This work applies a new model that treats solar and longwave radiative transfer, thermal conduction, and sensible heat transport to quantify the flow of energy across single- and double-pane windows. A set of radiometers based in Chicago, Illinois, observed solar and longwave irradiances incident on and emerging from a window on a low-rise building. The incoming radiation fields, averaged over a 10-day period in January, drive the energy budget calculations, while a comparison of measured and computed outgoing irradiances validates the results. The indoor–outdoor temperature contrast creates a gradient in longwave radiative heating across the glass. This drives a heat flux that increases sensible heat flow to the exterior atmosphere by approximately a factor of 3 over what would exist without thermal radiation. Absorption of sunlight by the glass also increases energy lost to the atmosphere. For the conditions analyzed, approximately 40% of the solar energy absorbed by the window-plus-interior system is returned to the exterior as sensible heat and longwave radiation. The remaining absorbed solar energy offsets the demand for heating from the climate-control system.
Areas of Focus: Energy Markets
, Energy Efficiency
Well-functioning markets are essential for providing access to reliable, affordable energy. EPIC research is uncovering the policies, prices and information needed to help energy markets work efficiently.
Improving energy efficiency is lauded as a promising way reduce emissions and lower energy costs. Yet, a robust body of research demonstrates that not all efficiency investments deliver. EPIC faculty...