HOME

TheInfoList



In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute
solar energy Solar energy is Solar irradiance, radiant light and heat from the Sun that is harnessed using a range of technologies such as solar power to generate electricity, solar thermal energy including solar water heating, and solar architecture. It ...

solar energy
, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unlike active
solar heating A solar thermal collector collects heat by Absorption (optics), absorbing sunlight. The term "solar collector" commonly refers to a device for solar hot water panel, solar hot water heating, but may refer to large power generating installations s ...
systems, it does not involve the use of mechanical and electrical devices. The key to designing a passive solar building is to best take advantage of the local
climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...

climate
performing an accurate site analysis. Elements to be considered include window placement and size, and glazing type,
thermal insulation insulation, 1600 dpi scan Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulati ...

thermal insulation
,
thermal mass In building design, thermal mass is a property of the mass of a building which enables it to store heat, providing "inertia" against temperature fluctuations. It is sometimes known as the thermal flywheel effect. For example, when outside temperat ...
, and shading. Passive solar design techniques can be applied most easily to new buildings, but existing buildings can be adapted or "retrofitted".


Passive energy gain

upright=1.5, Elements of passive solar design, shown in a direct gain application ''Passive solar'' technologies use
sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible spectrum, visible, and ultraviolet light. On Earth, sunlight is light scattering by particles, scattered and attenuation, filtered thr ...

sunlight
without active mechanical systems (as contrasted to ''active solar'', which uses thermal collectors). Such technologies convert sunlight into usable heat (in water, air, and thermal mass), cause air-movement for
ventilating thumbnail, 250px, An ab anbar (water reservoir) with double domes and windcatchers (openings near the top of the towers) in the central desert city of Naeen, Iran. Windcatchers are a form of natural ventilation 250px, The ventilation system of a r ...
, or future use, with little use of other energy sources. A common example is a
solarium Solarium may refer to: * Sunroom, a room built largely of glass to afford exposure to the sun * A Terrace (building) or flat housetop * The ''Solarium Augusti'', a monumental meridian line (or perhaps a sundial) erected in Rome by Emperor Augustus ...

solarium
on the
equator The Earth's equator is an imaginary planetary line that is about long in circumference. The equator divides the planet into the Northern Hemisphere and Southern Hemisphere and is located at 0 degrees latitude In geography, latitude is ...

equator
-side of a building.
Passive cooling Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption. This approach works either by preventing heat from ...
is the use of similar design principles to reduce summer cooling requirements. Some passive systems use a small amount of conventional energy to control dampers, shutters, night insulation, and other devices that enhance solar energy collection, storage, and use, and reduce undesirable
heat transfer Heat transfer is a discipline of thermal engineering Thermal engineering is a specialized sub-discipline of mechanical engineering Mechanical engineering is an engineering Engineering is the use of scientific method, scientific prin ...

heat transfer
. Passive solar technologies include direct and indirect
solar gain 320px, Solar gain is illustrated by the snow on the roof of this house: sunlight has melted all of the snow, except for the area that is shaded by the chimney to the right. Solar gain (also known as solar heat gain or passive solar gain) is the i ...
for space heating,
solar water heating Solar water heating (SWH) is heating water by sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth Earth is the third planet from ...
systems based on the
thermosiphon Thermosiphon (or thermosyphon) is a method of passive heat exchange, based on natural convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and ...

thermosiphon
, use of
thermal mass In building design, thermal mass is a property of the mass of a building which enables it to store heat, providing "inertia" against temperature fluctuations. It is sometimes known as the thermal flywheel effect. For example, when outside temperat ...
and
phase-change materials A sodium acetate heating pad. When the sodium acetate solution crystallises, it becomes warm.">heating_pad.html" ;"title="sodium acetate heating pad">sodium acetate heating pad. When the sodium acetate solution crystallises, it becomes warm. A ph ...
for slowing indoor air temperature swings,
solar cooker
solar cooker
s, the
solar chimney:''This article refers to a device for ventilation. For the power generation technology, see Solar updraft tower.'' A solar chimney often referred to as a thermal chimney is a way of improving the natural ventilation of buildings by using convecti ...

