The Department of Energy’s (DOE’s) Lawrence Berkeley National Laboratory has completed studies on how walls, windows, roofs, lighting, equipment, and people impact the energy consumption of hvac equipment in residential and commercial buildings.

For homes, the studies found the largest contributor to cooling load is solar gain through the windows; the largest contributor to heating load is cold air seeping through windows and walls.

For commercial buildings, the greatest impact on cooling load comes from lighting and solar gain.

The full reports are available on the web at