Thermal destratification in buildings: The missing piece to the HVAC puzzle


Courtesy of Drumbeat Energy Limited

1. What is Thermal Destratification in buildings?
Over recent years there have been many products available to reduce energy in buildings such as LED lighting, efficient HVAC (heating, ventilation and air conditioning) systems, sub metering, variable speed drive units and improved building fabrics etc. The use of any or all of these options will reduce the carbon footprint of a building resulting in lower utility costs to the owner or occupier.

However, one of the fastest growing and most simple energy reduction initiatives which can be installed into both existing and new build facilities is THERMAL DESTRATIFICATION , rated by the Carbon Trust as one of the top carbon reducing initiatives for any type of building.

In all buildings the natural process of thermal stratification occurs, which can result in dramatic differences in temperature from floor to ceiling and wall to wall. Thermal stratification is caused by hot air rising up into the ceiling or roof space because it is lighter than the surrounding cooler air. The same applies to cool air falling to the floor as it is heavier than the surrounding warmer air. This means that HVAC systems have to constantly cycle on in order to maintain building interiors at a set and even temperature throughout.

HVAC systems are typically over delivering either heating or cooling to compensate for this stratification phenomenon in an attempt to achieve a required temperature at working/operating level, which is normally only around 1.5 metres to 2 metres from the floor. This costs a lot of money and creates a lot of carbon.

As a result large amounts of wasted heat can build up unseen in ceilings where the difference in temperature can easily rise 14° C or higher than the temperature at floor level depending on floor to ceiling height, and the higher the building the more extreme this temperature differential can be (Building Services Research and Information Association ). This heat is also increasing the Delta “T” between inside and outside, accelerating the rate at which hot air escapes through the roof.

This heat can easily be captured and reused by the installation of an efficient destratification fan system, which will balance internal temperatures and thus reduce the operation time and workload required of HVAC systems.

Mechanical engineers will argue that good HVAC design will ensure no stratification occurs within a space or building, however this is not the case as anyone who has worked in the roof space of a building will tell you. This can also be seen in the success of specific thermal destratification systems (such as the Airius system, ) across America, Australia, Europe and here in the United Kingdom.

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