Building as a System

Proper operational control of energy use is often a starting point for making cost-effective improvements and reducing carbon emissions. On the other hand it is also helpful to recognise a building as a dynamic system - with energy consumption influenced by its site and orientation, building envelop micro-climate, occupant behaviour, and landscaping and the surrounding vegetation. For example, ground soil and groundwater are both warmer in the winter and cooler in the summer than the ambient air temperature. Ground source pumps use these temperature differentials to pre-cool incoming air and reduce the energy requirement of air conditioners in summer, and do the reverse in winter.

Construction materials can play an important role, such as; masonry has a higher thermal mass than glass and steel, and therefore maintains a more even temperature. The lag time between heating and cooling can be used to maintain interior temperatures and reduce air conditioning loads.

Building occupants can be motivated to reduce internal heat gains in the summer by ensuring lights, computers, printers and other electrical equipment is turned off when not in use. Meanwhile staff can be encouraged not to overcool buildings simply because air conditioning is available. In fact it is better to encourage casual wear on hotter days to reduce cooling requirements.

Landscaping can provide a shade canopy in the summer, lock up carbon through photosynthesis, and reduce ambient temperatures through evapo-transpiration. Broad-leaf deciduous trees in particular have canopies which reduce passive solar gain in the summer while allowing it when needed in the winter.

This type of holistic view is easier for new-builds, where such considerations can be factored in at the planning stage. Options for cost-effective improvements are more limited with existing buildings. However, renovation does present real opportunities to improve the building envelope to manage heat flow. Natural ventilation can be improved by considering the placement of internal partition walls that do not impede cross ventilation, and windows can be retrofitted to make better use of night time cooling to lower cooling requirements during the day.