solar chimney
for enhancing natural ventilation, and
earth sheltering An earth shelter is a structure (usually a house A house is a single-unit residential building, which may range in complexity from a rudimentary hut to a complex structure of wood, masonry, concrete or other material, outfitted with plumbing, ...

earth sheltering
. More widely, solar technologies include the
solar furnace A solar furnace is a structure that uses concentrated solar power to produce high temperatures, usually for industry. Parabolic mirrors or heliostats concentrate light (Insolation) onto a focus (optics), focal point. The temperature at the focal ...
, but this typically requires some external energy for aligning their concentrating mirrors or receivers, and historically have not proven to be practical or cost effective for widespread use. 'Low-grade' energy needs, such as space and water heating, have proven over time to be better applications for passive use of solar energy.


As a science

The
scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe."... modern science is a discovery as well as an invention. ...

scientific
basis for passive solar building design has been developed from a combination of
climatology Climatology (from Greek , ''klima'', "place, zone"; and , '' -logia'') or climate science is the scientific study of climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is th ...
,
thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by ...

thermodynamics
(particularly
heat transfer Heat transfer is a discipline of thermal engineering Thermal engineering is a specialized sub-discipline of mechanical engineering Mechanical engineering is an engineering Engineering is the use of scientific method, scientific prin ...

heat transfer
:
conduction (heat) Thermal conduction is the transfer of internal energy by microscopic collisions of particles and movement of electrons within a body. The colliding particles, which include molecules, atoms and electrons, transfer disorganized microscopic kinetic a ...
,
convection Convection is single or multiphase fluid flow In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including ''aerodynamic ...

convection
, and
electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. ...

electromagnetic radiation
),
fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned with the motions of physical objects, more specifically the relationships among force, matter, and moti ...
/
natural convection . Natural convection is a type of flow, of motion of a liquid such as water or a gas such as air, in which the fluid motion is not generated by any external source (like a pump, fan, suction device, etc.) but by some parts of the fluid being heavie ...
(passive movement of air and water without the use of electricity, fans or pumps), and human
thermal comfort Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation ( ANSI/ASHRAE Standard 55).ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupanc ...
based on heat index,
psychrometrics Psychrometrics, psychrometry, and hygrometry are names for the field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures. The term comes from the Greek ''psuchron'' (ψυχρόν) meaning "cold" and ''metr ...
and
enthalpy Enthalpy , a property of a thermodynamic system, is the sum of the system's internal energy and the product of its pressure and volume. It is a state function used in many measurements in chemical, biological, and physical systems at a constant pr ...

enthalpy
control for buildings to be inhabited by humans or animals,
sunroom A sunroom, also frequently called a solarium (and sometimes a "Florida room", "garden conservatory", "garden room", "patio room", "sun parlor", "sun porch", "three season room" or "winter garden"), is a room that permits abundant daylight and vie ...
s, solariums, and
greenhouse '' (giant Amazon waterlilies) in a large greenhouse at the Saint Petersburg Botanical Garden. A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of transparent mater ...

greenhouse
s for raising plants. Specific attention is divided into: the site, location and solar orientation of the building, local
sun path 300px, Sun path polar chart for any location at the latitude of Rotterdam Sun path, sometimes also called day arc, refers to the daily Daily or The Daily may refer to: Journalism * Daily newspaper A newspaper is a Periodical lit ...
, the prevailing level of
insolation Solar irradiance is the power (physics), power per unit area received from the Sun in the form of electromagnetic radiation as measured in the wavelength range of the measuring instrument. The solar irradiance is measured in watt per square metr ...

insolation
(
latitude In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets. The first person to use the w ...

