How to Size a Modulating Boiler

Making your house more energy efficient involves looking both at the ways you use energy and the ways you waste it. One crucial aspect of this is choosing a new boiler for heating your home. Many people are selecting a modulating boiler that adjusts to the temperature in the home to reduce their energy usage. However, choosing the right one for your needs is key. Modulating boiler sizes are based on their kilowatt per hour output rather than their literal size.

Instructions

- 1
  Check your house to ensure it is properly insulated. You need to have the correct R-value in your walls, ceiling and windows for the climate you live in. The exact amount you need will depend on your location and the construction of your house.
- 2
  Calculate the cubic feet inside one of the rooms in your home. Multiply the result by the number of BTUs required per cubic foot in your climate heating zone. For example, Zone 5 locations like New York may need 40 to 45 BTUs per cubic foot, while warmer locations like North Carolina may only need 30 to 35.
- 3
  Subtract 10 percent for apartments or condos with heated neighbors, and 10 percent for sun-facing rooms. Add 10 percent for bathrooms or rooms with lots of windows.
- 4
  Repeat this process for all rooms. Total the results and add 10 percent for every 1,500 feet of elevation at your location to get the total BTUs required for the house.
- 5
  Multiply the number of BTUs by 0.000293071070172222. The result tells you the rating in kilowatts you need for your boiler.

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