In the design of passive solar buildings , windows, walls, and floors are made to collect, store, reflect, and distribute solar energy in the form of heat in winter and reject the heat of the summer sun. This is called a passive solar design because, unlike active solar heating systems, it does not involve the use of mechanical and electrical devices.
The key to designing a passive solar building is to utilize the local climate by conducting accurate site analysis. Elements to be considered include the placement and size of windows, and types of glass, thermal insulation, thermal mass, and shadows. Passive solar design techniques can be applied easily to new buildings, but existing buildings can be adapted or "reassembled".
Video Passive solar building design
Strengthening of passive energy
Passive solar technology uses sunlight without an active mechanical system (as contrast with active sun). Such technology converts sunlight into usable heat (in water, air, and thermal mass), causing air movement for ventilation, or future use, with little use of other energy sources. A common example is the solarium on the side of the equator of a building. Passive cooling is the use of the same design principles to reduce the need for summer cooling.
Some passive systems use a small amount of conventional energy to control dampers, window coverings, night insulation, and other devices that increase the collection, storage, and use of solar energy, and reduce unwanted heat transfer.
Passive solar technologies include direct and indirect solar gain for indoor heating, solar water heating systems based on thermosipones, thermal mass usage and phase change materials to slow changes in indoor air temperature, solar cookers, solar chimneys to enhance natural ventilation, and protection earth.
More broadly, passive solar technologies include solar furnaces, but these typically require some external energy to harmonize mirrors or concentrated recipients, and have historically not been proven to be practical or cost effective for widespread use. The 'low grade' energy needs, such as space and water heating, have proven over time to become better applications for passive use of solar energy.
Maps Passive solar building design
As a science
The scientific basis for the design of passive solar buildings has been developed from a combination of climatology, thermodynamics (especially heat transfer: conduction (heat), convection, and electromagnetic radiation), fluid/natural convection mechanics (passive air and water movement without the use of electricity, fans or pumps) , and the thermal comfort of humans by heat index, psychrometric, and enthalpy controls for buildings inhabited by humans or animals, sunroom, solarium, and greenhouses to raise crops.
Particular attention is divided into: location, location and orientation of the building sun, local solar path, prevailing insolation level (latitude/sunlight/cloud/precipitation), design and quality/construction materials, placement/size/type of windows and walls; incorporation of thermal mass saving solar energy with heat capacity.
While these considerations can be directed to every building, achieving optimized cost/performance optimized solutions requires a careful and holistic integration system integration of these scientific principles. Modern improvements through computer modeling (such as the comprehensive US Department of Energy "Energy Plus" building energy simulation software), and the implementation of decades of learning (since the 1970s energy crisis) can achieve significant energy savings and reduced environmental damage, without sacrificing function or aesthetics. In fact, the features of a solar-like design such as a greenhouse/sunroom/solarium can greatly improve the life-span, daytime, outlook, and home value, at a low cost per unit of space.
Much has been learned about the design of passive solar buildings since the energy crisis of the 1970s. Many unscientific and intuitive expensive construction experiments have tried 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 materials and technologies that are outside the shelf), but a scientifically passive solar building design is a non-trivial engineering effort that requires significant studies of previous counter-intuitive learning, and the time to enter, evaluate, and iteratively refine the input and output simulation.
One of the most useful post-construction evaluation tools is the use of thermography using digital thermal imaging cameras for formal quantitative scientific energy audits. Thermal imaging can be used to document areas with poor thermal performance such as negative thermal impact from roof-to-ceiling glass or skylights on winter evenings or hot summer days.
Scientific lessons learned over the last three decades have been obtained in sophisticated advanced computer systems for advanced energy simulation (such as US DOE Energy Plus).
The design of scientifically passive solar building with product optimization of quantitative cost benefits is not easy for beginners. The level of complexity has resulted in a continuous bad architecture, and many unscientific construction experiments have disappointed their designers and wasted most of their construction budgets on inappropriate ideas.
Economic motivation for scientific design and engineering is very important. If it has been applied comprehensively to new building construction starting in 1980 (based on 1970 lessons), America can save more than $ 250 million annually for expensive energy and related pollution today.
Since 1979, Passive Solar Building Design has become an important element for achieving zero energy by experiments of educational institutions, and governments around the world, including the US Department of Energy, and energy research scientists they have supported for decades. The effective evidence of concepts has been established several decades ago, but the assimilation of culture into the architecture, construction trade, and decision-making of owners has been very slow and difficult to change.
The new term "Architecture Science" and "Architectural Technology" are being added to several Architecture schools, with the aim of teaching future scientific principles and energy-techniques above.
Solar path in passive design
The ability to achieve these goals simultaneously relies heavily on seasonal variations in the sun all day long.
This occurs as a result of the slope of the Earth's axis of rotation in relation to its orbit. The sun line is unique for every latitude.
In the northern hemisphere non-tropical latitudes are further than 23.5 degrees from the equator:
- The sun will reach the highest point southward (towards the equator)
- As the winter solstice approaches, the angle at which the sun rises and sets farther toward the South and the daylight becomes shorter
- The reverse is recorded in the summer where the sun will rise and sunset further north and daylight will extend
The reverse is observed in the Southern Hemisphere, but the sun rises to the east and sets westward regardless of where you are.
In the equatorial region less than 23.5 degrees, the position of the sun at noon the sun will oscillate from north to south and back again throughout the year.
