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Title: Distribution and Room Air Mixing Risks to Retrofitted Homes

An energy efficiency upgrade reduces a home’s heating and cooling load. If the load reduction is great enough and the heating, ventilation, and air conditioning system warrants replacement, that system is often upgraded with a more efficient, lower capacity system that meets the load of the upgraded house. For a single-story house with floor supply air diffusers, the ducts often are removed and upgraded. For houses with ducts that are embedded in walls, the cost of demolition precludes the replacement of ducts. The challenge with the use of existing ducts is that the reduced airflow creates a decreased throw at the supply registers, and the supply air and room air do not mix well, leading to potential thermal comfort complaints. This project investigates this retrofit scenario. The issues and solutions discussed here are relevant to all climate zones, with emphasis on climates that require cooling. In this project, IBACOS performed load calculations for a two-story 1960s house and characterized duct sizes and layouts based on industry “rules of thumb” (Herk et al. 2014). The team performed duct-sizing calculations for unaltered ducts and post-retrofit airflows and examined airflow velocities and pressure changes with respect to various factors. The team then usedmore » a mocked-up duct and register setup to measure the characteristics of isothermal air—to reduce the effects of buoyancy from the observations—passing through the duct and leaving the register.« less
  1. IBACOS, Inc., Pittsburgh, PA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Technical Report
Research Org:
IBACOS, Inc., Pittsburgh, PA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Building Technologies Office (EE-5B). Building America Program
Contributing Orgs:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Country of Publication:
United States
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; RESIDENTIAL BUILDINGS; STRATIFICATION; COOLING; LEAKS; BUILDINGS residential; residential buildings; IBACOS; Building America; air distribution; stratification; throw; spread; cooling; pressure; leakage; register sizing; HVAC; buildings