How to Size a Boiler for Radiant Floor Heating

The federal Energy Star initiative follows the specific guidelines based upon the Air Conditioning Contractors of America's HVAC quality installation specification.
This nationally recognized industry standard lists as a number one priority correct sizing of the heating appliance to meet the home's need. You can use code compliance, fuel source selection and ACCA's Manual J 8AE Speed Sheet to correctly size a boiler for the residential environment. Refer to the References and Resources sections for these invaluable to tools to meet the Energy Star standards and correctly size a heating appliance.

Step 1

Choose a fuel source that is readily available and cost effective to install in the specific region where the boiler will be located. Since boilers are installed everywhere from Puerto Rico to Alaska and from Maine to Hawaii, the fuel source could be anything from coal, oil or natural gas to propane, wood or electricity. The fuel source determines the available brands, efficiencies, sizes and types of boilers that can be used. In some cases, you may have to install two small propane boilers instead of one large wood fired boiler.

Step 2

Determine the location for the installation, venting requirements and combustion air requirements mandated by the local and state authorities. If there are no codes governing the specific region, the International Mechanical Code gives a good foundation for a safe and workable installation. You must first source the codes enforced in the region where the boiler will be installed. For example, houses built in the slab-on-grade style will have heating appliances installed on the same level as the living space and usually use direct vent systems, whereas houses built with basements or cellars will have the heating appliance installed in a mechanical room in the basement and are usually vented in a chimney. Refer to the Resources for specific examples in the International Mechanical Code section for chimneys and vents.

Step 3

Watch the tutorial video for using the ACCA Speed Sheet in the Reference section and learn how to use the Speed Sheet properly to get an accurate calculation.

Step 4

Download the Speed Sheet in the Reference section.

Step 5

Gather and input all of the relevant applicable information for the given house where the boiler will be installed to complete the Manual J calculation.

About the Author

Nick Shipley began writing professionally for Demand Studios in 2010 in order to share his knowledge and experiences. Nick achieved his Master Licenses in plumbing, gas-fitting, heating, ventilation and air conditioning from the state of Maryland. He has over 10 years of experience working in the building and construction trades.