HVAC & LOW CARBON HEATING
WHAT ARE THE BENEFITS OF DECENTRALISED VENTILATION?
Ian Thomas, product manager, TROX UK, examines how decentralised ventilation
can improve air quality while offering valuable energy efficiency advantages
O
ver the years, many buildings in the UK have been designed without air conditioning and
ventilation in mind. As the recent heatwaves have shown us, however, ignoring poor air quality is simply not an option. In addition to the complaints that occupants will inevitably make about stuffy, uncomfortable indoor spaces, the negative cognitive effects of inadequate air quality and inappropriate temperatures have been widely reported. In the absence of functioning air conditioning
systems, room occupants resort to their own solutions, such as standalone fans in summer or electric heaters in winter. These ad hoc attempts to improve occupant comfort can destroy any attempt to manage energy consumption, escalating utility bills and frustrating the sustainability attempts of those with responsibility for the environmental performance of the site. Buildings such as schools, offices, care homes and
gyms are often those at greatest risk, where the situation is exacerbated by comparatively high occupancy rates. Sometimes, however, the age and architectural features of the building are an issue. In heritage and listed buildings, for example, alterations to the fabric of the building, to accommodate traditional air conditioning systems, may simply not be acceptable or allowable. So how can you improve air quality in these types
of buildings if traditional air conditioning systems incorporating air handling units (AHUs) are not affordable, feasible or desirable?
OVERVIEW OF DECENTRALISED VENTILATION A key difference with this approach is that it does
not require the use of a central AHU, or connection to a building-wide ventilation system. The decentralised ventilation units deliver fresh air, heating, cooling, and heat recovery directly within the room - eliminating the need for long duct runs or central air handling plant. Unlike localised ventilation, driven from a central point, decentralised ventilation units are completely self-contained. Fresh air is delivered into the space by the unit, from the perimeter or fascia of the building, or from the ceiling void. Importantly, the units have integrated cross-flow
or rotary heat exchangers which prevent the heat from the room air being conducted outside without being used. Heat is recovered via the heat exchangers as the air passes through the units, providing free heating of the air in winter or free cooling in summer.
www.essmag.co.uk Units in the TROX range enable vertical or
horizontal installation next to windows, under window sills, directly under the ceiling or actually fitted into the suspended ceiling
ADVANTAGES Decentralised ventilation can deliver improvements
in air quality whilst also offering valuable energy efficiency advantages. • Improvements in air quality: Measurement of air quality is integrated into each ventilation unit. This means that the fresh air supply adapts automatically to demands, as usage and levels of occupancy of the room change throughout the day. In the TROX units, for example, an integrated sensor calculates air quality and adjusts the supply of fresh air to meet demand. The nominal airflow of the units is from 400 to 800m³/h, with a boost function (600 to 1100m³/h) offering
additional reserves which can be activated for temporary flushing of rooms during breaks.
• Energy efficiency: A key advantage of this technology is that heat recovery is available all year round, enabling heating from other sources to be reduced during the winter, and creating a cooler indoor environment in warmer weather. Best-in-class units employ rotary heat exchangers. In contrast to recuperative heat exchangers (where the airflows are separate and pass along numerous plates), the rotary heat exchangers operate regeneratively. The thermal energy is temporarily stored in the storage mass, a solid, slowly rotating wheel, and then, as the wheel comes into contact with the other airflow, is transferred to this other airflow. This process results in much higher efficiency levels.
SYSTEM DESIGN As each unit will require access to a fresh air
source, it is important to find a range of units offering as many configurations as possible, to ensure that they can be installed in many different physical locations, to suit the site. The TROX range, for example, includes units for vertical or horizontal installation next to windows, for placement under window sills of external walls, or for installation directly under the ceiling or actually fitted into the suspended ceiling. In summary, decentralised ventilation can
now provide a viable and affordable alternative where traditional air conditioning is not considered an option.
TROX
www.troxuk.co.uk
Air Quality Expert Group, Indoor Air Quality Report (2022) ‘
http://uk-air.defra.gov.uk/
ENERGY & SUSTAINABILITY SOLUTIONS - Autumn 2026 21
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