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{{topic header|Passive water heater diagram 2 (2).jpg|Passive solar}}
{{topic header|Passive water heater diagram 2 (2).jpg|Passive solar}}
{{hatnote|Not to be confused with [[Passive House|PassivHaus / Passive House]] which is a performance-based energy standard in construction}}
[[File:Building-a-passive-solar-greenhouse.jpg|thumb|left|A passive solar [[greenhouse]].]]
'''Passive solar design''' is the harnessing or directing of solar energy through non-mechanical, non-electrical means. It is a key principle of [[green building]], often applied in designing buildings for maximum solar heating during cold winter months and maximum protection from the sun's heat during hot summer months.


'''Passive solar''' refers to the harnessing or directing of solar energy through non-mechanical, non-electrical means. It is often applied in designing buildings for maximum solar heating during cold winter months, and maximum protection from the sun's heat during hot summer months.
Passive solar is distinguished from active solar by the lack of operable devices.<ref name=thorpe2018 />


[[File:Building-a-passive-solar-greenhouse.jpg]]
==Passive solar vs Passive House==
The terms passive solar and passive house are often confused. The two terms refer to [[green building]] techniques and are closely related.<ref name=thorpe2018>Passive Solar Architecture Pocket Reference. D Thorpe. Earthscan from Routledge, 2018</ref>
 
Passive solar design is about making best use of available natural light and heat. Heat from the sun is collected (if heating is desired, i.e. in a cool climate). A major part of passive solar design is careful orientation with respect to the sun.<ref name=thorpe2018 />
 
Passive House design is about managing heat loss and heat gain (not just from the sun but from all sources). The intended result is to have a structure that requires minimal energy to heat and cool.<ref name=thorpe2018 /> 
 
As such, some state that passive house design has greater applicability than solar design since orientation with respect to the sun is not absolutely necessary. Passive House design does not necessarily require a structure which is elongated along the east-west axis with extensive glazing on the equator facing side. Indeed, the ideal form of a passive house is a cube (lower surface area to volume ratio).<ref name=thorpe2018 /> Passive solar houses are also said to be more complicated to design, and the internal temperature may fluctuate uncomfortably if they are designed poorly.<ref name=GBA2010>[https://www.greenbuildingadvisor.com/article/solar-versus-superinsulation-a-30-year-old-debate Solar Versus Superinsulation: A 30-Year-Old Debate]. Martin Holladay. Green Building Advisor, 2010</ref> Proponents of superinsulation state that compared to solar houses, greater savings can be obtained by building air tight with lots of insulation in walls and high R windows.<ref name=GBA2010 />
 
So, while some consider that the debate between passive solar and superinsulation resulted in the wider acceptance of superinsulation,<ref name=GBA2010 /> a more efficient approach would potentially be to utilise both passive solar and passive house design elements, which has been termed '''"Solar Passivhaus"'''.<ref name=thorpe2018 /> The remainder of this article therefore deals with passive solar in the modern sense of the term which is overlapping that of passive house design (rather than the original passive solar concepts in the 70s and 80s).
 
==Main types==
There are 6 main types of passive solar design.<ref name=Haggard>Passive Solar Architecture Pocket Reference. Ken Haggard, David A. Bainbridge, Rachel Aljilani. International Solar Energy Society / Routledge, 2016</ref> These can be considered in 3 generic categories in terms of the relationship between the thermal collector (or dissipator)and the interior space of the structure.<ref name=bainbridge2011>Passive Solar Architecture: Heating, Cooling, Ventilation, Daylighting and More Using Natural Flows. D Bainbridge, K Haggard. Chelsea Green Publishing, 2011</ref> There are 2 distinct approaches of each generic category.<ref name=bainbridge2011 />
 
===Direct gain===
Direct gain passive solar systems are where the thermal transfer occurs within the building interior.<ref name=bainbridge2011 /> Thermal mass may either be distrubeted throughout the building (e.g. the floors and the pole facing walls), or mass may be concentrated.<ref name=bainbridge2011 />
 
===Indirect gain===
In indirect gain systems, thermal transfer takes place at the building envelope.<ref name=bainbridge2011 /> The 2 types of indirect gain system are the thermal wall ([[Trombe wall]]) and the [[roof pond]].<ref name=bainbridge2011 />
 
===Isolated systems===
The 2 approaches of isolated systems are the sunspace and the [[thermosyphon]].<ref name=bainbridge2011 />
 
