Field comparison of design and diagnostic pathways for duct efficiency evaluation.

A new method of test for residential thermal distribution efficiency is currently being developed under the auspices of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). This test method will have three main approaches, or "pathways," designated Design, Diagnostic, and Research. The Design Pathway uses builder's information to predict thermal distribution efficiency in new construction. The Diagnostic Pathway uses air-flow, temperature, and pressure-difference tests-intended to take one to four hours-to evaluate thermal distribution efficiency in a completed house. For forced-air systems, three distinct techniques are being considered, one based on thermal inputs and outputs in the duct system, the second based on pressure and leakage-area measurements, and the third based on pressure differentials induced in the house by partial blockage of the return duct. This paper presents and discusses the results of Design Pathway calculations based on measured duct-system and floor-plan layouts and surface areas (in lieu of building plans) for fifteen residential duct systems in Long Island, New York. These are compared with measured Diagnostic Pathway efficiencies in eight of these homes.