In areas closer than 23.5 degrees from the north-or-south pole, during the summer the sun will track the complete circle in the sky without setting while it will never appear above the horizon six months later, during the peak of winter.
The 47 degrees difference in the sun's heights during the daylight between winter and summer forms the basis of the passive solar design. This information is combined with local climate data (day degree) heating and cooling requirements to determine when the sun's time advantage will be beneficial for thermal comfort, and when it should be blocked with shade. With the strategic placement of items such as glass and shade, the percentage of solar gain that enters a building can be controlled throughout the year.
One of the problems of design of the passive solar sun lanes is that even though the sun is in the same relative position six weeks earlier, and six weeks after that, the solstice, due to the "thermal lag" of the Earth's thermal mass, the temperature and solar acquisition requirements are very different before and after the summer or winter solstice. Movable windows, curtains, color screens, or window sills can accommodate solar and solar insulation day by day and hour by hour.
The careful room arrangements complement the design of the passive sun. The general recommendation for a residence is a residence facing the afternoon sun and a bed on the opposite side. Heliodon is a traditional moving light device used by architects and designers to help model the effects of the sun's path. In modern times, 3D computer graphics can visually simulate this data, and calculate performance predictions.
The principle of passive solar heat transfer
Personal thermal comfort is a function of personal health factors (medical, psychological, sociological and situational), ambient air temperature, mean radiation temperature, air movement (cold wind, turbulence) and relative humidity (affecting human evaporative cooling). Heat transfer in buildings occurs through convection, conduction, and thermal radiation through roofs, walls, floors and windows.
Convective heat transfer
Convective heat transfer can be beneficial or detrimental. Uncontrolled airborne infiltration from bad weather/weatherstripping/draft-proofing can contribute up to 40% of heat loss during winter; however, the strategic placement of windows or movable ventilation may increase convection, cross ventilation, and summer cooling when outside air has a comfortable temperature and relative humidity. A filtered energy recovery ventilation system may be useful for removing unwanted moisture, dust, pollen, and microorganisms in unfiltered air vents.
Natural convection causes warm air rise and a cooler fall of air can result in uneven heat stratification. This may cause uncomfortable temperature variations in the upper and lower cooling chambers, serving as a method of hot air ventilation, or designed as a natural air-convection stream for passive solar heat distribution and temperature equalization. Human natural cooling through sweat and evaporation can be facilitated through convective or forced natural convective air movement by fans, but ceiling fans can disrupt the layers of high-rise insulating air at the top of the room, and accelerate heat transfer from the hot attic, or through nearby windows. In addition, high relative humidity inhibits evaporative cooling by humans.
Radiation heat transfer
The main source of heat transfer is radiation energy, and the main source is the sun. Solar radiation occurs mainly through roofs and windows (but also through walls). Thermal radiation moves from a warmer surface to a cooler one. The roof receives most of the solar radiation delivered to the house. A cool roof, or a green roof next to a luminous barrier can help prevent your attic from becoming hotter than the peak summer heat outside temperature (see albedo, absorptivity, emissivity, and reflectivity).
Windows is a ready and predictable site for thermal radiation. Energy from radiation can move to the window during the day, and out of the same window at night. Radiation uses photons to transmit electromagnetic waves through a vacuum, or a translucent medium. The heat of the sun can be significant even on cold days. The advantages of solar heat through windows can be reduced by insulated glass, shadows, and orientation. Windows are very difficult to isolate compared to the roof and walls. Convective heat transfer through and around the window cover also lowers the insulation properties. When shading windows, external shadows are more effective at reducing heat gain than internal window cover.
The west and east of the sun can provide warmth and lighting, but are prone to overheating in the summer if not shaded. In contrast, the low midday sun easily recognizes light and warmth during the winter, but can easily be shaded with a corresponding long overhang or elbow louvres during the summer and leaves that carry the shade of summer trees that shed their leaves in the fall. The amount of heat of received jets associated with the location of latitude, altitude, cloud cover, and seasonal/hour incidents (see Sun path and Lambert cosine law).
Another passive solar design principle is that heat energy can be stored in certain building materials and released again when heat recovery makes it easy to stabilize diurnal temperature variations (day/night). The complex interplay of thermodynamic principles can be counter-positive for novice designers. Appropriate computer modeling can help avoid costly construction experiments.
Site-specific considerations during design
- Latitude, sun lane, and insolation (sunshine)
- Seasonal variations in solar power generation, e.g. cooling or warming day degrees, solar insolation, humidity
- Daily temperature variation
- Details of the microclimate associated with wind, moisture, vegetation, and soil contours
- Barrier/Over-shadowing - to get the sun or the local wind.
Design elements for residential buildings in temperate climates
- Placement of room types, internal doors and walls, and equipment at home.
- Building-oriented to facing the equator (or some degree to the East to catch the morning sun)
- Expand building dimensions along the east/west axis
- Enough window sizes to face the midday sun in the winter, and shaded in the summer.
- Minimizes windows on the other side, especially west windows
- Determine appropriate roof size, widening roof, or shadow element (shrubs, trees, trellises, fences, shutters, etc.)
- Use appropriate amounts and types of insulation including radiant beams and bulk insulation to minimize excessive heat or shortage
- Using thermal mass to store excessive solar energy during the winter day (which is then irradiated at night)
The exact amount of glass facing the equator and the thermal mass should be based on careful consideration of latitude, elevation, climatic conditions, and the requirements of heating/cooling day levels.
