The new Manual J, 8th edition, procedures produce improved equipment sizing loads for single-family detached homes, small multi-unit structures, condominiums, town houses and manufactured homes. These procedures are also compatible with different types of comfort systems and applications such as:

• A central single-zone comfort system
• A central multi-zone system
• A distributed multi-zone system

• Homes with large south-facing glass area or rooms with unusually large glass area
• A thermally isolated solarium
• Customized internal load estimates

• Fenestration loads for glass rated by the National Fenestration Rating Council (NFRC)
• Improved duct load models
• Improved methods for estimation the effect of internal and external shading devices, including insect screens
• Infiltration estimated based on blower door test
• Sensitivity to latitude and altitude
• Sensitivity to skylight to roofing material, curb construction and light shaft construction
• Heat loss and gain for log walls, structural foam panels, aerated autoclaved concrete block, insulated form concrete panels, brick walls, concrete walls, wood foundation walls, and many other types of walls and insulation options

Part 1: Application of the Average Load Procedure is divided into four sections. Section 1: Loads provides load estimating procedures designed to produce an estimate of the heating and cooling loads that determine the size of single-zone and multizone equipment. Section 2: How to Use this Manual gives detailed instructions on the use of the manual. Section 3: Limited Application of the Average Load Procedure demonstrates the basic aspects of the average load procedure. It covers length, area, and volume calculations, the use of the weather data tables, design temperature difference calculations, the use of the tables that list multiplier values for fenestration and opaque panels, the equations used to estimate heating and cooling loads for generic fenestration and opaque panels, the default procedure used to estimate infiltration loads, the internal loads produced by people and appliances, the use of the duct load tables, the procedure used to estimate the ventilation loads and the procedures used to estimate ancillary loads. Section 4: General Application of the Average Load Procedure shows how to apply the average load procedure to a dwelling that has NFRC-rated fenestration and alternative types of wall construction. It also shows how to estimate heating load for floors that have radiant heat, and shows how to use the output from a blower door test or a component leakage area calculation to estimate infiltration rates and loads. Further, this section shows how to adjust the infiltration rate for pressurization or depressurization produced by a ventilation system, and also shows how ventilation loads are adjusted when heat-recovery equipment processes ventilation air.

Part 2: Components of the Average Load Procedure consists of Sections 5 through 14, as follows: Section 5: Design Conditions. Section 6: Fenestration Loads - Average Load Procedure provides two methods for computing heating and cooling loads for windows, glass doors, skylights and glass or plastic block windows. Section 7: Opaque Panel Loads - Average Load Procedure provides methods for computing the heating and cooling loads for above-grade walls, below-grade walls, partitions, ceilings, passive floors, floors equipped with radiant heating coils and doors. Section 8: Infiltration Loads describes three procedures used to estimate seasonal flow rates. Section 9: Internal Loads details internal loads, such as default appliance loads and occupancy loads. Section 10: Duct Loads. Section 11: Ventilation Loads. Section 12: Blower Heat. Section 13: Hot Water Piping Load presents information that can be used to estimate hot water piping loads. Section 14: Winter Humidification Load.

Part 3: Peak Load Procedure includes Sections 15 through 19, as follows: Section 15: Peak Cooling Load Procedure includes commentary, formulas, examples and tables to document the procedures used to estimate peak heat gains for individual rooms. Section 16: Peak Load Procedure for Dwelling with Inadequate Exposure Diversity demonstrates how to apply the peak load procedure to a dwelling that does not have adequate exposure diversity. Section 17: Dwelling with Adequate Exposure Diversity and a Multizone System demonstrates how to apply Manual J procedures to a dwelling that has adequate exposure diversity and a central multizone comfort system. Section 18: Homes with Large Glass Areas. Section 19: Solarium Heat Transfer Multipliers provides a method for converting fenestration performance data (assembly U-value, shading coefficient or solar heat gain coefficient) to heat transfer multipliers (HTM values). HTM tables for solarium glass and comments pertaining to system design are also included.

Manual J Appendices include Survey, Forms and Worksheets, Design Conditions, Fenestration, Opaque Panels, Infiltration, Ducts System Efficiency; Ventilation and Fresh Air, Hourly Cooling Load Factors for AED Calculations, Generic Fenestration Defaults, Glossary, and Users Guide - Electronic Workbook.