Proper Equipment & Duct Sizing

When someone refers to a ‘Manual J’, they are referring to a load calculation that follows the Air Conditioning Contractors of America (ACCA) procedure outlined in their Manual J. ’J’ stands for ‘joule’, which is a unit of measuring energy. A ‘load calculation’ is a calculation used to determine the maximum instantaneous heat that a furnace or boiler might need to provide for a building to maintain it’s nice cozy indoor air temperature of, say, 68 or 70 degrees Fahrenheit in the winter. Similar in the summer. By accounting for all of a building’s envelope surface areas and insulation values, as well as the building’s projected air infiltration rate, a heating or cooling load can be determined for a specific building in a specific location.


A Manual J calculation is oftentimes required by the local building jurisdiction prior to a new home construction to verify that the furnace or air conditioner is not going to be under-sized over-sized. Over-sizing can lead to some performance and efficiency problems, and can also induce excessive initial cost during construction.


If a building has a forced air heating or cooling system, then it will have a duct system to deliver that air to the building effectively. Duct systems are rarely designed and constructed properly. An effective duct design will utilize the ACCA Manual D procedure to determine size and airflow within the duct system.


Energy Innovations can provide you with a Manual D, also oftentimes required by the local building code prior to construction. We can also work with your architect and structural engineer to design a realistic duct layout (see blueprint) that can be used for bidding purposes, or ready to be used directly by the duct system installer.