How To Size A Boiler Or A Furnace For A House You are thinking of replacing your boiler or furnace and you need to know what size system you need. Boilers and furnaces are sized according to BTU output. First let's make sure we know the difference between a boiler and a furnace. A boiler is so named because water inside the unit is heated by the burner and when the water reaches a certain internal temperature, is released and circulated through the baseboard system. A furnace contains no water and uses a "heat exchanger" within the furnace unit. The burner's flame then heats the element and a blower forces the heated air through a ductwork system with air vents. For boiler sizing, the BTUs required output is a function of the length of the baseboards for all heating zones of the house. The formula to determine the correct size boiler is as follows: measure the linear footage of all the baseboards in all the rooms of the house; add up the total length of the baseboards; then multiply this by a factor of 600. This figure will give you the amount of BTUs required to heat the house. For example, assuming you measured a total of 150 ft. of baseboards, multiplied by 600 will give you a total BTU of 90,000. Choose a boiler accordingly. For Furnace sizing, you must measure the air-space, or cubic volume, of your home. This is done by measuring all the room dimensions of the house, including hallways, closets, foyers and any other heated living area where vents are located. Multiply each area by the length, width, and height. If the ceiling height slopes in any room, such as 8 ft high in one side and slopes to 12 ft high on the other end, average the height. In this example, the average height would be 10 ft. After you have totaled all the air-space, multiply this figure by a factor of six. This will give you the total BTU output a furnace must produce. For instance, if your total of all the air-space in your home is 15,000, multiply by six and the total out you will need is 90,000 BTU furnace size. By Maury Jazzetti Website: http://www.betterlifestyles.com