IMHO, as long as your ventilation is good, the coop is draft-free and your chickens are chosen well, you likely won't *need* heat. That said, since this coop is so close to your house, I would wire it for electricity and heat should you decide that you'd like to use it. It's so easy and that way it's ready to go at a moments notice should you get some freak weather.
I think it would be wise to hardwire a fixture (make sure it's exterior/metal or ceramic) by the roost. You can put a heat light in it for winter and then use a switch to turn it on/off as needed. And during the summer it can be used as a plain old light or not at all. And don't forget that you will need at least one electrical outlet in which to plug in a heated water dish so you can keep water fluid.
I have a winter page on my personal page if you're interested in checking it out.