Tuning radiative heat flows between interior surfaces and human
occupants to improve heating and cooling efficiency
Abstract
Space heating and cooling in buildings account for nearly 20% of energy
use globally. In most buildings this energy is used to maintain the
thermal comfort of the building’s human occupants by maintaining the
interior air temperature at a particular set point. However, if one
could maintain the human occupant’s thermal comfort while decreasing the
heating or increasing the cooling set point, dramatic energy savings are
possible. Here, we propose and evaluate an untapped degree of freedom in
improving building efficiency: dynamically tuning the thermal emissivity
of interior building surfaces at long-wave infrared wavelengths to
maintain thermal comfort. We show that in cold weather conditions tuning
the emissivity of interior walls, floors and ceilings to a low value
(0.1) can decrease the set point temperature as much as 7°C,
corresponding to an energy saving of nearly 67.7% relative to high
emissivity materials (0.9). Conversely, in warm weather, high emissivity
interior surfaces result in a 38.5% energy savings relative to low
emissivity surfaces, highlighting the need for tunability for maximal
year-round efficiency. Our results reveal the remarkable energy savings
potential possible by better controlling the ubiquitous flows of heat
that surround us in the form of thermal radiation.