyl strip that separates the inside and outside door skins. This prevents cold from transferring through the frame and frost from forming on the inside surface. If you choose a replacement front door with glass or window ...
I hate skins. I hate screen protectors. I never use any of them. I have had every iPhone since the 3G, and only had a case on the 6/6S, because that thing was just too damned slippery. I had to buckle and get an Apple leather case. As soon as I got the 7, no more ...