Factors that can reduce thermal performance:
- Deviation from ideal orientation and aspect ratio north/south/east/west
- Excessive glass area ("excess glass") causes excessive heat (also causes glare and waning of soft furnishings) and heat loss when ambient air temperature falls
- Installing the glass where the sun is obtained during the day and heat loss at night can not be controlled easily eg. Facing west, cornered glass, skylight
- Thermal loss through unprotected or unprotected glass
- Lack of adequate shading during high seasonal solar periods (especially on Western walls)
- Incorrect thermal mass application to modulate daily temperature variations
- Open the stairs leading to uneven warm air distribution between up and down floors as warm air rises
- Building surface height is high against volume - Too many angles
- Insufficient weather causes high air infiltration
- Lack of, or improperly installed, barriers beaming during the summer. (See also a cool roof and a green roof)
- Insulating material not matched to the main mode of heat transfer (eg unwanted/conductive heat transfer/unwanted radiation)
Efficiency and economy of passive solar heating
Technically, PSH is very efficient. Direct gain systems can utilize (ie converted into "useful" heat) 65-70% of solar radiation energy that attacks aperture or collector.
Passive solar fraction (PSF) is the percentage of required heat load that is satisfied by PSH and hence a potential decrease in heating costs. RETScreen International has reported PSF 20-50%. In the field of sustainability, energy conservation even from the order of 15% is considered substantial.
Other sources report the following PSF:
- 5-25% for simple systems
- 40% for "highly optimized" system
- Up to 75% for "very strong" system
In favorable climates such as the southwestern United States, highly optimized systems can exceed 75% of PSF.
For more information, see Solar Air Heat
The main passive solar building configuration
There are three primary passive solar energy configurations:
- the direct solar system
- indirect solar system
- an isolated solar system
Direct solar system
In a direct-gain solar pass system , indoor space acts as a solar collector, heat sink, and distribution system. The south-facing glass in the northern hemisphere (facing north in the southern hemisphere) recognizes solar energy into the interior of the building where it instantly heats (absorption of radiant energy) or indirectly heats (through convection) thermal mass in buildings such as concrete or stone floors and walls. Floors and walls that act as thermal mass are incorporated as the functional part of the building and reduce the intensity of heating during the day. At night, the heated hot mass radiates heat into the indoor space.
In cold climates, a sun-breaking building is the most basic type of direct passive solar configuration that involves increasing (slightly) a region of glass facing south, without adding additional thermal mass. This is a type of direct-gain system in which the building envelope is well insulated, extends east-west, and has most (~ 80% or more) of windows on the south side. It has a little extra thermal mass beyond what is already in the building (ie, only framing, wallboard, and so on). In a sun-fortified building, a south-facing window area should be limited to about 5 to 7% of the total floor area, less in a sunny climate, to prevent overheating. The addition of a south-facing glass can be inserted only if more thermal mass is added. Simple energy savings with this system, and sun shooting are very low cost.
In the original direct-gain passive solar system , sufficient thermal mass is required to prevent large temperature fluctuations in the indoor air; more thermal mass is needed than in a hardened building. Overheating the interior of a building may produce insufficient or poorly designed thermal mass. About half to two-thirds of the floor surface area, walls and ceilings should be built from thermal storage materials. Thermal storage materials can be concrete, brick, brick, and water. The thermal mass on the floor and wall must be maintained as closely as possible functionally and aesthetically; Thermal mass needs to be exposed to direct sunlight. Wall-to-wall tapestries, large throwing carpets, spacious furniture, and large wall hangings should be avoided.
Normally, for every 1 ft 2 of the south-facing glass, about 5 to 10 ft 3 of thermal mass is required for thermal mass (1 m 3 per 5 to 10 m 2 ). When taking into account minimal wall and floor coverings up to the average and furniture, this is usually equivalent to about 5 to 10 feet 2 per foot 2 (5 to 10 m 2 per m 2 ) from the south-facing glass, depending on whether direct sunlight is on the surface. The simplest rule of thumb is that the thermal mass area should have an area of ​​5 to 10 times the surface area of ​​the direct collector (glass).
Dense thermal mass (eg, concrete, stone pairs, stones, etc.) Must be relatively thin, no more than about 4 inches (100 mm) thick. Thermal mass with large open areas and those in direct sunlight for at least part of the day (at least 2 hours) performs best. Medium-to-dark, high-absorptive color, should be used on the surface of thermal mass elements that will be in direct sunlight. The thermal mass that is not in contact with sunlight can be any color. Light elements (e.g. Wall and ceiling drywall) can be any color. Covering the glass with insulated panels that can be moved tightly during dark, cloudy periods and nighttime hours will greatly improve the performance of the direct gain system. Water contained in plastic or metal containment and placed in direct sunlight heats faster and more evenly than the solid mass due to natural convection heat transfer. The convection process also prevents the surface temperature from being too extreme as it sometimes happens when the surface of dense dark mass receives direct sunlight.
Depending on the climate and with sufficient thermal mass, the area of ​​the glass facing south in the direct gain system should be limited to about 10 to 20% of the floor area (eg, 10 to 20 ft 2 glass for floor area 100Ã, ft 2 ). It should be based on a clean glass or glass area. Note that most windows have a clean glass/glass area that is 75 to 85% of the overall window area of ​​the window. Above this level, problems with overheating, glare and fading of the fabric tend to be.
Indirect solar system
In the indirect passive solar system , thermal mass (concrete, brick pair, or water) is located just behind the south-facing glass and in front of the heated indoor space and thus no direct heating The mass position prevents sunlight from entering the indoor space and can also block the view through the glass. There are two types of indirect procurement systems: thermal wall storage systems and roof pool systems.