latitude
/sunshine/clouds/
precipitation In meteorology Meteorology is a branch of the atmospheric sciences Atmospheric science is the study of the Earth's atmosphere File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. L ...
), design and construction quality/materials, placement/size/type of windows and walls, and incorporation of solar-energy-storing
thermal mass In building design, thermal mass is a property of the mass of a building which enables it to store heat, providing "inertia" against temperature fluctuations. It is sometimes known as the thermal flywheel effect. For example, when outside temperat ...
with
heat capacity Heat capacity or thermal capacity is a physical property A physical property is any property Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. Depending on t ...
. While these considerations may be directed toward any building, achieving an ideal optimized cost/performance solution requires careful,
holistic Holism (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as ...
,
system integration System integration is defined in engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The disc ...
engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...

engineering
of these scientific principles. Modern refinements through computer modeling (such as the comprehensive U.S. Department of Energy "Energy Plus" building energy simulation software), and application of decades of lessons learned (since the 1970s energy crisis) can achieve significant energy savings and reduction of environmental damage, without sacrificing functionality or aesthetics. In fact, passive-solar design features such as a greenhouse/sunroom/solarium can greatly enhance the livability, daylight, views, and value of a home, at a low cost per unit of space. Much has been learned about passive solar building design since the 1970s energy crisis. Many unscientific, intuition-based expensive construction experiments have attempted and failed to achieve zero energy – the total elimination of heating-and-cooling energy bills. Passive solar building construction may not be difficult or expensive (using off-the-shelf existing materials and technology), but the scientific passive solar building design is a non-trivial engineering effort that requires significant study of previous counter-intuitive lessons learned, and time to enter, evaluate, and iteratively refine the
simulation A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of Conceptual model, models; the model represents the key characteristics or behaviors of the selected system or process, wh ...
input and output. One of the most useful post-construction evaluation tools has been the use of
thermography Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a Thermographic camera, thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are e ...
using digital
thermal imaging cameras
thermal imaging cameras
for a formal quantitative scientific
energy audit An energy audit is an inspection survey and an analysis of energy In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science ...
. Thermal imaging can be used to document areas of poor thermal performance such as the negative thermal impact of roof-angled glass or a skylight on a cold winter night or hot summer day. The scientific lessons learned over the last three decades have been captured in sophisticated comprehensive building energy simulation computer software systems (like U.S. DOE Energy Plus). Scientific passive solar building design with quantitative cost benefit product optimization is not easy for a novice. The level of complexity has resulted in ongoing bad-architecture, and many intuition-based, unscientific construction experiments that disappoint their designers and waste a significant portion of their construction budget on inappropriate ideas. The economic motivation for scientific design and engineering is significant. If it had been applied comprehensively to new building construction beginning in 1980 (based on 1970s lessons learned), America could be saving over $250,000,000 per year on expensive energy and related pollution today. Since 1979, Passive Solar Building Design has been a critical element of achieving zero energy by educational institution experiments, and governments around the world, including the U.S. Department of Energy, and the energy research scientists that they have supported for decades. The
cost effective Cost-effectiveness analysis (CEA) is a form of economic financial analysis, analysis that compares the relative costs and outcomes (effects) of different courses of action. Cost-effectiveness analysis is distinct from cost–benefit analysis, which ...
proof of concept Proof of concept (PoC), also known as proof of principle, is a realization of a certain method or idea in order to demonstrate its feasibility study, feasibility, or a demonstration in principle with the aim of verifying that some concept or theor ...
was established decades ago, but
cultural changeCulture change is a term used in public policy making that emphasizes the influence of cultural capital on individual and community behavior. It has been sometimes called repositioning of culture, which means the reconstruction of the cultural concep ...
in architecture, the construction trades, and building-owner
decision making In psychology Psychology is the science of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, as well as feeling and thought. It is an academic discipline of immense s ...

decision making
has been very slow and difficult. The new terms "Architectural Science" and "Architectural Technology" are being added to some schools of Architecture, with a future goal of teaching the above scientific and energy-engineering principles.


