Choosing Energy Effectiveness Rather than Efficiency
In order to be energy effective, it is important to look at the Life-Cycle Analysis (LCA) to see what lifecycle stage (material production, manufacturing, use, end-of-life) has the greatest environmental impact. It is important to focus efforts first on this stage before dedicating time to the others. Operational energy reduction is a key priority, since the most sustainable energy is energy saved. Energy itself is not of particular interest, but rather is a means towards desired ends. Clients desire the services that energy can deliver, for instance, comfort, illumination, power, transportation – not energy by itself. Hence, maximum energy efficiency with minimal environmental impact is the architectural challenge that ultimately allows us to “have our cake and eat it too”. In this context, material choices that impact operational energy are important, while they are less significant for the energy spent in manufacturing, construction and demolition of the building.
Therefore, two of the key objectives in designing sustainable buildings are to lower the operational energy consumption and the life-cycle costs of the building. This should be achieved by:
• First, focusing on improving the performance of the building envelope in order to lower the energy demand, as the life span of the envelope is between 50 and 100 years. Commonsense already tells us to focus on things such as air tightness of the building envelope, the quality of the insulation and especially of the windows, and to avoid thermal bridges.
• The second priority then should be to avoid energy use, for instance, by using efficient appliances and through the increased use and conversion of energy embedded in natural day-lighting (the ultraviolet and infra-red fractions).
• Once this has been accomplished, the focus should shift towards the generation of energy from ‘renewable’ source, as the life span of these systems is in the 10-25 years range. This approach is also dictated by simple economic considerations, as more capital is needed for an oversized renewable energy system to compensate for a poorly designed building envelope or for inefficient appliances.
In building, the most technically appropriate materials will lower operational energy costs over the life cycle of a building and demonstrate excellent durability. For example, composite materials involving carbon fibers or ceramic compounds may have a relatively high embodied energy, but when they are used appropriately, they can save energy in a building’s use-phase due to their advanced physical properties, e. g., insulation, strength, stiffness, heat or wear resistance.