Thermal Storage (Wall Trombe)
In a thermal wall storage system, often called Trombe Wall , the large wall lies just behind the south-facing glass, which absorbs solar energy and selectively releases it into the interior of the building at night. The walls can be constructed from concrete, brick, adobe, stone, or solid (or filled) reinforced concrete units. Sunlight enters through the glass and is immediately absorbed on the surface of the mass wall and is either stored or carried through the material mass to the space inside. The thermal mass can not absorb solar energy as fast as it enters the space between the mass and the window area. The temperature of the air in this space can easily exceed 120 ° F (49 ° C). This hot air can be introduced into the interior spaces behind the wall by inserting a heat supply vent over the top of the wall. This wall system was first envisioned and patented in 1881 by its inventor, Edward Morse. Felix Trombe, who is sometimes named by this system, is a French engineer who built several houses using this design in the French Pyrenees in the 1960s.
A thermal storage wall typically consists of 4 to 16 in thick brick walls (100 to 400 mm) lined with dark, absorbed heat finish (or selective surface) and covered with a single layer or double high transmissivity glass. Glass is usually placed from the 2nd þ dari from the wall to create a small air space. In some designs, the mass lies 1 to 2 ft (0.6 m) from the glass, but the space still can not be used. The surface of the thermal mass absorbs the invading solar radiation and stores it for nighttime use. Unlike direct-gain systems, thermal wall storage systems provide passive, excessive passive solar heating and glare in interior spaces. However, the ability to take advantage of sight and lighting is eliminated. The performance of Trombe walls is reduced if the interior walls are not open for interior space. Furniture, bookcases, and wall cabinets mounted on the inside surface of the walls will reduce their performance.
The classic Trombe wall , also commonly called ventilated thermal storage wall , has a ventilation that can be operated near the sky -the ceilings and floor-level mass walls that allow indoor air to flow through them with natural convection. When solar radiation heats air trapped between glass and walls and begins to rise. The air is drawn into the bottom hole, then into the space between the glass and the wall to be heated by solar radiation, raising the temperature and causing it to rise, and then exit through the upper vents (ceiling) back into the indoor space. This allows the wall to directly introduce hot air into space; usually at a temperature of about 90 ° F (32 ° C).
If ventilation is left open at night (or on cloudy days), convective air flow reversals will occur, throwing away the heat by throwing it outdoors. Ventilation should be closed at night so that the heat radiation from the interior surface of the storage wall heats up the indoor space. Generally, ventilation is also closed during the summer when heat gain is not required. During the summer, outside vents installed at the top of the wall can be opened to vent out. Such ventilation makes the system act as a solar chimney that moves air through buildings during the day.
Ventilated thermal storage walls released into the interior have proved ineffective, especially as they provide too much heat during the day in cool weather and during the summer months; they just overheat and create a comfort problem. Most solar experts recommend that thermal storage walls should not be released into the interior.
There are many variations of the Trombe wall system. An unassessed thermal storage wall (technically not the Trombe wall) captures the solar energy on the outer surface, heats up, and heats the surface of the interior, where it radiates from the surface interior walls to indoor space later on. A water wall uses a type of thermal mass consisting of a tank or water tube used as a thermal mass.
Unventilated thermal storage walls comprise a south-facing brick wall or concrete wall with a material that absorbs heat on the exterior surface and is faced with a single or double glass layer. High transmission glass maximizes solar gain to mass wall. Glass is placed from Ã,¾ to 6 inches (20 to 150 mm) from the wall to create a small air space. Glass framing is usually metal (for example, aluminum) because the vinyl will soften and the wood will become super dry at 180 ° F (82 ° C) which can be behind the glass on the wall. The heat from the sunlight passing through the glass is absorbed by the dark surface, deposited on the wall, and done slowly inward through the masonry. As architectural detail, patterned glass can limit the visibility of the outer walls without compromising the transmissivity of the sun.
The water wall uses a water container for thermal mass, not a solid mass wall. Water walls are usually slightly more efficient than solid wall masses because they absorb heat more efficiently due to the development of convective currents in liquid water when heated. This current causes rapid mixing and faster heat transfer into the building than can be provided by solid mass walls.
Temperature variations between the exterior and interior wall surfaces propel heat through the mass walls. Inside the building, however, the daytime heat rise is delayed, only becoming available on the interior surface of the thermal mass during the night when necessary because the sun has set. The time interval is the time difference between when the sun first strikes the wall and when heat enters the building's interior. The time interval depends on the type of material used in walls and wall thickness; a larger thickness produces a larger time lag. The time lag character of the thermal mass, combined with the temperature fluctuation damper, allows the use of daylight solar energy as a more uniform nighttime heat source. Windows can be placed on walls for natural lighting or aesthetic reasons, but these tend to decrease efficiency somewhat.
Thermal storage wall thickness should be about 10 to 14 inches (250 to 350 mm) for bricks, 12 to 18 in (300 to 450 mm) for concrete, 8 to 12 in (200 to 300 mm) for soil/adobe, 6 in (150 mm) for water. This thickness delayed the movement of heat so that the temperature of the inner surface reached its peak during the curfew. The heat will take about 8 to 10 hours to reach the inside of the building (heat goes through concrete walls at about an inch an hour). A good thermal connection between inner wall finish (eg, drywall) and thermal mass wall is required to maximize heat transfer to interior space.