The solar path in passive design

The ability to achieve these goals simultaneously is fundamentally dependent on the seasonal variations in the sun's path throughout the day. This occurs as a result of the
inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object. ...

inclination
of the Earth's axis of rotation in relation to its
orbit In celestial mechanics, an orbit is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificial satellite around an object or pos ...

orbit
. The
sun path 300px, Sun path polar chart for any location at the latitude of Rotterdam Sun path, sometimes also called day arc, refers to the daily Daily or The Daily may refer to: Journalism * Daily newspaper A newspaper is a Periodical lit ...
is unique for any given latitude. In Northern Hemisphere non-tropical latitudes farther than 23.5 degrees from the equator: * The sun will reach its
highest point A list of highest points typically contains the name, elevation, and location of the highest point in each of a set of geographical regions. Such a list is important in the sport of highpointing Highpointing is the sport of ascending to the point ...

highest point
toward the south (in the direction of the equator) * As winter
solstice A solstice is an event that occurs when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere In astronomy and navigation, the celestial sphere is an abstraction, abstr ...

solstice
approaches, the
angle In Euclidean geometry, an angle is the figure formed by two Ray (geometry), rays, called the ''sides'' of the angle, sharing a common endpoint, called the ''vertex (geometry), vertex'' of the angle. Angles formed by two rays lie in the plane (ge ...

angle
at which the sun and progressively moves further toward the South and the daylight hours will become shorter * The opposite is noted in summer where the sun will rise and set further toward the North and the daylight hours will lengthen The converse is observed in the Southern Hemisphere, but the sun rises to the east and sets toward the west regardless of which hemisphere you are in. In equatorial regions at less than 23.5 degrees, the position of the sun at
solar noon Noon (or midday) is 12 o'clock The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic bran ...

solar noon
will oscillate from north to south and back again during the year. In regions closer than 23.5 degrees from either north-or-south pole, during summer the sun will trace a complete circle in the sky without setting whilst it will never appear above the horizon six months later, during the height of winter. The 47-degree difference in the altitude of the sun at
solar noon Noon (or midday) is 12 o'clock The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic bran ...
between winter and summer forms the basis of passive solar design. This information is combined with local climatic data (
degree day A degree day is a measure of heat In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter. The various mechanisms of energy transfer that define ...
) heating and cooling requirements to determine at what time of the year solar gain will be beneficial for
thermal comfort Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation ( ANSI/ASHRAE Standard 55).ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupanc ...
, and when it should be blocked with shading. By strategic placement of items such as glazing and shading devices, the percent of solar gain entering a building can be controlled throughout the year. One
passive solar In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unlike ...
sun path design problem is that although the sun is in the same relative position six weeks before, and six weeks after, the solstice, due to "thermal lag" from the
thermal mass In building design, thermal mass is a property of the mass of a building which enables it to store heat, providing "inertia" against temperature fluctuations. It is sometimes known as the thermal flywheel effect. For example, when outside temperat ...
of the Earth, the temperature and solar gain requirements are quite different before and after the summer or winter solstice. Movable shutters, shades, shade screens, or window quilts can accommodate day-to-day and hour-to-hour solar gain and insulation requirements. Careful arrangement of rooms completes the passive solar design. A common recommendation for residential dwellings is to place living areas facing solar noon and sleeping quarters on the opposite side. A heliodon is a traditional movable light device used by architects and designers to help model sun path effects. In modern times, 3D computer graphics can visually simulate this data, and calculate performance predictions.


