Editing Passive solar building design (section)

===Exterior colors reflecting – absorbing===
Materials and colors can be chosen to reflect or absorb [[solar thermal energy]]. Using information on a [[color]] for [[electromagnetic radiation]] to determine its [[thermal radiation]] properties of reflection or absorption can assist the choices.<ref>{{Cite web |url=http://www.energy.ca.gov/2006publications/CEC-500-2006-067/CEC-500-2006-067.PDF |title=Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory: Cool Colors |access-date=2008-01-15 |archive-date=2009-03-18 |archive-url=https://web.archive.org/web/20090318232120/http://www.energy.ca.gov/2006publications/CEC-500-2006-067/CEC-500-2006-067.PDF |url-status=dead }}</ref>

In cold climates with short winter days direct-gain systems utilizing equator-facing windows may actually perform better when snow covers the ground, since reflected as well as direct sunlight will enter the house and be captured as heat.{{Sfn|Kachadorian|2006|p=42,90}}