Although the position of the thermal wall wall minimizes outdoor heating time during the day, a well-insulated building should be limited to about 0.2 to 0.3Ã, ft 2 from the surface of the thermal mass wall per foot 2 heated floor area (0.2 to 0.3 m 2 per m 2 of floor area), depending on climate. The water wall should have about 0.15-0,2Ã, ft 2 of the water wall surface per foot 2 (0.15 to 0.2 m 2 per m 2 ) of the floor area.
Thermal mass walls are well suited for bright winter climates that have high temperature changes during the day (day and night) (eg, southwest, mountain-west). They do not perform well in cloudy or very cold weather or in climates where there is no large diurnal temperature swing. Thermal night loss through thermal mass of the walls can still be significant in cloudy and cold climates; walls lose heat stored in less than a day, and then emit heat, which dramatically increases the need for heating the reserves. Covering the glass with a tightly moveable insulation panel during long foggy periods and curfew will improve the performance of thermal storage systems.
The main disadvantage of thermal storage walls is the loss of their heat to the outside. Double glass (glass or plastic) is needed to reduce heat loss in most climates. In mild climates, single glazing is acceptable. Selective surfaces (high/low emission absorbing surfaces) applied to the outer surface of the thermal storage wall improve performance by reducing the amount of infrared energy being re-emitted through glass; typically, it achieves similar performance improvements without the need for daily installation and removal of isolation panels. The selective surface consists of a sheet of metal foil attached to the outer surface of the wall. It absorbs almost all radiation in the visible part of the solar spectrum and emits very little in the infrared range. High absorption will convert light to heat on the wall surface, and low transmit power prevents heat radiating back into the glass.
Roof Pool System
A roof the passive solar system , sometimes called the solar roof , uses water stored on the roof to temper the hot and cold internal temperatures, usually in desert environments. Usually built containers that hold 6 to 12 in (150 to 300 mm) of water on a flat roof. Water is stored in large plastic bags or fiberglass containers to maximize emission and minimize evaporation. It can be left without glaze or can be covered by glass. Solar radiation heats up water, which acts as a thermal storage medium. At night or during overcast weather, the container can be closed with an insulation panel. The indoor space under the roof pool is heated by the heat energy emitted by the storage of the roof pool above. The system requires a good drainage system, driven insulation, and an enhanced structural system to support 35 to 70 l/feet of 2 (1.7 to 3.3 kN/m 2 ) dead load.
With a sunlight viewing angle during the day, the rooftop pool is only effective for heating in the lower and middle latitudes, in hot to moderate climates. Roof pool systems perform better for cooling in hot and low humidity climates. Not many solar roofs are built, and there is limited information about the design, cost, performance, and details of thermal storage roof construction.
Solar System Isolated
In the passive isolated gain of the solar system , components (eg, collectors and thermal storage) are isolated from the indoor area of ​​the building.
An attached sunspace , also sometimes called solar space or solarium > , is an isolated type of solar system with an interior space or a glass chamber that is part of or attached to a building but can be completely enclosed from the main occupied area. It functions like an attached greenhouse that utilizes a combination of direct gain and indirect gain system characteristics. A solar room can be called and looks like a greenhouse, but a greenhouse is designed to cultivate plants while the sun room is designed to provide heat and aesthetics to a building. Sunspaces are very popular passive design elements because they extend the living space of the building and offer space for growing crops and other vegetation. In temperate and cold climates, however, additional room heating is required to keep the plants from freezing during very cold weather.
The south-facing sunspace glass collects solar energy as in the direct gain system. The simplest sunspace design is to install a vertical window without glass above the head. The sun spaces may experience a high increase of heat and high heat loss through abundant glass. Although horizontal glass and tilt collect more heat in winter, it is minimized to prevent overheating during the summer months. Although the glass above it can be aesthetically pleasing, the insulated roof provides better thermal performance. Skylights can be used to provide some of the potential for natural light. Vertical glass can maximize the gain in winter, when the sun's angle is low, and produce less heat during the summer. Vertical glass is cheaper, easier to install and insulated, and not vulnerable to leaking, foggy, broken, and other glass. The combination of vertical glass and some sloping glass is acceptable if summer shadows are provided. A well-designed overhang may be all that is needed for a glass shade in the summer.
Temperature variations caused by heat loss and gain can be moderated by thermal mass and low emissivity windows. The thermal mass may include masonry floors, masonry split walls, or water containers. The heat distribution to the building can be achieved through ventilation of ceilings and floors, windows, doors, or fans. In the general design, the thermal mass wall located at the back of the sun room adjacent to the living space will function like an indirect thermal mass wall. The energy of the sun entering the solar space is maintained in the thermal mass. The heat of the sun is brought into the building through conduction through the common mass wall at the rear of the solar chamber and by the ventilation (such as an unventilated thermal storage wall) or through a hole in the wall allowing the flow of air from the sun space to the inner chamber by convection thermal storage is ventilated).
In cold climates, double glazing should be used to reduce conductive losses through outward glass. The nighttime heat loss, although significant during winter, is not so important in the sun space as with the direct acquisition system because the sun space can be closed off the entire building. In temperate and cold climates, isolating thermal sunlight from buildings during the night is important. Large glass panels, French doors, or sliding glass doors between buildings and installed sun rooms will maintain an open feeling without heat loss associated with open spaces.
