Editing Solar energy (section)

===Heating, cooling and ventilation===
{{Main|Solar heating|Thermal mass|Solar chimney|Solar air conditioning}}
In the United States, [[HVAC|heating, ventilation and air conditioning]] (HVAC) systems account for 30% (4.65&nbsp;EJ/yr)<!--converted from 30% of 14.7 quads: 1.055 EJ/quad x 14.7 quad x 30%--> of the energy used in commercial buildings and nearly 50% (10.1&nbsp;EJ/yr)<!--source quotes residential HVAC energy usage of 10.1 EJ and total energy use of 20.3 EJ--> of the energy used in residential buildings.<ref>{{cite web|author=Apte, J.|display-authors=etal|title=Future Advanced Windows for Zero-Energy Homes|publisher=American Society of Heating, Refrigerating and Air-Conditioning Engineers|url=http://windows.lbl.gov/adv_Sys/ASHRAE%20Final%20Dynamic%20Windows.pdf|access-date=9 April 2008|url-status=dead|archive-url=https://web.archive.org/web/20080410212544/http://windows.lbl.gov/adv_Sys/ASHRAE%20Final%20Dynamic%20Windows.pdf|archive-date=10 April 2008}}</ref><ref>{{cite web|title=Energy Consumption Characteristics of Commercial Building HVAC Systems Volume III: Energy Savings Potential|publisher=United States Department of Energy|url=http://www.doas-radiant.psu.edu/DOE_report.pdf|access-date=24 June 2008}}</ref> Solar heating, cooling and ventilation technologies can be used to offset a portion of this energy.  Use of solar for heating can roughly be divided into [[Passive solar building design|passive solar]] concepts and [[Solar thermal energy|active solar]] concepts, depending on whether active elements such as [[solar tracker|sun tracking]] and solar concentrator optics are used.

[[File:Flipped MIT Solar One house.png|thumb|left|[[Massachusetts Institute of Technology|MIT]]'s Solar House #1, built in 1939 in the US, used [[seasonal thermal energy storage]] for year-round heating.]]
Thermal mass is any material that can be used to store heat—heat from the Sun in the case of solar energy. Common thermal mass materials include stone, cement, and water. Historically they have been used in arid climates or warm temperate regions to keep buildings cool by absorbing solar energy during the day and radiating stored heat to the cooler atmosphere at night. However, they can be used in cold temperate areas to maintain warmth as well. The size and placement of thermal mass depend on several factors such as climate, daylighting, and shading conditions. When duly incorporated, thermal mass maintains space temperatures in a comfortable range and reduces the need for auxiliary heating and cooling equipment.<ref>Mazria (1979), pp. 29–35</ref>

A [[solar chimney]] (or thermal chimney, in this context) is a passive solar ventilation system composed of a vertical shaft connecting the interior and exterior of a building. As the chimney warms, the air inside is heated, causing an [[updraft]] that pulls air through the building. Performance can be improved by using glazing and thermal mass materials<ref>{{cite news|last=Bright|first=David|date=18 February 1977|title=Passive solar heating simpler for the average owner|url=https://news.google.com/newspapers?id=beAzAAAAIBAJ&pg=1418,1115815&dq=improved+by+using+glazing+and+thermal+mass&hl=en|newspaper=Bangor Daily News|access-date=3 July 2011}}</ref> in a way that mimics greenhouses.

[[Deciduous]] trees and plants have been promoted as a means of controlling solar heating and cooling. When planted on the southern side of a building in the northern hemisphere or the northern side in the southern hemisphere, their leaves provide shade during the summer, while the bare limbs allow light to pass during the winter.<ref>Mazria (1979), p. 255</ref> Since bare, leafless trees shade 1/3 to 1/2 of incident solar radiation, there is a balance between the benefits of summer shading and the corresponding loss of winter heating.<ref>Balcomb (1992), p. 56</ref> In climates with significant heating loads, deciduous trees should not be planted on the Equator-facing side of a building because they will interfere with winter solar availability. They can, however, be used on the east and west sides to provide a degree of summer shading without appreciably affecting winter [[solar gain]].<ref>Balcomb (1992), p. 57</ref>