Manual G Selection of Distribution Systems is a guide to selecting the most appropriate type of distribution system for a home or apartment building.

From the Preface
Selection of the best air distribution system is a critical step in achieving comfort air conditioning. The system must be selected from the standpoint of a number of factors; among them, the climatic zone, the type of structure, and conditions of occupancy. But proper selection of the system does not of itself automatically assure comfort air conditioning. A perimeter air-distribution system, for example, is an excellent choice for a structure in a northern climate, but this same system will prove completely unsatisfactory unless system components are selected and located to furnish proper air flow to the rooms.

Thus, after selection, the system must be designed to do the job for which it is intended and finally, it must be installed in accordance with the design. The subjects of design and installation are covered in Manual D and Manual T, respectively, of the Association series.

Early sections of this manual discuss factors which must be considered in system selection, and the last, Section 7, summarizes these factors in terms of a guide for selection. This is shown illustrated in Fig. 7.

This guide has been prepared by the Association staff in conjunction with members and upon consultation with manufacturers, contractors, and others actively engaged in the industry. Notice that three categories have been used in the guide:

RECOMMENDED A "recommended" air-distribution system is one which, in the opinion of the Association, will produce a high degree of comfort. The system which produces the highest degree of comfort, when properly designed and installed, will also be economical to install and operate and will therefore usually give the purchaser the best comfort value for his dollar. The term "recommended" must not be construed as denoting a deluxe system loaded with frills and accessories, or one which is otherwise a luxury system in any sense. Rather, the system is recommended because it will provide conditions which satisfy the basic comfort requirements for people occupying the home.

ACCEPTABLE The term "acceptable," as employed here, means the system is of a type which has been used for many years. It produces a degree of comfort which has been considered satisfactory - at least for those people who have not yet become accustomed to the degree of comfort which can be provided by systems classed as "recommended." When compared directly against a "recommended" system, the "acceptable" system will generally be found to produce a degree of comfort which can be classed only as "fair."

NOT ACCEPTABLE The term "not acceptable" means that, in the opinion of the Association, such a system does not provide an adequate degree of comfort. It may be deficient with regard to drafts, cold floors, large temperature gradients between floor and ceiling, or one or more other factors which adversely affect comfort. Occupants often try to overcome performance deficiencies by operating these systems in such a way that energy consumption and operating costs far exceed those for systems which produce better comfort conditions.

Table of Contents
Section 1: Factors Affecting Selection. Section 2: Types of Air Distribution Systems. Section 3: Local Climate. Section 4: Systems for Residences. Section 5: Systems for Apartments. Section 6: Special Considerations for Zoning. Section 7: Guide for System Selection.