In order to understand the areas that energy efficient retrofits (fixes) should be installed, it is first necessary to understand the different energy zones in the home
Conditioned Areas
"intentionally" heated and cooled. These areas are also called living areas. Examples are the living room, kitchen, bedrooms, etc. . . Some "clubbed" basement are conditioned if they have air distribution vents or heating pipes "intentionally" installed in them. Any ducts in these areas should be duct sealed.
Unconditioned Areas
Unheated Areas are just as they sound, they are areas that have no heat source running through them. One of the most common is an attic. If a basement, attic, or crawlspace have a heating or cooling distribution system "that is insulated or wrapped", these areas are considered unheated. Attics should have ~18 inches of insulation and crawl spaces 6 inches and both should be air-sealed.
Unintentionally Conditioned Areas
Unintentionally Conditioned Areas are areas that do not have distribution system that are intended to heat or cool the areas, "but" they are heated or cooled by uninsulated pipes or ducts. Many basements that have furnaces in them, are examples of these. The pipes and ducts in these should be insulated, but ducts should be sealed by qualified people first.
Air Sealing
Air sealing is one of the easiest way that you can save hundreds of dollars a year with just a minimum of investment. Many times you only need caulk, foam and drywall or R-Max board. Heat seeks cold and wherever you have a crack or hole, heat will be drawn out like a vacuum in the winter and drawn in the summer. These are called, "air infiltration areas". These areas are usually in the conditioned areas. "Bypasses" are areas in unconditioned or unintentionally conditioned areas that create a air draw or vacuum up the chases or wall cavities of the home. This vacuum helps to draw energy out of your house. One you can find now is in your basement. In most homes if you go to where the chimney cavity goes up the wall and look up, you will see gaps or a hole where the concrete and the wooden floor meets. This chase goes all the way up to the attic. Not only is this a fire hazard for flames in the basement can be drawn up the house, to set the attic ablaze, but this chase is "sucking" energy out of your house, up to the attic. IT MUST BE SEALED!!! Your house is full of these leaks and a Blower Door or infrared scan can HELP you find them.. Air sealing and duct sealing go hand in hand for as much as 70% of your duct work could be a hole to the great outdoors. Pressure Pan Testing and other methods will find these in a Green Energy Audit. Ask you auditor if they can provide these services.
Insulation
Insulation will be one of the costliest and most labor intensive part of your "Home Energy Investment". The best way to determine if it is cost-effective is to preform or have preformed an energy audit. Since all types of insulation have different "R-Values", it is important to determine the type of insulation you have and the depth of it. Sometimes it is cost-effective to take attic insulation to 14", depending on your weather climate and the cost of the material and labor. An audit can give you a way to determine if your possible $1,000.00 investment will pay itself back in 3, 5, or 7 years. In some cases you may save $500.00 per year for 20 years or a return of $10,000.00. The price of an audit is almost always worth itself in savings.
Basement: ceiling, walls, ducts, hot water pipes, steam pipes and hot water heaters in many situations need to be insulated. Attics and the ducts running through them need a certain level of insulation to stop the heat transfer through your ceiling or sheetmetal duct. Kneewalls and sidewalls in many situations need to be insulated. Crawl spaces in almost every situation need to be insulated and have a vapor barrier. The ultimate goal is to turn unintentionally conditioned space into unconditioned space and to stop heat transfer through the conditioned shell. Our audit will describe all these situations.
Low Cost Energy Improvements
There are numerous low cost energy items that you can purchase and be garanttee a direct payback. They include: Low-Flow Showerheads, Low- Flow Faucet Aerators, Hot Water Heater Insulation, Pipe Wrap for hot water, Plastic for your windows, Weatherstripping and Door Sweeps for your doors, Foam (sponge) for fixed windows with air conditioners, Filters for your heating/cooling system, Furnace Cleaning and Tuning, Water Dams for your toilet tank, Energy Efficient Light Bulbs (Even though you may feel strange paying over $30.00 for a LED light bulb... they last 20 years and may save over $500.00... they only use ~15 watts of power and give off much better light), etc... These are just a few low cost energy improvements, so you may want to contact your local hardware store for more ideas.