Heat recovery and demand control save energy in different ways. Heat recovery captures heat from exhaust air. Demand control reduces the volume of air handled when full air volume is not needed. The solutions can also be used together.
What does heat recovery do?
Heat recovery transfers heat from exhaust air to supply air. Less purchased energy is then needed to heat outdoor air.
Commercial kitchen exhaust air contains grease and other cooking contaminants. These must be considered in the design, cleaning, and maintenance of a heat recovery solution.
What does demand control do?
Demand control reduces air volume when the kitchen does not need full ventilation. Savings come from having less air to heat, cool, and move with fans.
Is demand control worthwhile if the site already has heat recovery?
It can be, and we can assess it free of charge. Heat recovery reduces the need for heating energy, but air volume, operating hours, and how ventilation is controlled still affect energy use.
It is also worth checking which kitchen exhaust air flows are connected to heat recovery. In many sites, for example, general exhaust and condensate hoods pass through heat recovery, but grease ducts do not.
FlowHero projects have been implemented profitably both at sites with heat recovery and at sites without a heat recovery system.
How do heat recovery and demand control projects differ?
Demand control is usually a lighter project. Adding heat recovery to an existing property can require changes to air handling units and ductwork and new duct routes to use recovered heat. Depending on the site, the project may also need building work, such as new roof structures.
Adding demand control is in practice a building automation project: sensors are installed in the kitchen to monitor use and air quality. Ventilation is then controlled automatically based on sensor data. Demand control can often be added to the current ventilation system without replacing air handling units, hoods, or ductwork. Ventilation sizing is not changed; air volume is controlled between the existing minimum and design values according to the kitchen’s needs.
Options should therefore be compared in terms of energy savings, investment, and required changes. If both make sense for the site, they can be used together.