3C.1 Passive Solar Design National Sustainable Building Advisor Program

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1 3C.1 Passive Solar Design National Sustainable Building Advisor Program Pablo La Roche PhD

2 Passive Cooling

3 But first. Strategies to Reduce Overheating

4 Minimize Conductive Heat Flow Strategies to minimize conductive heat flow: 1. Adding insulation 2. Reducing exposed surface 3. Reducing temperature difference between the indoors and the outdoors.

5 Reduction of Heat Losses by Convection: Types of Ventilation Minimize Heat Flow by Infiltration Reduce the heat flow by convection when the temperature is higher outside than inside.

6 Minimize Solar Gain The effect of solar radiation on the building constitutes the largest single source of thermal gain. Reduce heat gains through transparent and opaque areas of the envelope.

7 Minimize Internal Gains Reduce the heat sources inside the building: the heat gains from the occupants the heat generated by the electrical equipment the heat output from the lamps.

8 Minimize Heat Gains around the Building Natural (vegetation) and artificial (constructed) objects affect the microclimate conditions of the exterior and can be used to avoid overheating of the exterior.

9 But all of those strategies do not cool, they reduce overheating

10 Passive Cooling Systems These transfer heat from the building to natural energy sinks, such as the air, water, earth or outer space. Implementation of these systems in buildings reduces energy needed for cooling.

11 Passive Cooling Systems There are several forms of classifying Passive Cooling Systems; one of them is according to the different heat sinks (Givoni, 1994). According to Cook (1995) the three heat sinks of nature are: The sky, The atmosphere The earth. These heat sinks offer an opportunity to balance energy inputs from the sun. They are the thermal dumps, not only of passive systems, but also of all mechanical systems.

12 Passive Cooling Systems Different systems can take advantage of these heat sinks. Passive Cooling System Comfort Ventilation Nocturnal Ventilative Cooling Radiant Cooling Direct Evaporative Cooling Indirect Evaporative Cooling Heat Sink Ambient Air Ambient Air Upper Atmosphere Ambient Air Ambient Air Soil cooling Undersurface Soil

13 Cooling the Body. Comfort Cooling Comfort is improved by providing a higher airspeed, which helps to increase the efficiency of sweat evaporation. Comfort ventilation is applicable when still air temperatures seem to be too warm, because air movement extends the comfort zone upwards beyond the limit for still air. This air motion can be caused by ventilating a building, but can also be produced by circulating air using a ceiling or portable room fan.

14 Archetype

15 Applicability of Comfort Cooling.

16 Admit Breeze at Body Height

17 Natural Ventilation: For natural ventilation to occur there must be a pressure difference between the entry and the outlet. (+) (-) (-) (-) (-) (-) (-) (+) (-)

18 Location of Inlets and Outlets Figures from La Roche et al 2001 The location of the inlet affects airflow patterns more than the location of the outlet.

19 Window Placement for Comfort Ventilation For comfort ventilation the openings should be at the level of the occupants. Higher openings vent the hot air collecting near the ceiling and are most useful for night flushing.

20 Warm and Humid

21 Planning in Warm and Humid Climates Oil Company Camp & Parajauno Indian Settlement

22 Paraujano House in Hot Humid Climate in Venezuela.

23 Hawaii

24 Hawaii

25 Dutch Oil Company House and Piaroa Churuata

26 Shell House.

27 Furniture

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29 Colonial Rancho, Venezuela

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31 EDITT Tower. T.R. Hamzah and Yeang

32 Villanueva. Venezuela

33 Cooling the Structure of the Building: Nocturnal Ventilative Cooling The building is cooled at night, lowering the temperature of its internal mass by convection. During the day the building is closed, reducing heat gains from the outdoors, while the internal mass acts as a heat sink, keeping the building from warming up.

34 Nocturnal Ventilative Cooling

35 Nocturnal Ventilative Cooling With nocturnal ventilative cooling the building mass is cooled during the night by the outside air. During the day, the night cooled mass acts as a heat sink. Light colors, insulation, shading and closed windows keep the heat gain to a minimum. Interior fans can be used for additional comfort.

36 Archetype: Hot and Dry Climate

37 Applicability of Nocturnal Ventilative Cooling This strategy is applicable mainly in regions with a diurnal temperature swing of more than 15 C (27 F), especially arid regions where the daytime temperatures are between 32 and 36 C (90 97 F) and the night temperatures are about or below 20 C (68 F) to enable sufficient nocturnal cold storage.

38 The building should keep the warm air out.

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40 Cosanti Paolo Soleri

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42 Wind Towers Cooling towers for Phoenix, Arizona Project by Jeff Cook

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44 Passive Solar is the only strategy that cools or heats a building for free without generating GHG

45 Tons of CO 2 that could be reduced per 1000 dwellings with passive tons of C02 cooling per 5000 dwellings: (lbs/mwh) Tons of CO2 per 1000 dwellings tons of C02 per 5000 dwellings: Beiing(China) Santa Monica Uganda Tijuana(Mexico) Venezuela Albuquerque(NM) Rancho Cucamonga Miami (Fl) SMC Source: National Students: Sustainable E Ezell, Building Y Advisor Oo, L Program Felton in Pablo Cal La Poly Roche Pomona P3 team (La Roche, Fox & Nelson, Instructors)

46 Three Step Design for Sustainable Architecture The design of heating, cooling and lighting of buildings in warm countries should follow three steps. The first step is to design the building to minimize heat gain in the summer using natural light efficiently. The second step involves the transfer of energy to natural heat sinks through passive cooling and heating. The third step consists of the design of the mechanical equipment to reduce the remaining thermal loads, using as much renewable energy as possible.

