Following our "House Posts", enjoy it.
Another effect that we should discuss is how your furnace or boiler delivers heat to your house. Most furnaces and boilers run either at full fire or off. When the combustion cycle starts, a certain amount of heat is used to warm up the heat exchanger and the duct or pipes. When the furnace or boiler shuts off, much of this heat will be lost.
(Having your ducts taped and insulated will help minimize this.) Any energy-saving strategy should also try to minimize the cycling of your heating system.
The most energy-saving alternative is to let your house become as cold as possible while you’re not home. What’s “as cold as possible”?
Don’t allow anything fragile (water pipes, for example) to freeze.
Allow just enough time for your heating system to bring the house temperature to its set point the moment you walk in the door.
But wait, there’s another complication. Even though the air temperature in your house may be at the perfect set point, you may feel less comfortable under these conditions. That’s because the surfaces in your house will probably be colder than if you had left the temperature set point higher. Cold surfaces will make you feel colder—not just because of touch (conduction), but also because of radiation.
The strategy of saving energy by allowing your house to drop in temperature while it’s unoccupied makes perfect sense. Programmable thermostats can “learn” how fast your house heats up and bring the temperature to the set point with little cycling. Also: Web-enabled thermostats, where you can access your home system from any Internet-connected computer, offer even more convenience for people with varying schedules.