Editing Passive solar building design (section)

==Levels of application==

Many detached suburban houses can achieve reductions in heating expense without obvious changes to their appearance, comfort or usability.<ref>{{cite web|url=http://www.eere.energy.gov/de/passive_solar_design.html |title=Industrial Technologies Program: Industrial Distributed Energy |publisher=Eere.energy.gov |access-date=2010-03-16}}</ref> This is done using good siting and window positioning, small amounts of thermal mass, with good-but-conventional insulation, weatherization, and an occasional supplementary heat source, such as a central radiator connected to a (solar) water heater. Sunrays may fall on a wall during the daytime and raise the temperature of its [[thermal mass]]. This will then [[Thermal radiation|radiate]] heat into the building in the evening. External shading, or a radiant barrier plus air gap, may be used to reduce undesirable summer solar gain.

An extension of the "passive solar" approach to seasonal solar capture and storage of heat and cooling. These designs attempt to capture warm-season solar heat, and convey it to a [[Seasonal thermal energy storage|seasonal thermal store]] for use months later during the cold season ("annualised passive solar.") Increased storage is achieved by employing large amounts of thermal mass or [[Ground-coupled heat exchanger|earth coupling]]. Anecdotal reports suggest they can be effective but no formal study has been conducted to demonstrate their superiority. The approach also can move cooling into the warm season. Examples:

* [[Passive Annual Heat Storage]] (PAHS) – by John Hait
* [[Annualized Geothermal Solar]] (AGS) heating – by Don Stephen
* [[Earth sheltering|Earthed-roof]]

A "purely passive" solar-heated house would have no mechanical furnace unit, relying instead on energy captured from sunshine, only supplemented by "incidental" heat energy given off by lights, computers, and other task-specific appliances (such as those for cooking, entertainment, etc.), showering, people and pets. The use of natural convection air currents (rather than mechanical devices such as fans) to circulate air is related, though not strictly solar design. Passive solar building design sometimes uses limited electrical and mechanical controls to operate dampers, insulating shutters, shades, awnings, or reflectors. Some systems enlist small fans or solar-heated chimneys to improve convective air-flow. A reasonable way to analyse these systems is by measuring their [[coefficient of performance]]. A heat pump might use 1 J for every 4 J it delivers giving a COP of 4. A system that only uses a 30 W fan to more-evenly distribute 10&nbsp;kW of solar heat through an entire house would have a COP of 300.

Passive solar building design is often a foundational element of a cost-effective [[zero energy building]].<ref>{{cite web|url=http://www.nrel.gov/docs/fy06osti/39678.pdf |title=Cold-Climate Case Study for Affordable Zero Energy Homes: Preprint |access-date=2010-03-16}}</ref><ref>{{cite web |url=http://www.toolbase.org/PDF/CaseStudies/ZEHPrimer.pdf |archive-url=https://web.archive.org/web/20060813130840/http://www.toolbase.org/PDF/CaseStudies/ZEHPrimer.pdf |url-status=dead |archive-date=2006-08-13 |title=Zero Energy Homes: A Brief Primer |access-date=2010-03-16 }}</ref> Although a ZEB uses multiple passive solar building design concepts, a ZEB is usually not purely passive, having active mechanical renewable energy generation systems such as: [[wind turbine]], [[photovoltaics]], [[micro hydro]], [[Geothermal power|geothermal]], and other emerging alternative energy sources. Passive solar is also a core building design strategy for [[passive survivability]], along with other passive strategies.<ref>{{Cite web|url=https://www.buildinggreen.com/op-ed/passive-survivability|title=Passive Survivability|last=Wilson|first=Alex|date=1 December 2005|website=Building Green}}</ref>

===Passive solar design on skyscrapers===
There has been recent interest in the utilization of the large amounts of surface area on skyscrapers to improve their overall energy efficiency. Because skyscrapers are increasingly ubiquitous in urban environments, yet require large amounts of energy to operate, there is potential for large amounts of energy savings employing passive solar design techniques. One study,<ref>{{Cite journal|last=Lotfabadi|first=Pooya|title=Solar considerations in high-rise buildings|url=https://www.researchgate.net/publication/271226417|journal=Energy and Buildings|volume=89|pages=183–195|doi=10.1016/j.enbuild.2014.12.044|year=2015|bibcode=2015EneBu..89..183L }}</ref> which analyzed the proposed [[22 Bishopsgate]] tower in London, found that a 35% energy decrease in demand can theoretically be achieved through indirect solar gains, by rotating the building to achieve optimum ventilation and daylight penetration, usage of high thermal mass flooring material to decrease temperature fluctuation inside the building, and using double or triple glazed low emissivity window glass for direct solar gain. Indirect solar gain techniques included moderating wall heat flow by variations of wall thickness (from 20 to 30&nbsp;cm), using [[Glazing (window)|window glazing]] on the outdoor space to prevent heat loss, dedicating 15–20% of floor area for thermal storage, and implementing a [[Trombe wall]] to absorb heat entering the space. Overhangs are used to block direct sunlight in the summer, and allow it in the winter, and heat reflecting blinds are inserted between the thermal wall and the glazing to limit heat build-up in the summer months.

Another study<ref>{{Cite journal|last1=Wong|first1=Irene|last2=Baldwin|first2=Andrew N.|date=2016-02-15|title=Investigating the potential of applying vertical green walls to high-rise residential buildings for energy-saving in sub-tropical region|journal=Building and Environment|volume=97|pages=34–39|doi=10.1016/j.buildenv.2015.11.028|bibcode=2016BuEnv..97...34W |hdl=10397/44174|hdl-access=free}}</ref> analyzed double-green skin facade (DGSF) on the outside of high-rise buildings in Hong Kong. Such a green facade, or vegetation covering the outer walls, can combat the usage of air conditioning greatly - as much as 80%, as discovered by the researchers.

In more temperate climates, strategies such as glazing, adjustment of window-to-wall ratio, sun shading and roof strategies can offer considerable energy savings, in the 30% to 60% range.<ref>{{Cite journal|last1=Raji|first1=Babak|last2=Tenpierik|first2=Martin J.|last3=van den Dobbelsteen|first3=Andy|title=An assessment of energy-saving solutions for the envelope design of high-rise buildings in temperate climates: A case study in the Netherlands|journal=Energy and Buildings|volume=124|pages=210–221|doi=10.1016/j.enbuild.2015.10.049|year=2016|bibcode=2016EneBu.124..210R |url=http://resolver.tudelft.nl/uuid:cb563c4f-27ec-461e-ae1d-b2bc023a4843 }}</ref>