One of your home's most important components is its HVAC (heating, ventilation and air conditioning) system. No matter what type of climate you live in, the HVAC system in your home will greatly impact your quality of life. Happily hanging out in sunny Florida? Try making it though a steamy summer day with the central air on the fritz. Likewise, a New Englander would have a tough time making it through a January night without a good furnace.

Unfortunately, HVAC systems often aren't up to snuff. Frequently, they are asked to perform way beyond their capabilities. This is especially true in homes with additions. Most homes - especially older ones - were built with HVAC systems designed to adequately service the home's existing size, and that's it. If you have expanded your home, most likely you will also need to expand or upgrade your HVAC system.

Even if your system seems to be doing okay, you might still want to consider upgrading to a more efficient system. In the past few years, furnaces and air conditioners have made great strides when it comes to energy efficiency. Even if your unit is only 10 or 15 years old, you may see considerable energy savings by replacing it with a more efficient unit.

Depending on your situation, you may be able to simply add a supplemental heating/cooling source. For example, perhaps the spare room you added would be adequately heated by a small coal stove or even a space heater. However, for large additions, you will likely need to replace and upgrade your main HVAC system.

Brushing up on BTUs
When it comes to heating and cooling, everything revolves around BTUs. BTUs (or British Thermal Units) determine a system's heating or cooling capacity.

"Your HVAC contractor needs to do a heat loss calculation in order to determine your needs. They will estimate the heat loss and determine if you have enough existing BTUs," says Tom Kraeutler, co-host of "The Money Pit," a nationally syndicated radio show dealing with home repair and improvement topics.

Figuring out how many BTUs you need is not a simple math problem. You must take many factors into account, such as:

Factors to consider

1. The size of your home/room. 2. The height of the ceilings. 3. The number and location of windows. 4. The number and type of major appliances regularly in use.

Be leery of any contractor who "guesstimates" your BTU requirements too quickly, such as simply going by the square footage of your home. Many utility companies provide a service in which they will calculate BTU requirements for customers at little or no charge. Also, many BTU calculators are available online to help you determine your home's heat loss -- and your corresponding HVAC needs.