ARLINGTON, Va. - The Air Conditioning Contractors of America (ACCA) has released a completely revised version of “Manual N,” the industry standard for calculating heat gain and heat loss for light commercial buildings.

According to the association, the new fifth edition of Manual N represents the first complete rewrite of the light commercial load calculation procedure in over two decades, addressing the many advances and changes in the construction industry that have taken shape, such as new materials, methods of assembly, and operational requirements.

Authored by Hank Rutkowski with the oversight of a committee comprised of representatives from across the HVACR industry, the fifth edition of Manual N provides instruction to help contractors and designers satisfy new (and often conflicting) energy, ventilation, and comfort requirements for light commercial buildings.

With enhanced procedures, capabilities, sensitivities, and applications, the new Manual N is divided into four sections, providing both a basic and comprehensive procedure for performing commercial load calculation:

Section 1, Abridged Procedure:Basic instructions to perform commercial load calculations, on buildings of three stories or less. Supports a simplified hand calculation.

Section 2, Advanced Topics:Provides enhanced procedures, capabilities, and sensitivities.

Section 3, Tables:Provides input for the worksheets and determinations needed for the abridged (N5ae) and full (N5) procedures.

Section 4, Appendices:Provides supporting materials and details on the N5ae and N5 applications.

The fifth edition of Manual N is now available for purchase at or by calling 888-290-2220. ACCA members save 25 percent off the list price.

A free spreadsheet program that can be used in conjunction with the abridged Manual N procedure has also been made available at

ACCA has scheduled two upcoming training classes in light commercial system design featuring the new Manual N, one in Florida and one in the Washington, D.C., area. For more information on training classes, visit

Publication date:02/25/2008