I read an article a long time ago, but the idea stuck in my head since then. The article was about a very obvious roof design to maximize heating and cooling, and if I remember correctly it was designed by a young boy no older than 14.
Here's how it was designed: The roof was basically set up like steps, with the vertical parts of the steps painted black and the horizontal parts painted white. The reasoning is that during the winter when the sun is lower and the rays will hit the vertical parts more, these black-colored vertical parts will absorb plenty of light and warm the house. Likewise, the horizontal white parts will reflect plenty of rays in the summer when the sun will beat down more directly.
I'm wondering about what will happen as snow melts on it, though. If I ever manage to pull off building the longhouse(s) I have planned, I think I'll incorporate this roofing design. Thought others would possibly be able to use the knowledge in their own endeavors.