Module 18 - Passive solar.pptx

STRAND Energy-Star Training Passive solar Design and Inspection © 2023 STRAND Dallas I Texas 972 620 8204 Elements of Passive Solar Design To design a completely passive solar home, you need to incorporate the five elements of passive solar design: © 2023 STRAND Dallas I Texas 972 620 8204...

STRAND Energy-Star Training Passive solar Design and Inspection © 2023 STRAND Dallas I Texas 972 620 8204 Elements of Passive Solar Design To design a completely passive solar home, you need to incorporate the five elements of passive solar design: © 2023 STRAND Dallas I Texas 972 620 8204 © 2023 STRAND Dallas I Texas 972 620 8204 1. Aperture (Windows) – Windows should face within 30 degrees of true south, and during winter months they should not be shaded from 9 a.m. to 3 p.m. The windows in living areas should face south, while the windows in bedrooms should face north. In colder climates, reduce the window area on north-, east-, and westfacing walls, while still allowing for adequate daylight. In warmer climates, use north-facing windows along with generously shaded south-facing windows. When purchasing windows, look for ENERGY STAR®qualified windows. © 2023 STRAND Dallas I Texas 972 620 8204 Absorber – The hard, darkened surface of the storage element is the absorber. This surface – such as a masonry wall, floor, or partition – sits in the direct path of sunlight. Sunlight hits the surface and is absorbed as heat. © 2023 STRAND Dallas I Texas 972 620 8204 Thermal Mass – Floors and walls that absorb heat are particularly useful for naturally heating homes in colder climates. Thermal mass refers to materials that retain or store the heat produced by sunlight. The difference between the absorber and thermal mass, although they often form the same wall or floor, is that the absorber is an exposed surface whereas thermal mass is the material below or behind that surface. © 2023 STRAND Dallas I Texas 972 620 8204 Heat Distribution – Passive solar design allows solar heat to circulate from collection and storage points to different areas of the house. A strictly passive design will rely on natural heat transfer, but some applications use fans, ducts, and blowers to help distribute heat. © 2023 STRAND Dallas I Texas 972 620 8204 Control – Elements such as roof overhangs or trees can be used to shade the window during summer months. Other elements for controlling temperature include electronic sensing devices, such as differential thermostats that signal a fan to turn on, vents and dampers that allow or restrict heat flow, low-emissivity (low-e) blinds, and awnings. © 2023 STRAND Dallas I Texas 972 620 8204 How Passive Solar Heats and Cools Understanding how passive solar home design works also means understanding how heat moves and how it can be stored. Heat moves from warmer materials to cooler ones until there is no longer a temperature difference between the two. Thus, passive solar design lets heat flow through the house from warmer areas to cooler areas by using the following heat-movement and heat-storage mechanisms: © 2023 STRAND Dallas I Texas 972 620 8204 Convection. Warmer gases and liquids will rise, while cooler liquids and gases will sink. In a house, warm air rises because it is lighter than cold air, which sinks. This explains why warmer air accumulates on the second floor of a house, while the basement stays cool. Some passive solar homes use air convection to carry solar heat from a south wall into interior spaces © 2023 STRAND Dallas I Texas 972 620 8204 Radiation. Heat can radiate and move through the air from warmer objects to cooler ones. To design for warmer weather, passive solar design can incorporate light-colored materials to reflect incoming solar heat and radiate heat off a building. To design for colder weather, homeowners can use darker materials to absorb the sun’s heat and radiate it into the home. Clear glass, which transmits nearly 90% of the sun’s heat, can also be incorporated to radiate the heat into a home’s interior – like a greenhouse © 2023 STRAND Dallas I Texas 972 620 8204 Heat capacity. Passive solar design takes advantage of many different materials capable of storing heat. Masonry materials like concrete, stones, brick, and tile are commonly used as thermal mass in passive solar homes, especially in floors and walls https://www.energy.gov/energysaver/energy-saver © 2023 STRAND Dallas I Texas 972 620 8204 A solar direct gain system can reduce heating, cooling, and lighting energy requirements through proper sizing, placement, orientation, and/or control of windows, skylights, shading devices, and solar storage mass within the building. To determine aperture area, measure width and height of south-facing glazing and indicate tilt angle. Note glass type(s) (e.g., double glazing) and presence of night insulation (if any). Determine orientation with a compass reading (adjusted for magnetic deviation). Determine the type of thermal mass, its thickness and dimensions. Determine if the mass will be lit by direct solar rays between the hours of 9:00 a.m. and 3:00 p.m. during the winter. Note any trees or other obstructions to solar gain. © 2023 STRAND Dallas I Texas 972 620 8204 Thermal mass systems consist of solar-exposed heavyweight materials with high heat capacitance and relatively high conductance (high thermal diffusivity) such as masonry, brick, concrete, tile, stone, or water placed in the same zones(s) as the solar collection area(s). These elements may be integral with the building or distinct elements within the building. Distinct components: Trombe wall -uses a heat storage mass placed between the glass and the space to be heated. Measure area of storage mass, determine material, thickness, and capacitance. Water wall -replaces the existing wall, or parts of it, with containers that hold water. © 2023 STRAND Dallas I Texas 972 620 8204 Thermosiphon air panel (TAP) -has one or more glazing layers of glass or plastic, an air space, an absorber, another air space, and (often) an insulated backing. These are similar in appearance to active flat-plate collectors, often mounted vertically on walls, or groundmounted, so that the living space is higher than the collector to facilitate convection from the TAP to the house. See Greenhouse, above, for specific inspection items. © 2023 STRAND Dallas I Texas 972 620 8204