Passive solar heat transfer principles

Personal
thermal comfort Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation ( ANSI/ASHRAE Standard 55).ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupanc ...
is a function of personal health factors (medical, psychological, sociological and situational), ambient air temperature,
mean radiant temperature__NOTOC__ The mean radiant temperature (MRT) is defined as the uniform temperature of an imaginary enclosure in which the radiant heat transfer from the human body The human body is the structure of a human being. It is composed of many differe ...
, air movement (
wind chill A chart of wind chill values for given air temperatures and wind speeds Wind-chill or windchill (popularly wind chill factor) is the lowering of body temperature due to the passing-flow of lower-temperature air. Wind chill numbers are always low ...

wind chill
,
turbulence In fluid dynamics In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including aerodynamics (the study of air and other gases ...
) and
relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog to be ...

relative humidity
(affecting human cooling).
Heat transfer Heat transfer is a discipline of thermal engineering Thermal engineering is a specialized sub-discipline of mechanical engineering Mechanical engineering is an engineering Engineering is the use of scientific method, scientific prin ...

Heat transfer
in buildings occurs through
convection Convection is single or multiphase fluid flow In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including ''aerodynamic ...

convection
, , and
thermal radiation Thermal radiation in visible light can be seen on this hot metalwork. Its emission in the infrared is invisible to the human eye. Infrared cameras are capable of capturing this infrared emission (see Thermography). Thermal radiation is electrom ...
through roof, walls, floor and windows.


Convective heat transfer

Convective heat transfer can be beneficial or detrimental. Uncontrolled air infiltration from poor
weatherization Weatherization (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American En ...
/ weatherstripping / draft-proofing can contribute up to 40% of heat loss during winter; 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 Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog to be ...

relative humidity
. Filtered
energy recovery ventilation Energy recovery ventilation (ERV) is the energy recovery Energy recovery includes any technique or method of minimizing the input of energy to an overall system by the energy transfer, exchange of energy from one sub-system of the overall system ...
systems may be useful to eliminate undesirable humidity, dust, pollen, and microorganisms in unfiltered ventilation air. Natural convection causing
rising Rising may refer to: * Rising, a stage in baking - see Proofing (baking technique) *Elevation * Short for Uprising, a rebellion Film and TV * Rising (Stargate Atlantis), "Rising" (''Stargate Atlantis''), the series premiere of the science fiction t ...
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 In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unlike ...
heat distribution and temperature equalization. Natural human cooling by
perspiration Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protecti ...
and
evaporation File:10. Ладење при испарување.ogv, 280px, Demonstration of evaporative cooling. When the sensor is dipped in ethanol and then taken out to evaporate, the instrument shows progressively lower temperature as the ethanol evapor ...

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 Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog to be ...

relative humidity
inhibits evaporative cooling by humans.


Radiative heat transfer

The main source of
heat transfer Heat transfer is a discipline of thermal engineering Thermal engineering is a specialized sub-discipline of mechanical engineering Mechanical engineering is an engineering Engineering is the use of scientific method, scientific prin ...

heat transfer
is
radiant energy In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Ph ...
, and the primary source is the sun. Solar radiation occurs predominantly through the roof and windows (but also through walls).
Thermal radiation Thermal radiation in visible light can be seen on this hot metalwork. Its emission in the infrared is invisible to the human eye. Infrared cameras are capable of capturing this infrared emission (see Thermography). Thermal radiation is electrom ...
moves from a warmer surface to a cooler one. Roofs receive the majority of the solar radiation delivered to a house. A
cool roofImage:Roof-albedo.gif, 300px, The albedo of several types of roofs Reflective surfaces can deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to the surface) an ...
, or
green roof A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a Waterproofing#Construction waterproofing, waterproofing membrane. It may also include additional lay ...

green roof
in addition to a
radiant barrier A radiant barrier is a type of building material that reflects thermal radiation and reduces heat transfer. Because thermal energy is also transferred by Conduction (heat), conduction and convection, in addition radiation, radiant barriers are of ...
can help prevent your attic from becoming hotter than the peak summer outdoor air temperature (see
albedo Albedo (prounounced ; la, albedo, meaning 'whiteness') is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiat ...

