FANS
Optimising IEQ
Buildings located in busy, central areas can leave occupants exposed to pollution if they open the windows for ventilation. Chris Jones, product manager at Fläkt Woods, examines how mechanical ventilation units use demand-control fans and heat recovery devices to deliver clean air to building occupants while also minimising energy use.
I
n recognition of the need to consider the health and wellbeing of building occupants without compromising on energy effi ciency, a coalition of nine European HVAC and buildings bodies recently called for the European Parliament to improve Indoor Environment Quality (IEQ) as part of its review of the Energy Performance in Buildings Directive (EPBD).
IEQ includes indoor air quality, thermal comfort, lighting and acoustic environment experienced by building users, which the coalition argued are vital to citizens’ health, comfort and productivity.
The groups went on further to say that “Indoor Environment Quality can be enhanced through the use of mechanical ventilation and technical building systems which, when properly maintained, inspected and controlled will deliver positive outcomes.”
However, “the EPBD has so far been implemented with
insuffi cient consideration to IEQ.”
Solutions are already available on the market that can meet both the drive to improve IEQ and increase the energy effi ciency of commercial buildings.
For example, mechanical ventilation plays a key role in delivering optimum indoor air quality (IAQ) in buildings located in built-up areas.
High levels of noise and air pollution discourage occupants from opening windows for ventilation, which is a problem in
62 January 2018
the warmer months when ventilation is needed to prevent occupants from overheating. They may also be discouraged from opening windows in mid-season and winter months to avoid cold draughts.
In both circumstances, air handling units can deliver fresh air to people in the room, while simultaneously ensuring that indoor CO2
levels stay within those specifi ed by the
International WELL Building Institute guidelines. In order to ensure that energy consumption is minimised, speed controllable fans that match ventilation rates in accordance with the amount of people in the room at the time are usually incorporated into such a variable air volume (VAV) system.
These fans in a typical variable air volume system are normally linked to a CO2
and also the levels of CO2
sensor. As the number of occupants, increase, a signal is sent to the
frequency inverter, which changes the frequency of the electricity going to the fan, therefore increasing its speed. Vice versa, as people leave the building, the fans decrease in speed when there is less demand for fresh air. When an air handling unit is being commissioned, the engineer can set up the parameters which govern this process.
By varying the fan speed in the above manner, building operators can benefi t from the cube law principle in order to lower the extent of energy usage.
www.acr-news.com
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