The insulation (R-value) of your home determines how much temperature you lose to the outside. A common approach uses thicker studs that allow for more insulation. However, the studs themselves remain uninsulated. External insulation greatly increases your home insulation and also protects against other maladies.
Conventional appraisers see traditional fireplaces as a huge value-add to the selling price of a home. However, from a heating and cooling standpoint, a fireplace is essentially a window that is always open. An artificial fireplace provides much of the ambiance of a traditional fireplace but doesn't have the associated heating and cooling loss, it eliminates the need to buy firewood, and is ready at the flick of a switch.
Traditional single pane windows are very poor insulators. Double or triple-pane windows trap gas on the inside of the window, proving a much greater insulation value while maintaining beautiful vistas. In LilyPad, the windows that can swing open are double-pane, while the fixed windows are triple-paned. This is due to the increased weight of triple-paned windows are less suitable for moving.
Most homes have a single thermostat so Dad might be trying to keep the heater off to save money while Mom will be shivering because she runs cooler. This can be solved by allowing individual control of heating set points for each room. Also, by insulating the interior walls as well as having great overall external insulation, your home will be perfect and comfortable for everybody.
Building orientation is another critical factor to capture the most passive solar sunlight in the winter, while avoiding excessive heat in the summer. A conventional subdivision has building lots with a variety of North/South orientations. When choosing a lot and designing a building for it, it’s important to note which side will be south-facing (in the northern hemisphere) to capture the most passive solar heat.