Center for the Built Environment

Multi-zone variable air volume heating, ventilation, and air-conditioning systems are widely used in commercial buildings, but their performance varies significantly. Recent studies have found 4 to 15 percent variation in heating, ventilation, and air-conditioning energy consumption between different supply air temperature reset strategies in multi-zone variable air volume heating, ventilation, and air conditioning systems. Cost Optimized Reset is a dynamic, cost-responsive, supply-air-temperature set solution that minimizes heating, ventilation, and air conditioning cost by optimizing heating, cooling, and fan energy use. The objectives of this research demonstration project were to 1) refine the Cost Optimized Reset algorithm for wider adoption in commercial buildings in California, and 2) demonstrate the operation of Cost Optimized Reset in at least two buildings, evaluating energy and cost impacts.

The results indicated that Cost Optimized Reset, when compared to existing supply air temperature control strategies, can achieve 1 to 30 percent energy savings in a building with typical loads and airflows in Climate Zones 3 and 7; in some conditions, Cost Optimized Reset can achieve even higher savings. The results also indicated that simplified Cost Optimized Reset algorithms that use less data may achieve comparable performance, increasing the value of the strategy for a wide range of buildings.

Resolving these issues can yield substantial comfort and energy improvements, which are often required to effectively implement zone-demand-based reset methods. The team also identified the importance of supporting the implementers on Cost Optimized Reset deployment in buildings so that its intention is correctly interpreted and programmed.