47 Passive Heating for Low Carbon Buildings

48 Heat Loss in the Winter In the winter, the building can loose heat by conduction and convection (infiltration) (Figure by Egan)

49 and gain heat by radiation

50 Solar radiation is the best free heating system available.

51 In Winter we must: Minimize Conductive Heat Flow Minimize Ventilation (Infiltration) Promote Solar Gain

52 Minimize Conductive Heat Flow The best way to minimize conductive heat flow is by adding insulation in the different envelope components.

53 Minimize Heat Flow by Infiltration Since the temperature outside can be much lower than the inside temperature it is very important to reduce the heat flow by ventilation (reduce infiltration). Seal the envelope. The best way to reduce the heat losses by ventilation in a building in the winter is to reduce the heat losses through all the cracks in the building. Leakage can occur through many parts of the building and some of the most common are the bottom of the drywall, the window, and through the plumbing and electrical fixture conduits.

54 Reduction of Infiltration and IAQ It is important that the rate is not reduced so much that it affects the indoor quality of the space. Because of toxic emissions from occupants (CO2) and construction materials in the building, there has to be some exchange of air between the interior and the exterior of a building. There are several ways to express this need, either in cubic feet per minute per person, or air changes/hour. The minimum requirement for IAQ is around 0.5 air changes/hour in single family houses. Adequate IAQ is necessary health requirement in all climates.

55 Andes Mountains

56 Andes Mountains

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58 The GLA Building, London, UK..

59 Greater London Authority Headquarters

60 Increase Heat Flow by Radiation: Passive Solar Heating Heat losses can be reduced by increasing the insulation, reducing the surface area towards the outside and reducing the infiltration rate. But even though these strategies will reduce the heat losses, they will not actually raise the indoor air temperature. The best way to passively increase the average indoor air temperature in the winter is to increase solar gains. This is done through passive solar systems. Energy flows into the building so that its temperature is raised.

61 Passive Solar Heating Passive solar systems must have a medium of achieving solar gains and storing this energy. These systems will capture heat during the day (solar radiation) and store it for night use. For this they must have mass on the inside and insulation on the outside.

62 Direct Gain Systems The simplest passive solar heating system is a direct gain system. This is basically a well insulated house with a large area of south facing windows. Sunshine enters the living space and falls onto the thermal storage mass where it is stored to be re emitted later. Thus the living space where the mass has been stored is a live-in collector. The requirements for these systems are: large south facing glazing with the living space directly behind; exposed thermal mass in the ceiling and or floor and or walls, sized with enough capacity for thermal storage and positioned for solar exposure. Double glazing is used to reduce the losses at night.

63 Direct Gain System

64 Advantages of Direct Gain Systems Very simple to conceptualize and build. You can create a direct gain system by simply relocating windows. The large areas of glazing admit not only solar radiation, but also natural light and visual connections with the outside Glazing is readily available and so it is easy to build. The whole system can be relatively cheap

65 Disadvantages of Direct Gain Systems Large areas of glazing can result in glare by day and loss of privacy by night Ultraviolet radiation from the sunlight can degrade fabrics and photographs To be effective large areas of glazing and large amounts of mass are needed. This mass can be expensive if it does not serve any structural purpose. Even with mass, diurnal temperature swings or 10 K are common. Night time insulation in the solar aperture is needed if the outdoor night temperature is very low.

66 Indirect Gain Systems These systems combine the collection, storage and distribution functions within some part of the building envelope that encloses the living spaces. The most common of these systems are: Trombe wall, Mass wall, Water wall and Roof pond.

67 Indirect Gain: Trombe Wall Solar radiation falls on the mass wall and is absorbed by it, causing the surface of the masonry to warm up. This heat is transferred to the inner surface of the wall by conduction, from where it radiates and is convected to the interior space. The time lag and dampening of the wall depend on the type and thickness of material. A rough estimate is 45 minutes per inch of material. The Trombe wall allows for the distribution of the collected air (which can reach 60 C) by natural convection through the top and bottom vents. These can be closed at night to prevent reverse circulation.

68 Indirect Gain: Trombe Wall

69 Indirect Gain Systems: Trombe Wall The SERF's Trombe wall.

70 Indirect Gain: Mass Wall In the mass wall systems, the thermal storage mass for the building is also a south-facing wall of masonry or concrete construction with the external surface glazed to reduce heat losses to the outside. The difference between a mass and a Trombe wall is that the later has vents at the top and bottom to allow the air to circulate through the interior space and the mass wall only transmits the heat by conduction to the interior surface and then radiation to the space.

71 Indirect Gain Systems: Water Wall The water wall is the same as the mass and Trombe wall systems except that contained water replaces the solid wall. Since water has a greater heat capacity per unit volume than brick or concrete and because of the convection currents within the water cause it to act almost as an isothermal heat store

72 Indirect Gain Systems: Water Wall

73 Water Wall Waterwall modules by One Design Inc Thermal curtain with water tube storage by Kallwall corporation Hand Operated insulating shutter with water drum thermal storage by Zomeworks corporation

74 Indirect Gain Systems: Roof Pond Thermal mass, generally in the form of waterbeds is placed horizontally, above the ceiling of a building. This mass is exposed to direct solar gain, heats up and transmits this heat by conduction to the ceiling below which will then transmit these heat by radiation and some convection to the space below. At night and when the sky is overcast, insulation covers the warmed water and reduces the heat loss to the exterior.

75 Indirect Gain Systems: Roof Pond

76 Isolated Gain Systems: Sunspace There is an attached sunspace that consists of a glazed enclosure built to the south side of a building. Depending on the climate and how the sunspace is used, there may be a heat storage wall separating the sunspace from the building or other storage that serves to stabilize the temperature. Vents and shading can also help to avoid overheating if necessary.

77 Isolated Gain Systems: Sunspace