albedo
, absorptivity,
emissivity work iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is ...
, and
reflectivity The reflectance of the surface of a material is its effectiveness in reflecting radiant energy In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , ...
). Windows are a ready and predictable site for
thermal radiation Thermal radiation in visible light can be seen on this hot metalwork. Its emission in the infrared is invisible to the human eye. Infrared cameras are capable of capturing this infrared emission (see Thermography). Thermal radiation is electrom ...
. Energy from radiation can move into a window in the day time, and out of the same window at night. Radiation uses
photon The photon ( el, φῶς, phōs, light) is a type of elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be eleme ...

photon
s to transmit
electromagnetic waves In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through ...

electromagnetic waves
through a vacuum, or translucent medium. Solar heat gain can be significant even on cold clear days. Solar heat gain through windows can be reduced by
insulated glazing File:EURO 68 wooden window profile with insulated glazing 02.JPG, EURO 68 wooden window profile with insulated glazing Insulating glass (IG) consists of two or more glass Paned window (architecture), window panes separated by a space to reduce he ...
, shading, and orientation. Windows are particularly difficult to insulate compared to roof and walls. Convective heat transfer through and around
window covering Window coverings are considered any type of materials used to cover a window A window is an opening in a wall, door, roof, or vehicle that allows the passage of light and may also allow the passage of sound and sometimes air. Modern windows ar ...
s also degrade its insulation properties. When shading windows, external shading is more effective at reducing heat gain than internal
window covering Window coverings are considered any type of materials used to cover a window A window is an opening in a wall, door, roof, or vehicle that allows the passage of light and may also allow the passage of sound and sometimes air. Modern windows ar ...
s. Western and eastern sun can provide warmth and lighting, but are vulnerable to overheating in summer if not shaded. In contrast, the low midday sun readily admits light and warmth during the winter, but can be easily shaded with appropriate length overhangs or angled louvres during summer and leaf bearing summer shade trees which shed their leaves in the fall. The amount of radiant heat received is related to the location
latitude In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets. The first person to use the w ...

latitude
,
altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum Data are units of information Information can be thought of as the resolution of unce ...

altitude
,
cloud cover Cloud cover (also known as cloudiness, cloudage, or cloud amount) refers to the fraction of the sky obscured by cloud In meteorology Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmosph ...
, and seasonal / hourly angle of incidence (see
Sun path 300px, Sun path polar chart for any location at the latitude of Rotterdam Sun path, sometimes also called day arc, refers to the daily Daily or The Daily may refer to: Journalism * Daily newspaper A newspaper is a Periodical lit ...
and
Lambert's cosine law In optics Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics ...
). Another passive solar design principle is that thermal energy can be stored in certain building materials and released again when heat gain eases to stabilize
diurnal Diurnal ("daily Daily or The Daily may refer to: Journalism * Daily newspaper A newspaper is a Periodical literature, periodical publication containing written News, information about current events and is often typed in black ink with a ...
(day/night) temperature variations. The complex interaction of
thermodynamic Thermodynamics is a branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related ent ...
principles can be
counterintuitive {{Short pages monitor Home automation systems that monitor temperature, sunlight, time of day, and room occupancy can precisely control motorized window-shading-and-insulation devices.


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 In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. ...

electromagnetic radiation
to determine its
thermal radiation Thermal radiation in visible light can be seen on this hot metalwork. Its emission in the infrared is invisible to the human eye. Infrared cameras are capable of capturing this infrared emission (see Thermography). Thermal radiation is electrom ...
properties of reflection or absorption can assist the choices.
Se
Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory: "Cool Colors"


Landscaping and gardens

Energy-efficient landscaping materials for careful passive solar choices include hardscape building material and "softscape" plants. The use of landscape design principles for selection of trees, hedge (barrier), hedges, and trellis (agriculture), trellis-pergola features with vines; all can be used to create summer shading. For winter solar gain it is desirable to use deciduous plants that drop their leaves in the autumn gives year round passive solar benefits. Non-deciduous evergreen shrubs and trees can be windbreaks, at variable heights and distances, to create protection and shelter from winter
wind chill A chart of wind chill values for given air temperatures and wind speeds Wind-chill or windchill (popularly wind chill factor) is the lowering of body temperature due to the passing-flow of lower-temperature air. Wind chill numbers are always low ...

