EVALUATION OF VARIABLE VOLUME AND TEMPERATURE HVAC SYSTEM FOR COMMERCIAL AND RESIDENTIAL BUILDINGS

The variable volume and temperature (VVT) system meet energy efficienc y constraints during peak and partial load conditions while maintainin g thermal comfort requirements. Although there are numerous alternativ es available for changeover from an existing inefficient constant-air- volume system, the VVT system is of particular interest due to the fav orable economics and minimal time requirements for installation. The o bjectives of this paper are (1) the presentation of simulation results for constant-air-volume, variable-air-volume, and VVT systems; and (2 ) the comparison of annual energy consumption and economic selection f actors for these systems. A typical three-story office building and a typical residential building, located in Des Moines, Iowa, were examin ed. The results show that the VVT system should be considered during t he design stages for new projects and as a replacement in retrofit pro jects. For a commercial office building, the payback period for retrof it from a constant-air-volume system to the VVT system is estimated at 3-4 yr. For a residential building, capital-cost-recovery periods of 6 mo for retrofit and 18 mo for a new installation of the VVT system a re predicted.