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Energy Model Shows Economic Value of High-Performance HVAC
December 19, 2012
Today’s tip from Building Operating Management comes from Jeffrey L. Heiken of KlingStubbins: An energy model shows the value of high-performance HVAC systems.
An energy model is a design tool that goes beyond basic computer calculation needed to select equipment sizes. Many energy modeling software packages are available. The model electronically captures all design elements, from building skin to chiller selections, and simulates building operation. Information on occupancy and utilization, space temperature settings, lighting schedules, ventilation requirements, and utility rates all serve as inputs to the model. The software then uses solar and thermal weather data and predicts needs for the building in its specific location for each hour all year. The model produces load profiles and energy demands as well as operating cost for each utility in the simulation. The estimates from these energy models, though still estimates, have shown high levels of accuracy and, as input to life-cycle-cost analyses, serve very well for comparative analysis of systems and options.
Using the energy model, design of high-performance HVAC systems should start with the overarching goal of efficient resource use. The first step is to rightsize the delivery systems. Oversized equipment, piping, ducting, motors, pumps, chillers, air handlers, etc., can add significant operating and first costs. What’s more, there is the cost of added floor, shaft or plenum space for the HVAC system.
In the end equipment has to be selected. Unitary device energy efficiency ratings have improved, but how systems are set up can drive performance. Thus, high-performance HVAC systems also seek to maximize elements like economizer hours of operation, heat recovery and other elements such as thermal storage.
This has been a Building Operating Management Tip of the Day. Thanks for listening.