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PASSIVE SOLAR HEATING

PASSIVE SOLAR HEATING. Amorim / Simonian. What is Passive Solar Heating ?.

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PASSIVE SOLAR HEATING

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  1. PASSIVE SOLAR HEATING Amorim / Simonian

  2. What is Passive Solar Heating? Passive solar building design is a strategy by which a building’s windows, walls and floors can be designed to collect, storeanddistributesolarenergyin the form of heat in the winter, and vent solar heat in the summer. Passive solar techniques are applied most easily to new construction, but existing buildings can be retrofitted to passively take advantage of the local climate.

  3. Passive Solar Design FIVE PRINCIPLES 1. The Aperture or Collector Area • The sunlight enters the house via the aperture area which is the glass or windows in the house. • The best sun is within 25 degrees of true south. 2. The Absorber Area • The absorber is in the direct line of the sunlight. Can be walls, floors, etc. 3. The Thermal mass • The greaterthe thermal mass the betterthe heat retention. 4. Heat Distribution • Heat is distributed by the normal natural transfer methods: convection, conduction, and radiation. • The use of fans assists the movement of heat by convection. • 5. Solar Control • Sunlight must be controlled in the summer or hot season. • Awnings, overhangs, blinds, and fans control the heat in the summer by preventing heat build up or dissipating the heat. http://www.passivehouseandhome.com

  4. Passive Solar Heating DIRECT SOLAR GAIN INDIRECT SOLAR GAIN Indirect gain is a technique by which thermal energy is stored in an area adjacent to (but not part of) the living space. A thermal mass, such as a Trombe wall, absorbs the sun’s heat energy through glazing, and slowly releases it through convection and conduction. Compared with direct gain, indirect gain experiences a time lag and potential heat losses at night. • Direct gain is the simplest passive solar home design technique. Sunlight enters the house through windows without interference, and the heat collection, storage and distribution all occur within the same space. When light reaches floors and walls, they absorb and store the solar heat. At night, the stored heat energy warms the room through convection and radiation. http://www.nachi.org/passive-solar-building-design.htm

  5. Direct Solar Gain How does Direct Solar Gain work? • A direct gain system includes south-facing • windows and a large mass placed within the • space to receive the most direct sunlight in cold • weather and the least direct sunlight in hot weather. • In this type of system, sunlight passes through the • windows, and its heat is trapped by the thermal mass • in the room. http://www.nachi.org/passive-solar-building-design.htm

  6. Direct Solar Gain How does Direct Solar Gain work? • The absorption of solar energy is most effective through direct radiation. With façade glazing only, the heated room is restricted to a relatively shallow depth, typically no more than 1.5 x the height of the glazing. • Clerestories can extend the solar radiation. It also allows for extra daylight. • The Clerestory roof angle should be approximately the same angle as the sun at the time of the winter solstice. http://www.nachi.org/passive-solar-building-design.htm

  7. Direct Solar Gain • In winter, thermal mass absorbs heat by direct sunlight. At night the process is reversed as thermal mass gives up heat, warming the room by radiation, convection and conduction. • In the summer, thermal mass should be shaded so it draws the warmth from the surrounding air and cools the room. The greater the area of thermal mass, the greater its ability to store heat and maintain a uniform temperature.

  8. Direct Solar Gain • Mass Surface absorption • South facing windows • Skylights • Glass types What systems refer to Direct Solar Gain?

  9. Direct Solar Gain • To warm an interior space naturally, use materials and colors that can absorb solar gain on massive surfaces. • Use lighter materials on other surfaces to reflect the sunlight to the surfaces that can absorb the warmth. Mass Surface Absorption

  10. Direct Solar Gain • South facing windows is a primary principle of passive solar design. • They have access to the sun all year round, while openings on the north, east and west sides are more vulnerable to winter winds and do not receive sunlight consistently. South Facing Windows

  11. Direct Solar Gain • Skylights and additional apertures allow for more daylight and solar gain. • The important factors to consider when placing the aperture are transmissivity, material reflectance, placement, size, room proportion and external obstructions. Skylights

  12. Direct Solar Gain • Windows are a big source of energy flow in a house. • Many windows are single pane or have thinner glass which allow more solar gain. • Double or triple pane windows and glass with reflective coating will reduce solar gain, as well as infiltration and other energy flows. Glass Types SINGLE PANE GLASS DOUBLE PANE GLASS

  13. The Finch house Remodeled by: Doerr Architecture Location: Denver, Colorado • The Finch House before remodel. http://doerr.org

  14. The Finch house Remodeled by: Doerr Architecture Location: Denver, Colorado • South facing windows. • Thin glass was placed high so the neighboring building would not block the low winter sun. • The southern glass is shaded with overhangs that block the summer sun. • To avoid more summer heat gain, little glass was used on the east and west. http://doerr.org

  15. The Finch house Remodeled by: Doerr Architecture Location: Denver, Colorado • The Finch House was remodeled using a Direct Gain Passive Solar System. • It saves over 90% of heating and cooling energy. http://doerr.org

  16. Indirect Solar Gain • Trombe Walls / Water Walls • Movable Insulation • Solar Reflectors • Exterior Surface Color What systems refer to Indirect Solar Gain?