wind chill
. Xeriscaping with 'mature size appropriate' Native plant, native species of-and Drought tolerance, drought tolerant plants, drip irrigation, mulching, and organic gardening practices reduce or eliminate the need for energy-and-water-intensive irrigation, gas powered garden equipment, and reduces the landfill waste footprint. Solar powered landscape lighting and fountain pumps, and covered swimming pools and plunge pools with Solar water heating, solar water heaters can reduce the impact of such amenities. *Sustainable gardening *Sustainable landscaping *Sustainable landscape architecture


Other passive solar principles


Passive solar lighting

Passive solar lighting techniques enhance taking advantage of Sunlight, natural Daylighting, illumination for interiors, and so reduce reliance on artificial lighting systems. This can be achieved by careful building design, orientation, and placement of window sections to collect light. Other creative solutions involve the use of reflecting surfaces to admit daylight into the interior of a building. Window sections should be adequately sized, and to avoid over-illumination can be shielded with a Brise soleil, awnings, well placed trees, glass coatings, and other passive and active devices.Chiras, D. The Solar House: Passive Heating and Cooling. Chelsea Green Publishing Company; 2002. Another major issue for many window systems is that they can be potentially vulnerable sites of excessive thermal gain or heat loss. Whilst high mounted clerestory window and traditional skylight (window), skylights can introduce daylight in poorly oriented sections of a building, unwanted heat transfer may be hard to control. Thus, energy that is saved by reducing artificial lighting is often more than offset by the energy required for operating HVAC systems to maintain
thermal comfort Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation ( ANSI/ASHRAE Standard 55).ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupanc ...
. Various methods can be employed to address this including but not limited to
window covering Window coverings are considered any type of materials used to cover a window A window is an opening in a wall, door, roof, or vehicle that allows the passage of light and may also allow the passage of sound and sometimes air. Modern windows ar ...
s,
insulated glazing File:EURO 68 wooden window profile with insulated glazing 02.JPG, EURO 68 wooden window profile with insulated glazing Insulating glass (IG) consists of two or more glass Paned window (architecture), window panes separated by a space to reduce he ...
and novel materials such as aerogel semi-transparent insulation, optical fiber embedded in walls or roof, o
hybrid solar lighting at Oak Ridge National Laboratory
Reflecting elements, from active and passive daylighting collectors, such as light shelves, lighter wall and floor colors, mirrored wall sections, interior walls with upper glass panels, and clear or translucent glassed hinged doors and sliding glass doors take the captured light and passively reflect it further inside. The light can be from passive windows or skylights and solar light tubes or from active daylighting sources. In traditional Japanese architecture the Shōji sliding panel doors, with translucent Washi screens, are an original precedent. International Style (architecture), International style, Modern architecture, Modernist and Mid-century modern architecture were earlier innovators of this passive penetration and reflection in industrial, commercial, and residential applications.


Passive solar water heating

There are many ways to use solar thermal energy to heat water for domestic use. Different active-and-passive solar hot water technologies have different location-specific economic cost benefit analysis implications. Fundamental passive solar hot water heating involves no pumps or anything electrical. It is very cost effective in climates that do not have lengthy sub-freezing, or very-cloudy, weather conditions. Other active solar water heating technologies, etc. may be more appropriate for some locations. It is possible to have active solar hot water which is also capable of being "off grid" and qualifies as sustainable. This is done by the use of a photovoltaic cell which uses energy from the sun to power the pumps.