==Key design techniques==


Key [[building design]] techniques include:
Key [[building design]] techniques include:
* Planting [[deciduous trees]], or [[trellises]] covered in deciduous or annual [[vines]]. This may be as a fence or as a shade roof, and provides shade in summer, and light and warmth in summer.
*Planting [[deciduous trees]] or [[trellises]] covered in deciduous or annual [[vines]]. This may be as a fence or as a shade roof, and provides shade in summer and light and warmth in winter.
* Building components aligned to shade or welcome the sun according to its angle, e.g.
*Designing and building components with consideration for the seasonal change in the sun's position in the sky, and the influence this will have on the angle and intensity of light hitting the structure. Examples of this include:
** Broad [[eaves]]
**Broad [[eaves]], which block sunlight from entering windows during the summer, but allows it to enter during the winter when the sun is lower in the sky.
** Shade walls (less common). A wall or fence beyond the limits of the house, to provide shade. The wall runs east-west, on the east and/or west side of the house, and is on the north side of the house in the northern hemisphere, and on the south side in the southern hemisphere. (i.e. away from the equator). The angle and placement are calculated to shield from early morning or late afternoon sun in summer, but less so in winter. However this requires significant resources, and unless there are other reasons for a wall, it is generally better to use other methods, such as deciduous trees, or a f  especially where there are large windows)
**Shade walls (less common)
* [[Thermal mass]] (floor or thick walls)
***A wall or fence beyond the limits of the house, to provide shade. The wall runs east-west, on the east and/or west side of the house, and is on the north side of the house in the northern hemisphere, and on the south side in the southern hemisphere (i.e., away from the equator). The angle and placement are calculated to shield the house from early morning or late afternoon sun in summer but not in winter. However, this requires significant resources and, unless there are other reasons for a wall, it is generally better to use other methods, such as deciduous trees, or an awning, especially where there are large windows.
Thermal mass s a critical complement of any passive solar design. The purpose of it is to absorb or radiate heat energy. This has the effect of averaging out the extreme highs and lows are often accompanied by passive solar design.
*[[Thermal mass]] Thermal mass is a critical component of any passive solar design. Its purpose is to absorb and re-radiate heat energy. This has the effect of averaging out the daily extremes of high and low temperature. Thermal mass generally falls into two categories, passive and active. Passive thermal mass heat-storage systems include:
Thermal mass generally falls into two categories passive and active. In this case will talk about passive thermal mass storage systems.
**Thick masonry walls and floors
Some examples of pathos of thermal mass storage systems are:
**Phase-change materials
*Thick Masonry walls
***These materials change phase (typically from solid to liquid) when heated, storing a great deal of heat energy without a corresponding change in temperature.  Examples include various high-tech concrete additives and also natural resins, such as those found in Southern Yellow Pine.
*Thick Masonry floors
**Large liquid storage tanks inside the space to be heated (or cooled)
*Large liquids storage tanks stored inside the space to be heated (or cooled)
*Pipes to transfer heat between air and the thermal mass (e.g., in the ground under the house, either with natural convection or with a quiet low-power fan)
** Pipes to transfer heat between air and the thermal mass e.g. in the ground under the house, either with natural convection, or with a quiet low-power fan.
*[[White roofs]]
*[[White roofs]]
**Dark roofs absorb huge amounts of heat into buildings, especially when it's hot. This means more air conditioning is used to cool buildings, homes and workplaces become less comfortable, and those at risk of heat stress are in greater danger. Dark colors also radiate heat more easily in cold conditions, meaning greater heat loss from buildings and higher heating costs.  
**Dark roofs absorb large amounts of solar energy, which transfers into the building. This increase in absorbed heat requires increased electrical energy to remove and cool buildings, homes, and workplaces and maintain a comfortable environment. Dark colors also radiate heat more easily in cold conditions, meaning greater heat loss from buildings and higher heating costs.
**White surfaces have an increased albedo or "whiteness," which is the reflectivity of a surface. If a roof is more reflective less energy will be absorbed and transferred to the building.
*[[Solar closet]]s
**A shallow glass-fronted closet, lined with dark material, becomes very hot when exposed to the sun. One-way valves (which might be as simple as plastic sheet over wire mesh) allow cool air to enter at the bottom and hot air to exit at the top. They can be used for heating hot water, as well as for space heating.
*When these measures are appropriately utilized and combined the energy efficiency of a building can be much higher than with more conventional design measures.
 
==References==
{{reflist}}
== External links ==
 
* [http://www.ourcoolhouse.com/podcast/OurCoolHouse-Pasive_Solar_Design.mp3 Passive Solar Design] (MP3 audio file). Clear and basic explanation from the [http://www.ourcoolhouse.com/podcast/ OurCoolHouse Podcast]


{{Solar navbox}}
{{Solar navbox}}

Revision as of 09:12, 26 January 2019

A passive solar greenhouse.

Passive solar design is the harnessing or directing of solar energy through non-mechanical, non-electrical means. It is a key principle of green building, often applied in designing buildings for maximum solar heating during cold winter months and maximum protection from the sun's heat during hot summer months.