  17. Indirect Solar Gain TROMBE WALLS What is a Trombe Wall? • A thick, south-facing wall (or North facing wall if in the Southern Hemisphere) separated from the outdoors by glass and an air space and made of a material that absorbs heat. • The wall heats up slowly during the day. Then as it cools gradually during the night, it gives off its heat inside the building. • Heat is radiated in the infra red, which is more penetrating and pleasant than the traditional convective forced air heating systems. • First explored and patented (1881) by Edward S. Morse  • Fully developed as an architectural element by French engineer Félix Trombe and architect Jacques Michel(1960s) http://www.greendesigncollective.com/green/one.html

  18. Indirect Solar Gain TROMBE WALLS How does the Trombe Wall Work? • Simple Trombe walls consist of a glass pane against a wall with an air space in between. Two ventsexist, one at the top and one at the bottom of the air space. • During the day the Sun heats first the air in this space, then the solid wall behind. The hot air rises and enters into the room. • The rising air pulls in cooler air from the room below to then be heated. After the sun sets, the now hot wall will still keep heating air and exchanging that heat into the room. • Once the wall is cold, the cold air from outside most stop interacting with the inside, by using a one way flap on the bottom vent to stop the cold coming back into the room and creating a cooling cycle with the room. • Because temperature variations tend to propagate through dense masonry materials (thermal diffusion) at a rate of approximately 1 inch per hour, daytime heat gain will be available at the interior surface of the thermal mass in the early evening when it's needed. • This time lag property of thermal mass, combined with its thermal decrement (dampening of temperature variations), allows the use of fluctuating daytime solar energy as a more uniform night-time heat source.

  19. Indirect Solar Gain TROMBE WALLS How do we stop the Trombe wall to heat the room in the Summer? • Provide shading devices and overhangs. • Open the bottom vent to the outside and close the top wall vent, which creates a solar chimney that sucks air out of your house to the outside. What is the main drawback of TrombeWalls? • The main drawback of solar walls is their heat loss to the outside. • Double glazing (glass or any of the plastics) is adequate for cutting this down in most climates where winter is not too severe (less than 5000 degree days). • Triple glazing or movable insulation is required in colder climates. http://ncict.net/Parameters/WaterHarvesting12.aspx

  20. Indirect Solar Gain TROMBE WALLS Trombe Wall Design Guidelines • Use double glazing - this makes the solar collection of the wall a lot more efficient as more heat is trapped in the inner air space. • Use low-e glass – a special glass which has a lower rate of heat transmission. • Forced fan - use a fan to drive air through the air space, this improves the rate of air exchange. • Dark color - black or a dark color increases heat gain. • Movable blinds - placed over the glass and used to limit solar gain. It also helps with reducing heat loss at night. • Insulation- if the wall areas not behind the glass are insulated on the outside it avoids heat loss at night, improving the longevity of heat gain after dark. • The air space between the thermal mass wall and the glass should be a minimum of 4 inches. • Vents used in a thermal mass wall must be closed at night. • Thermal wall thickness should be about 10-14 inches for brick, 12-18 for concrete, 8-12” for adobeor other earth material and at least 6 inches for water. • TROMBE HOUSE FelizTrombe I Odeillo, France I 1967 • A dense cast-in-place concrete wall forms the south facade. • Its outer surface is pebbled and painted either black or brown to serve as the absorber. • Double glazing mounted in a metal frame is positioned about 4 ¾ “ outside the wall. Air circulation openings are positioned at the top and bottom of the wall.

  21. Indirect Solar Gain WATER WALL How does a Water Wall radiate solar energy? • Similar to a Trombe wall, a water wall collects, stores, then radiatessolar heat. • It must be a southfacing wall (N. Hemisphere) for maximum solar gains. How does a Water Wall compare to a Trombe Wall? • It is a more efficient storage material because it takes up less space (minimum 6 inch thickness) than a trombe wall, it has a better time lag, and it also has cooling capabilities. http://www.greendesigncollective.com/green/one.html

  22. Indirect Solar Gain MOVABLE INSULATION What is Movable Insulation? • Versatile window covering that allows beneficial heat gain during winter, and minimizes unwanted heat gain in summer. • A typical insulated wall has an R-value anywhere from 12 to 19, while a double-pane window has an R-value of about 2. By using movable insulation within the window frame, the R-value nearly doubles. This will help reduce a home's overall heating and cooling load. http://www.greendesigncollective.com/green/one.html

  23. Indirect Solar Gain MOVABLE INSULATION Types of Movable Insulation • Two types: interiorand exterior • The advantages of interior insulation are protection from the weather and simplicity of operation. • The advantages of exterior movable is that they reflect more sunlight into a home during winter months. They also do a better job of reducing solar load in the summer. However, shutters generally cost more than interior insulation, and are subject to constant weathering. • DARMSTADT SOLAR DECATHLON Technische Universität Darmstadt I Germany I 2007 http://www.greendesigncollective.com/green/one.html

  24. Indirect Solar Gain SOLAR REFLECTORS What are Solar Reflectors? • Solar reflectors are panels and other exterior surfaces and materials outside of window openings that reflect sunlight into the space to increase solar gains. • Materials with higher reflectance levels, such as mirrors and polished metal work more efficiently than dull metals. • Reflectors can also be operableto change positions according to seasons. http://www.greendesigncollective.com/green/one.html

  25. Indirect Solar Gain EXTERIOR SURFACE COLOR How do the Exterior Surface Colors contribute to solar gains? • In warmer climates, lighter exterior colors reflect solar radiation, keeping the temperature of the outside surface lower. • In colder climates, dark exterior colors absorb heat from the sun, increasing the exterior surface temperature and reducing envelope heat loss. http://www.greendesigncollective.com/green/one.html

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