July 9, 2012, Brisbane, Australia
Sitting at the Healthy Buildings conference, I listened to Professor Jiang Yi´s talk about energy in buildings throughout the world. Professor Yi started talking about residential houses in the U.S. using air conditioning systems with fully closed windows in single family dwellings and commercial buildings. The survey showed that the power to control the indoor climate is the most important thing for occupants. Studies show that from 1950s to 1990s windows cannot be opened and use of ventilation systems with variable air volume (VAV) are primarily used in the U.S.
Very large differences have been found for same function buildings between different countries. Two projects, two campuses – one in Philadelphia and one in Beijing – show differences in operating hours, various amounts of energy for fans and methods of operating these fans, re-heating, etc. In one of his projects, he focused on why the demo buildings actually use more energy than conventional buildings with the same functions, i.e. 20 kWh/(m2.a) for electricity in demo buildings compared to approximately 5 kWh/(m2.a) in ordinary buildings? The results show that maintenance of10 air changes per hour at 24 h/day operation mode throughout the year, the specific building needs 140 kWh/(m2.a) for electricity energy; but if the operation mode is decreased to 16 hours per day, only half of the energy is needed.
These large differences in building energy are attributable to differences in lifestyle and patterns of building use. There are many factors that affect energy used in buildings, such as construction and materials, technical systems, outdoor climate, occupant activity, method of operation, set points and schedules, etc.
In Professors Yi´s speech, he said: „Can the Earth support the “Paradise”? If 7 billion people on Earth will live in the same way as today, 300 million people in the U.S. do, we would need 180% of current total world energy only to keep the buildings in operation.”
Professor Yi proposed to reduce energy in buildings using two types of low-energy buildings: 1. zero-energy buildings based on renewable resources with a number of high-techs or 2.changelifestyle along with the application of various usage modes and improving the indoor climate with suitable technologies.
Professor Yi concluded: “Whether a technology can save energy is highly dependent on the actual usage mode of buildings. There is a need for academic studies to study the occupant behavior, i.e. different cultures and classifications of typical occupant behavior.”
Photo by Petra Vladykova