Underfloor air conditioning

Underfloor air conditioning can save space, materials and energy today, while future-proofing buildings for decades to come

By using the plenum beneath a raised floor as the ventilation zone instead of traditional ceiling-based air conditioning, it is possible to eliminate much of the ceiling-based duct and pipework, leading to huge savings in construction materials, installation costs, fit-out and reconfiguration costs. Building services traditionally consume a large proportion of a building’s operational energy use and construction practice often leads to wastage of materials and energy.

Removing the ceiling void in favour of underfloor air conditioning can result in a huge impact on the use of internal space within a building. Duplicating the floor void for cable management and ventilation lends itself to height savings in new build construction and refurbishments. The void or plenum beneath the raised access floor is usually in the region of 150-200mm, and a ceiling-based air conditioning system typically requires a void of 600-700mm, bringing the total services space requirement to 750-900mm.

By adopting an underfloor air conditioning system with floor level supply and floor level return, ceiling ductwork and lateral pipework can virtually be eliminated. A floor void of only 250-300mm is required to accommodate the cabling and fan terminals, equating to increased headroom of 200-400mm. Where the slab to slab height is severely restricted, a slimline fan terminal can be used, only requiring 180mm floor void space.

In new build construction, this saving can lead to additional lettable space or reduced building height; necessary in some cases to achieve planning permission. A tall building in Hong Kong adopted this system and was able to add an additional floor for every 10 floors constructed due to the height savings created. Transfer this across construction and there is potential to construct another whole building. Build 10 buildings, get one free! Undoubtedly attractive to any forward-thinking developer.

Plenum air conditioning can also maximise floor-to-ceiling height in refurbishment projects. In the UK, older building stock often has features such as limited headroom and smaller floorplates, making it a challenge for designers and engineers to accommodate the preferred 2.5m headroom using traditional ceiling-based air conditioning systems. Perimeter systems can be considered, but this brings the penalty of loss of prime lettable space and also makes it difficult to ventilate internal areas. Without a minimum floor-to-ceiling height of around 2.5m, agents are reluctant to promote commercial space as Grade A accommodation, a key aspect to corporate clients. Testament to this approach is the number of refurbished buildings that have adopted the underfloor air conditioning concept as a solution to slab-to-slab height restriction.

The height saving benefits of underfloor air conditioning systems are well proven, but that is not all. Minimising waste and energy consumption is achievable through using modular and flexible equipment that is easy to operate, clean, maintain and re-use. In this way, underfloor air conditioning systems can help architects, developers and clients future-proof their buildings for the next 20, 30 or 40 years.


Lucy Bonsall   

Marketing Manager

AET Flexible Space

Tel: +44 (0)1342 310400



Twitter: @AET_FSS

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