Passive solar is distinguished from active solar by the lack of operable devices.[1]

Passive solar vs Passive House

The terms passive solar and passive house are often confused. The two terms refer to green building techniques and are closely related.[1]

Passive solar design is about making best use of available natural light and heat. Heat from the sun is collected (if heating is desired, i.e. in a cool climate). A major part of passive solar design is careful orientation with respect to the sun.[1]

Passive House design is about managing heat loss and heat gain (not just from the sun but from all sources). The intended result is to have a structure that requires minimal energy to heat and cool.[1]

As such, some state that passive house design has greater applicability than solar design since orientation with respect to the sun is not absolutely necessary. Passive House design does not necessarily require a structure which is elongated along the east-west axis with extensive glazing on the equator facing side. Indeed, the ideal form of a passive house is a cube (lower surface area to volume ratio).[1] Passive solar houses are also said to be more complicated to design, and the internal temperature may fluctuate uncomfortably if they are designed poorly.[2] Proponents of superinsulation state that compared to solar houses, greater savings can be obtained by building air tight with lots of insulation in walls and high R windows.[2]

So, while some consider that the debate between passive solar and superinsulation resulted in the wider acceptance of superinsulation,[2] a more efficient approach would potentially be to utilise both passive solar and passive house design elements, which has been termed "Solar Passivhaus".[1] The remainder of this article therefore deals with passive solar in the modern sense of the term which is overlapping that of passive house design (rather than the original passive solar concepts in the 70s and 80s).

Main types

There are 6 main types of passive solar design.[3] These can be considered in 3 generic categories in terms of the relationship between the thermal collector (or dissipator)and the interior space of the structure.[4] There are 2 distinct approaches of each generic category.[4]

Direct gain

Direct gain passive solar systems are where the thermal transfer occurs within the building interior.[4] Thermal mass may either be distrubeted throughout the building (e.g. the floors and the pole facing walls), or mass may be concentrated.[4]

Indirect gain

In indirect gain systems, thermal transfer takes place at the building envelope.[4] The 2 types of indirect gain system are the thermal wall (Trombe wall) and the roof pond.[4]

Isolated systems

The 2 approaches of isolated systems are the sunspace and the thermosyphon.[4]

Key design techniques

Key building design techniques include:

  • Planting deciduous trees or trellises covered in deciduous or annual vines. This may be as a fence or as a shade roof, and provides shade in summer and light and warmth in winter.
  • Designing and building components with consideration for the seasonal change in the sun's position in the sky, and the influence this will have on the angle and intensity of light hitting the structure. Examples of this include:
    • Broad eaves, which block sunlight from entering windows during the summer, but allows it to enter during the winter when the sun is lower in the sky.
    • Shade walls (less common)
      • A wall or fence beyond the limits of the house, to provide shade. The wall runs east-west, on the east and/or west side of the house, and is on the north side of the house in the northern hemisphere, and on the south side in the southern hemisphere (i.e., away from the equator). The angle and placement are calculated to shield the house from early morning or late afternoon sun in summer but not in winter. However, this requires significant resources and, unless there are other reasons for a wall, it is generally better to use other methods, such as deciduous trees, or an awning, especially where there are large windows.
  • Thermal mass Thermal mass is a critical component of any passive solar design. Its purpose is to absorb and re-radiate heat energy. This has the effect of averaging out the daily extremes of high and low temperature. Thermal mass generally falls into two categories, passive and active. Passive thermal mass heat-storage systems include:
    • Thick masonry walls and floors
    • Phase-change materials
      • These materials change phase (typically from solid to liquid) when heated, storing a great deal of heat energy without a corresponding change in temperature. Examples include various high-tech concrete additives and also natural resins, such as those found in Southern Yellow Pine.
    • Large liquid storage tanks inside the space to be heated (or cooled)
  • Pipes to transfer heat between air and the thermal mass (e.g., in the ground under the house, either with natural convection or with a quiet low-power fan)
  • White roofs
    • Dark roofs absorb large amounts of solar energy, which transfers into the building. This increase in absorbed heat requires increased electrical energy to remove and cool buildings, homes, and workplaces and maintain a comfortable environment. Dark colors also radiate heat more easily in cold conditions, meaning greater heat loss from buildings and higher heating costs.
    • White surfaces have an increased albedo or "whiteness," which is the reflectivity of a surface. If a roof is more reflective less energy will be absorbed and transferred to the building.
  • Solar closets
    • A shallow glass-fronted closet, lined with dark material, becomes very hot when exposed to the sun. One-way valves (which might be as simple as plastic sheet over wire mesh) allow cool air to enter at the bottom and hot air to exit at the top. They can be used for heating hot water, as well as for space heating.
  • When these measures are appropriately utilized and combined the energy efficiency of a building can be much higher than with more conventional design measures.

References

Template:Reflist

External links

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Passive Solar Architecture Pocket Reference. D Thorpe. Earthscan from Routledge, 2018
  2. 2.0 2.1 2.2 Solar Versus Superinsulation: A 30-Year-Old Debate. Martin Holladay. Green Building Advisor, 2010
  3. Passive Solar Architecture Pocket Reference. Ken Haggard, David A. Bainbridge, Rachel Aljilani. International Solar Energy Society / Routledge, 2016
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Passive Solar Architecture: Heating, Cooling, Ventilation, Daylighting and More Using Natural Flows. D Bainbridge, K Haggard. Chelsea Green Publishing, 2011
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