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Back to basics for energy savings

Thermal destratification, the recy-cling of rising hot air, which has been described as the missing piece to the HVAC puzzle, is simple, effective and remarkably economical.

The only reason why this technique, which can offer savings on heating and cooling costs of between 20 and 50%, is not more widespread is that there is little awareness of how adaptable it is for use in virtually any space, with ceiling heights ranging from a normal office to supermarkets, showrooms, sports halls and high-bay warehouses.

Contrary to popular percep-tion, destratification is not the preserve of big spaces: if your ceiling is 2.5m high or more, you can benefit from destratification fans that are really no more complicated to install than a light fitting. The same simplicity applies even to a 38m aircraft hangar.

Most of us live and work in a space within two metres from the floor – any space above that is potentially a heat sink. Hot air rises, and then it has to be replaced to keep the working space at or near ground level within a comfortable, efficient working range – even more galling when you are actually generating heat as part of a production process or from computers or freezer cabinets, only to lose it to the roof space.

The higher the ceiling, the greater the heat gradient and potential heat loss. If you can recycle and re-use the heat that rises, then the savings are going to be immediate. Even a low ceilinged, insulated building can expect savings of 20 to 30% on space heating costs, and reductions of up to 50% are not unknown.

So what do you look for to get the comfort right and the savings maximised? The goal is to equalise the temperature throughout the space, minimising convective heat loss from the working area – in other words, to destratify the air space. The way to do this turns out to be remarkably simple, involving no complex programming of a building energy management system, no need for extra ACI units that need regular statutory inspections, or ductwork that will need cleaning and exhausting.

While some degree of destrati-fication can be achieved by simple paddle designs or basic box fans, designs that neutralise the turbulence that is created by the turning blades will enable significantly higher throughput in return for the same electrical input – up to 60% more. These designs will also “reach” right to the floor. The boosted throughput is achieved by special multi-blade stators, which neutralise the turbulence created by the fan blades. This means air is projected straight downwards in an even, predictable column, so gentle it will barely ruffle hair. The air spreads when it reaches resistance at the floor, quickly equalising heat distribution and eliminating hot and cold spots.

Stephen Bridges is managing director at Airius

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