Comparison to the Passive House standard in Europe

There is growing momentum in Europe for the approach espoused by the passive house, Passive House (''Passivhaus'' in German) Institute in Germany. Rather than relying solely on traditional passive solar design techniques, this approach seeks to make use of all passive sources of heat, minimises energy usage, and emphasises the need for high levels of insulation reinforced by meticulous attention to detail in order to address thermal bridging and cold air infiltration. Most of the buildings built to the Passive House standard also incorporate an active heat recovery ventilation unit with or without a small (typically 1 kW) incorporated heating component. The energy design of Passive House buildings is developed using a spreadsheet-based modeling tool called the Passive House Planning Package (PHPP) which is updated periodically. The current version is PHPP 9.6 (2018). A building may be certified as a "Passive House" when it can be shown that it meets certain criteria, the most important being that the annual specific heat demand for the house should not exceed 15kWh/m2a.


Comparison to the Zero heating building

With advances in quadruple glazing, ultra low U-value glazing a Passive House-based (nearly) zero heating building is proposed to supersede the apparently failed nearly-zero energy buildings in EU. The zero heating building reduces on the passive solar design and makes the building more opened to conventional architectural design. The annual specific heat demand for the zero-heating house should not exceed 3 kWh/m2a. Zero heating building is simpler to design and to operate. For example: there is no need for modulated sun shading in zero-heating houses.


Design tools

Traditionally a heliodon was used to simulate the altitude and azimuth of the sun shining on a model building at any time of any day of the year. In modern times, computer programs can model this phenomenon and integrate local climate data (including site impacts such as shadow, overshadowing and physical obstructions) to predict the solar gain potential for a particular building design over the course of a year. GPS-based smartphone applications can now do this inexpensively on a hand held device. These design tools provide the passive solar designer the ability to evaluate local conditions, design elements and orientation prior to construction. Energy performance optimization normally requires an iterative-refinement design-and-evaluate process. There is no such thing as a "one-size-fits-all" universal passive solar building design that would work well in all locations.


Levels of application

Many detached suburban houses can achieve reductions in heating expense without obvious changes to their appearance, comfort or usability. 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 In building design, thermal mass is a property of the mass of a building which enables it to store heat, providing "inertia" against temperature fluctuations. It is sometimes known as the thermal flywheel effect. For example, when outside temperat ...
. 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 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. 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, and other emerging alternative energy sources. Passive solar is also a core building design strategy for passive survivability, along with other passive strategies.


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, 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 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 A Trombe wall is a massive Equator-facing wall that is painted a dark color in order to absorb thermal energy from incident sunlight and covered with a glass on the outside with an insulating air-gap between the wall and the glaze. A Trombe wall is ...

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 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.


See also

*Site analysis, Site Analysis *Daylighting *Energy-plus-house *List of low-energy building techniques *List of pioneering solar buildings *Low energy building *Low-energy house *Earthship *PlusEnergy *Solar architecture *Quadruple glazing ;Energy Rating systems *House Energy Rating (Aust.) *Home energy rating (USA) *EnerGuide (Canada) *National Home Energy Rating (UK)


References


External links


www.solarbuildings.ca
– Canadian Solar Buildings Research Network

– US Department of Energy (DOE) Guidelines *
www.climatechange.gov.au
– Australian Dept of Climate Change and Energy Efficiency
www.ornl.gov
– Oak Ridge National Laboratory (ORNL) Building Technology
www.FSEC.UCF.edu
– Florida Solar Energy Center


www.PassiveSolarEnergy.info
– Passive Solar Energy Technology Overview

– Your Home Technical Manual developed by the Commonwealth of Australia to provide information about how to design, build and live in environmentally sustainable homes.

Energy in Architecture, The European Passive Solar Handbook, Goulding J.R, Owen Lewis J, Steemers Theo C, Sponsored by the European Commission, published by Batsford 1986, reprinted 1993 {{Design Solar design, Energy-saving lighting Heating, ventilation, and air conditioning Low-energy building Sustainable urban planning Renewable energy Solar architecture es:Casa pasiva