I'm sure everyone agrees...when it's too cold, the dogs should be indoors. But, if you find there are times the dog HAS to be outside, or it's something you're going to do anyway......then don't skrimp on construction. It has to be insulated. Build the house big enough that the dog can turn and lay comfortably...but small enough that it is as warm as possible after filling with straw..LOTS of straw. Our houses have double walls, floors, ceiling..with insulation inbetween. The house has to be raised off the ground. Face the door away from the wind. The best idea is to have an entrance...then a turn into the back. (you would want to be able to lift part of the roof to place straw, and clean in interior) If just a door opening...small as possible. We use heavy rubber strips that overlap as a door........blocks wind, but the dog goes in and out with ease. Our houses have an overhang.......keeps rain completely away from the door. Build the house where you will place it......believe me, when completed you will not move it. That's my 2 cents. IF you are building a doghouse....build it well. The 'bought' houses....no good at all except as a quick shelter from rain. You can use untreated lumber (you don't want the dog chewing on anything treated) since the floor is off the ground...if you cover the exterior (we used siding) and shingle the roof.