Building Energy Use Not Primed to Occupancy, MIT Says

by | Apr 9, 2012

MIT researchers have found that energy use does not always correspond to occupancy.

Their study, ENERNET: Studying the dynamic relationship between building occupancy and energy consumption, examining two MIT buildings, found that while electricity use corresponds to occupancy fairly well in those spaces, the activity of heating, ventilation and air conditioning (HVAC) systems in the buildings does not correlate closely to occupancy.

The paper examines two very different types of structures. Building 37 houses researchers in astrophysics, aeronautics and astronautics in a combination of offices, classrooms and labs, while building E52 is the home of MIT’s Department of Economics, comprising a sizable entrance atrium and a large number of offices. The researchers used the number of WiFi connections as a proxy for occupancy, a method they said could be replicated elsewhere at low cost.

As co-author Carlo Ratti noted, huge amounts of energy are often used to heat buildings up during the day – but buildings can empty out in just a few minutes. More dynamic energy use can therefore create huge savings.

The study, published in the April issue of the journal Energy and Buildings, suggests possible architectural or engineering solutions. For example, new sensing-based thermostats can control temperatures on a more precise level within buildings.

The report also suggest that existing spaces can be used for new purposes. For example, a once rarely used common space now hosts a snack bar, allowing its occupancy to more closely match the space’s energy use. Also, the researchers suggest that use of space within buildings could be planned to conserve energy, citing the example of high-occupancy offices positioned around a lecture hall, keeping the hall warmer.

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