A sunspace with masonry masonry walls will require about 0.3Ã, ft 2 from the surface of the thermal mass wall per ft 2 of the heated floor area (0.3 m 2 per m 2 of floor area), depending on climate. The wall thickness should be similar to the thermal storage wall. If a water wall is used between the sun and living space, about 0.20Ã, ft 2 from the surface of the thermal mass wall per ft 2 of the heated floor area (0.2 m 2 per m 2 of the floor area) accordingly. In most climates, ventilation systems are needed in summer to prevent overheating. Generally, large (horizontal) and eastern and western overhead areas should not be used in the sun room without special precautions for overheated summer such as using heat reflecting glass and providing a summer shadow system area.
The internal surface of the thermal mass must be dark in color. Movable isolation (eg window coverings, curtains, window coverings) can be used to help trap warm air in the sun room after sunset and during cloudy weather. When closed during very hot days, the window coverings can help keep the sunspace from overheating.
To maximize comfort and efficiency, non-glass sunspace walls, ceilings and foundations must be well insulated. The perimeter of the foundation wall or plate should be insulated into the frost line or around the floor plate. In temperate or cold climates, the east and west walls of the solar space should be isolated (no glass).
Additional measurements
Steps should be taken to reduce heat loss during the night such as window coverings or moving windows insulation.
Heat storage
The sun does not shine all the time. Thermal storage, or thermal mass, keeps the building warm when the sun can not heat it.
In the sun's house during the day, storage is designed for one or more days. The usual method is a specially constructed thermal mass. These include Trombe walls, ventilated concrete floors, water tanks, water walls or rooftop pools. It is also feasible to use the thermal mass of the earth itself, whether as it is or by incorporating into structures with banking or using the earth as a structural medium.
In subarktic areas, or long-term areas without solar gain (eg fog weeks), specially constructed thermal mass is very expensive. Don Stephens pioneered experimental techniques to use the soil as a thermal mass large enough for annual heat storage. The design runs an isolated thermosiphon 3 m below the house, and isolates the soil with a waterproof skirt of 6 m.
Isolation
Thermal or superinsulated insulation (type, placement and amount) reduces unwanted heat leakage. Some of the actual passive buildings are built from isolation.
Custom glass system and window cover
The effectiveness of a direct solar gain system is significantly enhanced by insulative (eg double glazing), spectral selective glass (low-e), or movable window insulation (window quilts, interior bifold insulation shutters, shades, etc.).
Generally, the window facing the Equator should not use a layer of glass that inhibits the acquisition of the sun.
There is a lot of use of super-insulated windows in German Passive House standards. Selection of different spectrum window coatings depends on the heating ratio versus the degree of cooling day for the design site.
Glazing selection
Glass facing the equator
The requirements for glass facing the vertical equator differ from three other sides of a building. The reflective window layers and some glass panels can reduce the useful benefits of the sun. However, the direct gain system depends more on double glazing or triple glass to reduce heat loss. Indirect gain and isolated gain configuration may still work effectively with only one-panel glazing. Nevertheless, the optimal cost-effective solution is location and system dependent.
Glass roof angle and skylight
Skylights acknowledge direct, loud direct sunlight overhead and glare either horizontally (flat roof) or pitched at an angle similar to the roof slope. In some cases, horizontal skylights are used with reflectors to increase the intensity of solar radiation (and hard glare), depending on the angle of the roof. When the winter sun is low on the horizon, most of the solar radiation bounces off the roof glass angle (the angle of its appearance is almost parallel to the morning and evening roof glasses). When the summer sun is high, it is almost perpendicular to the roof-angled glass, which maximizes solar acquisition at the wrong time of year, and acts like a solar furnace. Skylights should be covered and well insulated to reduce natural convection (warm air rises) heat loss during winter evenings, and strong solar heat during spring/summer/fall.
The side facing the equator of a building is south in the northern hemisphere, and north in the southern hemisphere. Skylights on the roof facing away from the equator provide most of the indirect illumination, except for the summer days when the sun can rise on the non-equatorial side of the building (at some latitude). The skylight on the eastern-facing roof provides direct sunlight and maximum solar heat on a summer morning. The west-facing skylights provide afternoon sun and heat during the hottest part of the day.
Some skylights have expensive glass that can partially reduce the heat recovery of the summer sun, while still allowing some visible light transmission. However, if visible light can pass through it, there may be some radiating heat (both are electromagnetic radiation waves).
You can reduce some of the unexpected heat of summer sun's heat by installing skylights under the shade of leaves (leaves), or by adding insulated, opaque window covering inside or outside the skylight. This will eliminate the benefits of daylight in the summer. If a tree limb hangs over the roof, they will raise the problem with the leaves in the rain gutter, possibly causing the ice dam to damage the roof, shorten the life of the roof, and provide an easier path for pests to enter your attic. The leaves and twigs in the skylights are unappealing, difficult to clean, and can increase the risk of broken glass in a windstorm.
"Glass roof saws" with vertical glass alone can bring some of the benefits of passive solar building design into the core of commercial or industrial buildings, without the need for roof or skylight.
Skylights provide daylight. The only display they provide is basically upright in most applications. Well-insulated light tubes can bring sunlight into the northern room, without using skylights. A solar-passive greenhouse provides abundant sunshine for the equatorial side of the building.
Thermal color thermal imaging thermography cameras (used in formal energy audits) can quickly document negative negative impacts of roof-to-ceiling glass or skylights on winter nights or on summer days.
The US Department of Energy stated: "Vertical glass is the best overall choice for sunspaces." Glass brackets and sidewalls are not recommended for passive sunspaces.
US DOE explains weaknesses in roof-angled glass: Glass and plastic have little structural strength. When mounted vertically, glass (or plastic) bears its own weight because only a small area (top edge of glass) is subject to gravity. When the glass is tilted from the vertical axis, however, the increased area (now oblique sectional) of the glass must bear the force of gravity. Glass is also fragile; not much flexing before breaking. To overcome this, you should usually increase the thickness of the glass or increase the amount of structural support to hold the glass. Both increase the overall cost, and the latter will reduce the amount of sun that enters the sun space.
Another common problem with tangled glass is the increased exposure to the weather. It's hard to keep a good seal on the roof-angled glass in intense sunlight. Hail, hail, snow, and wind can cause material damage. For passenger safety, regulators usually require slant glass to be made of safety glass, laminated, or a combination thereof, which reduces the potential for diesel fuel. Most of the roof-angled roofs in the Crowne Plaza Hotel Orlando Airport sun room are destroyed in a single storm. Glass elbow roof increases construction costs, and can increase insurance premiums. Vertical glass is less susceptible to weather damage than right-angled glass.
It is difficult to control the acquisition of solar heat in the sun room with slanted glass during the summer and even during the middle of a bright and sunny winter day. Skylight is the antithesis of zero energy building Passive Solar Cooling in climate with AC requirements.
Incident radiation angle
The amount of solar gain transmitted through glass is also affected by the incidence angle of solar radiation. Sunlight striking a single sheet of glass in 45 degrees perpendicular is mostly transmitted (less than 10% reflected), while for bright sunlight at 70 degrees from perpendicular over 20% of reflected light, and above 70 degrees this percentage is reflected sharply.
All of these factors can be modeled more precisely with photographic and heliodon light gauges or optical benches, which can measure the ratio of reflectivity to transmissivity, based on incident angles.
Alternatively, passive solar computer software can determine the impact of the solar path, and the days of cooling-and-heating degree on energy performance.
Operable shading and insulation devices
Glass-faced designs facing the equator may cause excessive winter, spring, or autumn healings, uncomfortable living spaces at certain times of the year, and excessive heat transfer on winter and summer evenings.
Although the sun is at the same 6-week altitude before and after the solstice, the requirements of heating and cooling before and after the turning point are significantly different. The heat storage at the Earth's surface causes "thermal lag." Variable cloud cover affects the potential for diesel fuel. This means that fixed-latitude windows overhangs, while important, are not complete seasonal solar control solutions.
Control mechanisms (such as insulated curtains inside or outside of manual motorization, window coverings, exterior roll-down shutter screens, or retractable awnings) can compensate for differences caused by thermal or cloud cover densities, and help control variations in daily/hourly earning requirements sun.
Home automation systems that monitor temperature, sunlight, daylight, and occupancy can precisely control window-shading-and-insulating motor devices.
Exterior colors reflect - absorb
Materials and colors can be selected to reflect or absorb solar thermal energy. Using information about Colors for electromagnetic radiation to determine the nature of the heat radiation from reflection or absorption may help the choice See Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory: "Cool Colors"
Landscapes and gardens
Energy-saving landscaping materials for careful passive solar options include hardscape and softscape plants. Use of landscape design principles for tree selection, hedging, and trellis-pergola features with vines; all can be used to create summer shadow. To get the winter sun, it is expected to use leaf crops that drop its leaves in the fall provides passive benefits of the sun throughout the year. Clovers and fallen green trees can be windbreaks, at varying altitudes and distances, to create protection and protection from winter winds. Xeriscape with 'adult-sized native species' and drought-tolerant plants, drip irrigation, mulch, and organic gardening practices reduce or eliminate the need for energy-and-water-intensive irrigation, gas-powered garden equipment, and reduced landfill waste. Solar landscape lighting and fountain pumps, as well as enclosed pools and swimming pools with solar water heaters can reduce the impact of the facility.
- Continent gardening
- Continuous landscape
- Continuous landscape architecture
Other passive solar principles
Passive solar lighting
Passive solar lighting techniques increase the use of natural lighting for the interior, thus reducing the dependence on artificial lighting systems.
This can be achieved with careful building design, orientation, and the placement of the window sections to collect light. Another creative solution involves the use of surface reflections to incorporate sunlight into the building's interior. The window sections should be of sufficient size, and to avoid over-illumination can be protected with Brise soleil, awnings, well-placed trees, layers of glass, and other passive and active devices.
Another major problem for many windows systems is that they can be sites that are potentially vulnerable to excessive heat excess or heat loss. While clerestory windows are mounted high and traditional skylights can introduce daytime in poorly built sections, unwanted heat transfer may be difficult to control. Thus, the energy saved by reducing artificial lighting is often more than offset by the energy required to operate the HVAC system to maintain thermal comfort.
Various methods may be used to overcome this including but not limited to window coverings, insulated glass and new materials such as semi-transparent air insulation, wall-mounted or roof-mounted optical fibers, or hybrid solar lighting at Oak Ridge National Laboratory.
Reflects the elements, from active and passive lighting collectors, such as lamp shelves, lighter walls and floor colors, mirrored wall sections, interior walls with glass top panels, and translucent or translucent glassed glass doors and sliding glass doors take the captured light and passively reflects deeper inside. Light can come from passive windows or skylights and sunlight tubes or from active light sources. In traditional Japanese architecture, Shi Ji's sliding door panels, with a see-through Washi screen, are an original precedent. Modern style, modernist and medieval architecture is the earliest innovator of penetration and passive 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 purposes. Different active and passive solar hot water technologies have different location-specific cost-economy benefit implications.
Passive solar hot water heating basically does not involve any pump or electricity. It's very effective in climates that do not have the old, or very overcast, frost conditions. Other active solar water heating technology, etc. May be more suitable for multiple 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 using photovoltaic cells that use energy from the sun to power the pump.
Comparison with Passive Household standards in Europe
There is a growing momentum in Europe for the approach adopted by Passive House ( Passivhaus in Germany) Institute in Germany. Rather than rely solely on traditional passive passive design techniques, this approach seeks to utilize all passive heat sources, minimize energy use, and emphasizes the need for high levels of insulation reinforced by meticulous attention to detail to overcome thermal connections and cold air infiltration. Most buildings built with Passive House standards also incorporate an active heat recovery ventilation unit with or without integrated heating components (usually 1 kW).
Passive House building energy designs were developed using a spreadsheet-based modeling tool called Passive Home Planning Packages (PHPP) that are updated regularly. The current version is PHPP2007, where 2007 is the year of publication. A building can be certified as a "Passive Home" when it can be shown that it meets certain criteria, most importantly is that annual specific annual heat demand for homes should not exceed 15kWh/m 2 a.
Design tools
Traditionally heliodon is used to simulate the altitude and azimuth of the sun that shine on model buildings anytime of the day throughout the year. In modern times, computer programs can model these phenomena and integrate local climate data (including site impacts such as shadowing and physical barriers) to predict the potential benefits of sun for a particular building design over the course of a year. GPS-based smartphone applications can now do this cheaply on handheld devices. These design tools provide passive solar designers the ability to evaluate local conditions, design elements and pre-construction orientation. Optimization of energy performance usually requires an iterative design-and-evaluation process. There is no such thing as a "one-size-fits-all" universal passive solar building design that will work well in all locations.
Application level
Many separate suburban homes can achieve a reduction in heating costs without a clear change in their appearance, comfort or usefulness. This is done by the placement of good treads and windows, a small amount of thermal mass, with good insulation-but-conventional, weather, and occasional additional heat sources, such as a central radiator connected to a solar water heater. Sunlight can fall on the wall during the day and raise the temperature of thermal mass. It will then radiate heat into the building at night. External shading, or radiation barriers plus air gaps, can be used to reduce the acquisition of undesirable summer sun.
An extension of the "passive solar" approach to catch the seasonal sun and heat storage and cooling. This design seeks to capture the heat of the summer sun, and takes it to a seasonal thermal shop for use a few months later during the winter ("annual passive solar.") Increased storage is achieved by using a large amount of thermal mass or earth clutch. Anecdotal reports suggest they can be effective but no formal research is done to demonstrate their superiority. This approach can also move cooling to warmer seasons. Example:
- Passive Annual Heat Storage (PAHS) - by John Hait
- Heatized Solar Heating (AGS) yearly - by Don Stephen
- Excavated roof
A purely passive "solar-heated home" will not have a mechanical furnace unit, relying only on sunlight-captured energy, plus only "incidental" heat energy released by lights, computers and other task-specific equipment (such as for cooking , entertainment, etc.), showers, people and pets. Use of natural convection air currents (not fan-like mechanical devices) to circulate the associated air, although not completely solar design. Passive solar building designs sometimes use limited electrical and mechanical controls to operate dampers, window insulation, shade, awnings, or reflectors. Some systems ask for small fans or solar heat chimneys to improve convective airflow. A reasonable way to analyze this system is by measuring its performance coefficients. A heat pump may use 1 J for every 4 J giving COP of 4. A system that uses only 30 W fan to distribute more evenly 10 kW of solar heat through the whole house will have COP 300.
Passive solar building designs are often the basic elements of zero-cost energy development. Although ZEB uses some passive passive building design concepts, ZEB is usually not entirely passive, has an active mechanical renewable energy generating system such as: wind turbines, photovoltaics, micro hydro, geothermal, and alternative energy sources emerging.
Passive solar design in a skyscraper
Recently there has been interest in exploiting large amounts of surface area on skyscrapers to improve overall energy efficiency. As more skyscrapers in urban environments, but require large amounts of energy to operate, there is the potential for huge energy savings by using passive solar design techniques. One study, which analyzed the proposed 23 Bishopsgate towers in London, found that 35% of the theoretically decreased energy demand could be achieved through indirect solar gain, by rotating the building to achieve optimal daytime ventilation and penetration, the use of high thermal mass floor materials. to decrease the temperature fluctuations in the building, and use low-emissivity glass windows double or triple glaze to get direct diesel. Indirect solar gain techniques include moderating the flow of wall heat with wall thickness variation (from 20 to 30 cm), using window glass in outer space to prevent heat loss, dedicating 15-20% of floor area for heat storage, and applying Trombe. wall to absorb the heat entering the room. Overhangs are used to block direct sunlight in summer, and leave it in the winter, and heat-reflecting curtains are inserted between thermal walls and glass to limit heat buildup in summer.
Another study analyzed a dual green skin facade (DGSF) outside a high-rise building in Hong Kong. Such as a green facade, or vegetation covering the outer wall, can combat the use of very AC - as much as 80%, as the researchers found.
In temperate regions, strategies such as glass, window-to-wall ratio adjustment, sun shading and roof strategy can offer considerable energy savings, in the range of 30% to 60%.
See also
- Energy Rating System
- H
Source of the article : Wikipedia
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