Designing a house to have low energy use is a three step process: keeping the heat where you want it (in when it's cold, out when it's hot), being efficient about what energy you do use, and offsetting that energy use when possible with the available heating or cooling the weather provides.
The following topics are background principles behind all heating systems design. While it isn't necessary to fully understand them, deeper understanding will make other topics make more sense:
Knowing heating principles, when can now proceed to building design:
We can now substitute some of the required energy with whatever heat from the sun and cooling from night air your site provides. This section also covers avoiding overheating in the summer.
The final step is to look at all the other uses of energy in the building, including their effect on heating and cooling:
Now that you know everything you need to know about energy use, we deal with the question of what are reasonable targets for energy use, by looking at few popular ideas on deep energy reduction: