Editing Passive solar building design (section)

===Convective heat transfer===
[[Convection (heat transfer)|Convective heat transfer]] can be beneficial or detrimental. Uncontrolled air infiltration from poor [[weatherization]] / weatherstripping / draft-proofing can contribute up to 40% of heat loss during winter;<ref>{{cite web |url=http://www.ornl.gov/sci/roofs+walls/whole_wall/airtight.html |title=BERC – Airtightness |publisher=Ornl.gov |date=2004-05-26 |access-date=2010-03-16 |archive-url=https://web.archive.org/web/20100828100447/http://www.ornl.gov/sci/roofs%2Bwalls/whole_wall/airtight.html |archive-date=2010-08-28 |url-status=dead }}</ref> however, strategic placement of operable windows or vents can enhance convection, cross-ventilation, and summer cooling when the outside air is of a comfortable temperature and [[relative humidity]].<ref>{{cite web|url=http://yourhome.gov.au/technical/fs46.html|title=Your Home Technical Manual - 4.6 Passive Cooling|date=20 March 2012|archive-url=https://web.archive.org/web/20120320202939/http://yourhome.gov.au/technical/fs46.html|archive-date=2012-03-20}}</ref> Filtered [[energy recovery ventilation]] systems may be useful to eliminate undesirable humidity, dust, pollen, and microorganisms in unfiltered ventilation air.

Natural convection causing [[stack effect|rising]] warm air and falling cooler air can result in an uneven stratification of heat. This may cause uncomfortable variations in temperature in the upper and lower conditioned space, serve as a method of venting hot air, or be designed in as a natural-convection air-flow loop for passive solar heat distribution and temperature equalization. Natural human cooling by [[perspiration]] and [[evaporation]] may be facilitated through natural or forced convective air movement by fans, but ceiling fans can disturb the stratified insulating air layers at the top of a room, and accelerate heat transfer from a hot attic, or through nearby windows. In addition, high [[relative humidity]] inhibits evaporative cooling by humans.