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Energy efficiency can be achieved in a number of ways, but making improvements to HVAC systems can be one of the most significant.

Using large HVAC systems to control airflow and temperature requires a lot of energy per square metre. By implementing good HVAC system design, the carbon footprint can be dramatically reduced and air quality improved.

In a commercial building, ventilation requirements of a typical office is approximately four Air Changes per Hour (ACH). But greater demands on a HVAC system means more energy.

One way designers can improve energy efficiency is by reducing contaminant sources, as this lessens the required number of ACH. This can be done with behavioural changes and good operational practices.

The designer can then identify the right volumetric flow rates and create a low energy HVAC design.

Designers can also introduce Direct Digital Controls (DDC) to provide variable flow control for fume cupboards and supply air, depending on occupancy and usage.

Automatic occupancy controls can reduce the air change rates when there is reduced fume cupboard use, together with reduced overall flowrate during unoccupied periods, reducing energy usage of the HVAC system.

To further increase energy efficiency, designers can consider energy recovery technology, such as plate heat exchangers or run around coils. It may be necessary to protect these against chemicals, which can be done using stainless steel, vinyl coating or by using tinned coils.

Though additional fan energy is needed, low-pressure loss, high-efficiency heat exchanger design will improve the energy efficiency of the building.

As well as minimising the air change rate and energy recovery, the designer can reduce energy used by the extraction fan.

Traditional use of fresh air make-up, to maintain stack discharge velocity, can be more energy intensive than using a variable stack orifice or multi-stack discharge.

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