Heating and cooling systems are the largest energy consumers in most homes. This means you can reduce your energy bills greatly if you can reduce your heating and cooling energy needs. Passive solar heating is a good way of increasing your house's temperature to reduce the HVAC's load and the associated energy consumption:
Install Large South-Facing Windows
Installing large south-facing windows allows maximum solar radiation to reach your house. In fact, the sun's orientation during the winter season (when the sun is low in the sky) maximizes the amount of sunlight entering the house through the windows. Just make sure that the windows are efficient so that they don't lose any of your house's heat when they are closed. To help keep the house cool during the hot summer days, you need to have roof overhangs so that the sun, which will be high up in the sky during this time, doesn't get inside the house.
Embrace Thermal Mass Flooring
Thermal mass is a measure of a materials response to temperature change. Materials with high thermal mass are able to absorb considerable heat and retain the; in short, they don't lose heat easily. Therefore, when you use a material with high thermal mass on your floor, it will absorb the sun's energy during the day, and it won't lose it easily. The material will only lose the heat slowly during the night when the heating effect of the sun is no longer there. These materials may also help with cooling since they tend to keep cool as long as they aren't exposed to direct heat (such as direct sunlight). Examples of flooring materials with high thermal mass include concrete, stone, ceramic, and other dense materials.
Add a Trombe Wall to Your House
A trombe wall is a conventional masonry wall that is separated from the exterior atmosphere by a glass wall. The design allows the wall to absorb maximum solar heat and release it into the house's interior. The masonry wall should be painted black for maximum heat absorption. The space between the masonry wall and the glass wall contains air, which helps to prevent heat loss since air isn't such a good conductor of heat.
Most of these are things that are best incorporated into a house's design during construction or renovation. A combination of passive heating systems and home energy management will go a long way on reducing your heating and energy usage in the house.