A few common sense but often overlooked principles can ensure energy savings and occupant satisfaction.
The in-use energy performance of too many buildings with green-design aspirations can disappoint, as recent studies continue to confirm. Are tighter codes the answer? Codes are supposed to be the minimum standard: LEED and other voluntary standards are supposed to demonstrate far better performance. Maybe it is not so much the codes but the practice that needs improving, so design intent takes better account of reality. From my experience in analyzing energy use and occupant satisfaction in dozens of buildings, I’ve got a few suggestions.
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First, people often confuse the energy used in buildings—everything that goes through the meters—with the energy used by buildings—the envelope, passive, and active systems that designers control. Hence they overestimate the savings achievable by design attention alone. For example, in a recent low-energy office, only 40 percent of its source energy use was under the direct control of the designer; the food service kitchen and server room accounted for the other 60 percent. Had the team realized this, they could have saved much more energy, and spent less money than they did on a large PV installation. We need to get much better at counting everything, linking expectations and outcomes, and installing effective submetering to show where energy is really going.
Second, buildings underperform due to slippage during design and construction, myopic “value” engineering, problems with construction quality and commissioning, and a lack of attention to detail. Here codes could bring some improvement by requiring that things be done better. In use, there is often unexpected wastage, for example, from a central plant operating inefficiently to meet small loads, lights, and equipment left on unnecessarily overnight, and little things nobody has thought about. We need to make sure that things are truly off when they are supposed to be off.
Third, complication is often the enemy of good performance, so we should aim to keep things simple and robust and to do them well. But legislation and voluntary programs often push us to add features in the name of sustainability, so there is yet more to go wrong. Computer modeling has a similar effect: Complicated solutions work well in the virtual world, but not in the real one. Many low-energy design strategies also rely on sophisticated electronic controls to match energy supply to demand and avoid waste. These controls don’t always work well and they are poorly understood by users and management, leading to dissatisfaction and wasted energy.
In reality, new and refurbished buildings are often used more intensively than their predecessors, so higher energy use doesn’t always represent inefficiency. We need better design assumptions and an increased understanding and reporting of occupancy patterns and how they affect energy use.
Most designers and builders are out of the picture as soon as their work is handed over. They seldom follow through into use, nor are they paid to do so. As a result, they don’t pass on their knowledge to the occupants, support fine tuning, and learn from the process. Usable Buildings Trust is developing a process called Soft Landings, which aims to make follow-through, post-occupancy evaluations, and feedback routine activities for design and building teams. Otherwise, the industry will continue to learn indirectly and too slowly for the challenges at hand.
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