Design and performance - closing the gap

There is a lot of discussion lately about the gap between the performance of buildings as designed and in use. There are any number of reasons that a building is not, for example, as energy efficient as it should be.

There can be errors made during design or construction of course. But perhaps the most significant impact on performance is the occupation of a building. Even the most brilliantly designed and built low-carbon office can see it’s energy use and emissions rise beyond predictions because of how people interact with it.

One solution could be to control all heating, lighting, cooling, ventilation centrally, minimising controls that can be ‘fiddled with’ by occupants. However, that approach has found to be ineffective – humans have a tendency to find ways to make the space their own including the use of under-desk heaters if they feel cold, or blocking ventilation grilles if they sense a draught.

Ignoring the need to control the work environment is therefore not a good idea. It is better to consider the needs of occupants carefully, assessing how much central control is appropriate, and what controls will work for occupants – not against them.

Modern controls are sometimes accused of being overly-complex, and it is occasionally the case that a system has been installed that is too complicated for the requirements of the end-user. Early involvement of and consultation with controls experts can help to avoid this.

In fact today’s controls technology is very flexible, allowing for provision of control which is just right for the building and its occupants. A happy balance can more readily be found between central control (with the emphasis on minimising energy use) and occupant control (allowing for greater personal comfort and productivity).

For example, use of controls that can be overridden but which return automatically to the original set-points offer localised comfort without the problems associated with leaving cooling ‘on’ when it’s not required.

The retrofitting of sensors  is made easier through wider application of wireless technology. For example, adding CO₂ sensors for meeting rooms will ensure that ventilation and cooling are applied when they are needed – before occupants become uncomfortable and turn up the cooling unnecessarily.

It is also important for designers to realise that occupants are more flexible that they are sometimes given credit for. Tightly specified temperatures can be unnecessary and waste energy. Allowing control parameters to be flexible by 2^oC to 3^oC can save significant amounts of energy.

Thinking more about occupants and how they react to the internal environment is key to closing the gap between design and performance. Controls are the link between humans and buildings and should be considered early in the design stage.