Heating, ventilation and air conditioning can represent a major part of a commercial building’s energy use. EECA estimates that HVAC accounts for around 40% of the typical energy bill of a New Zealand commercial building, making it one of the first areas worth examining when operating costs start to rise.
Reducing those costs does not necessarily mean replacing the entire system. Operating hours, temperature settings, maintenance, zoning and the condition of the building can all have a significant effect on how much energy HVAC equipment consumes.
Match HVAC Operating Hours to Occupancy
Heating or cooling an empty building wastes energy.
Check when the HVAC system starts and stops against the times the building is actually occupied. Systems are often left running because schedules have not been updated after changes to working hours, public holidays or daylight saving.
EECA estimates that optimising HVAC timing manually can reduce heating and cooling energy use by around 10–30%, depending on the building and existing controls. Building Management Systems can provide further opportunities by automatically managing schedules and equipment.
For commercial premises, check:
- weekday start and finish times
- weekend operation
- public holiday schedules
- areas occupied outside normal hours
- equipment running overnight unnecessarily
The goal is to condition the building when people need it, rather than simply leaving the system operating continuously.
Review Temperature Settings
Small changes to temperature settings can make a noticeable difference over hundreds or thousands of operating hours.
Excessive heating in winter and aggressive cooling in summer increase energy consumption without necessarily improving comfort.
EECA suggests considering heating to around 20°C and cooling from 24°C, rather than trying to maintain one temperature throughout the year. A gap between heating and cooling setpoints prevents the two modes from competing with each other. EECA estimates that a temperature band of at least 3°C can reduce heating and cooling energy use by approximately 2–10%.
Settings should still reflect the activities being carried out in the building and any specialist temperature requirements.
Use Zoning Properly
Commercial buildings rarely have identical heating and cooling requirements throughout.
A meeting room used for an hour has different requirements from an open-plan office occupied all day. Server rooms, kitchens, reception areas and rooms with large areas of glazing can also experience very different heat loads.
Commercial systems can use zoning to control different areas independently, helping avoid conditioning spaces that do not currently need it. Comfort Group notes that zoning and centralised controls are particularly valuable in commercial buildings because occupancy and internal heat loads vary significantly between areas.
Thermostats also need to be positioned correctly. Units located beside exterior doors, direct sunlight, heat-producing equipment or other unusual heat sources may give readings that do not represent the wider space. EECA recommends keeping thermostats away from these influences.
Keep Filters and Coils Clean
A commercial HVAC system has to move large volumes of air and transfer heat efficiently.
Dirty filters restrict airflow, while contaminated evaporator and condenser coils reduce heat-transfer performance. The system may still reach the required temperature, but it can take longer and use more energy doing it.
Regular servicing should include inspection and cleaning of filters, coils, heat exchangers and air outlets as required. EECA estimates that maintaining clean evaporator and condenser coils can reduce heating and cooling costs by approximately 5–15% in suitable systems.
Comfort Group recommends at least annual servicing as a practical baseline for commercial air conditioning, with more frequent maintenance appropriate for high-use, dusty or business-critical environments.
Check Ductwork for Air Leaks
In ducted systems, conditioned air needs to reach the occupied space.
Leaks can allow heated or cooled air to escape into ceiling cavities and other unconditioned areas before it reaches the room. Poor duct insulation can create additional losses.
EECA states that repairing gaps and leaks in ductwork can save approximately 1–5% of heating and cooling costs in applicable buildings.
Common areas to inspect include duct joints, flexible duct connections, insulation, dampers and connections around diffusers.
Reduce the Heating and Cooling Load
Improving HVAC efficiency is not only about the HVAC equipment.
The building itself determines how much heating and cooling is required. Solar gain through windows, draughts, damaged insulation and internal heat generated by computers or machinery can all increase the load.
EECA recommends measures such as using blinds to control unwanted solar heat, checking insulation, sealing unnecessary gaps and managing heat generated by servers, kitchens and other equipment.
Before increasing HVAC capacity, identify whether part of the problem can be removed at the source.
For example, extracting heat directly from a server or production area may be more efficient than continuously increasing cooling across the entire building.
Use Outside Air When Conditions Allow
Some commercial HVAC systems can use cooler outdoor air instead of relying entirely on mechanical refrigeration.
When outdoor conditions are suitable, increasing fresh-air intake can reduce the amount of mechanical cooling required. This is sometimes referred to as free cooling or an economiser strategy.
Whether it is practical depends on the HVAC design, outdoor conditions and the building’s ventilation requirements. Existing ventilation settings should not be changed without understanding how they affect indoor air quality and system performance. EECA identifies increased outdoor-air cooling as an efficiency opportunity where systems support it.
Use a Building Management System Effectively
A Building Management System, or BMS, can help larger facilities control HVAC based on schedules, zones and operating conditions.
Simply having a BMS installed does not guarantee lower energy use. Control strategies need to match how the building is actually occupied.
Useful functions can include:
- HVAC start and stop schedules
- individual zone control
- temperature monitoring
- holiday programming
- fault alerts
- energy monitoring
- automatic adjustment of equipment operation
EECA notes that a BMS can help businesses identify unnecessary operation and better control energy-using building services.
Energy monitoring also makes it easier to establish whether efficiency measures are producing real savings rather than relying on assumptions.
Make Sure the System Is Correctly Sized
A larger HVAC system is not automatically a better system.
Commercial air conditioning needs to be selected around the building’s actual load, including floor area, layout, occupancy, glazing, insulation, solar gain, equipment, ventilation requirements and operating hours.
Comfort Group identifies proper load assessment as the foundation of an efficient commercial HVAC system. Poor sizing and design can increase energy use, create inconsistent temperatures and place unnecessary strain on equipment.
Commercial requirements also vary considerably between buildings. A retail store, warehouse, office and hospitality venue cannot be treated as though they have identical HVAC demands.
Consider the Efficiency of Older Equipment
Maintenance can improve the performance of existing equipment, but there is a point where ageing HVAC systems become expensive to continue operating.
Modern systems can use inverter-driven compressors, variable refrigerant flow and more advanced controls to adjust output as demand changes rather than operating at full capacity unnecessarily. Comfort Group uses these technologies across commercial applications where appropriate.
An upgrade should still be assessed on overall operating cost rather than efficiency claims alone. Installation cost, remaining equipment life, maintenance requirements, building alterations and expected energy savings all need to be considered.
Current New Zealand Building Code provisions also include specific energy-efficiency requirements for commercial HVAC systems through Clause H1 and H1/VM3, covering areas including controls, fans, ductwork, pumps, air-conditioning equipment and energy monitoring.