Passive Solar Design

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Ever wondered why some homes feel more comfortable than others? Want to re-discover what our ancestors knew about home building that works in concord with site, climate and orientation? Want to visit a honest-to-goodness passive solar home? Join us as we investigate the concepts and practice of passive solar buildings. Whether you're building new, remodeling or want to improve the energy and comfort performance of your home, this workshop is for you.

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Passive Solar Design

  1. 1. Passive Solar Design: Make that beautiful home feel BeautifulCCSE Presentation, Copyright 2011 1
  2. 2. Where we want to goProvide you with the concepts, background, resources and motivation to integrate passive solar design into your homes—both existing and future. 2
  3. 3. Roadmap• What is passive solar? – Recalling what we forgot• Why we should do this? – It’s not just about saving $• Passive solar fundamentals – Eating low on the food chain – 14 principles of passive solar design• Understanding thermal mass• Some simulations – SketchUp visualization – Overhang design• Real world examples and applications – How to “solar-passivate” existing buildings – How to build the ideal passive solar house CCSE Presentation, Copyright 2011 3
  4. 4. What is Passive Solar?Natural Conditioning“The art and science of heating, cooling, lighting and ventilating a building without outside fuels.”• Passive solar heating• Passive cooling• Daylighting• Cooling by natural ventilation CCSE Presentation, Copyright 2011 4
  5. 5. Recalling what we knew• Anasazi understood these principles – The Anasazi Indians built stone and mud dwellings in the deeply carved canyons of the desert Southwest dating back to 12th century BCE. – Nestled into south-facing canyon walls under natural overhangs, their homes were sheltered from the intense summer sun. – Yet as winter approached, the low- angled sunlight dropped below the overhang to provide warmth. CCSE Presentation, Copyright 2011 5
  6. 6. Recalling what we knewThe Greek city Olynthus – The ancient Greeks utilized solar energy to heat their homes. They understood the value of sunlight so well they treated solar access as a legal right. – The Greek city of Olynthus was laid out so that homes would have unfettered access to the sun—5th century BCE CCSE Presentation, Copyright 2011 6
  7. 7. Where is this “technology” today? “All streets trend east-west and all lots are oriented north-south. This orientation (which has become standard practice in Davis and elsewhere) helps the houses with passive solar designs make full use of the suns energy.” Village Homes, Davis CAhttp://www.villagehomesdavis.org/home 7
  8. 8. From the sun to us…free• The sun delivers to us, free of charge, 300 BTU/sf (88W/sf) of clean, green energy every hour. 8
  9. 9. Making a friend of the sunThis is about 176 kWh to the average house, every hour, every day it’s sunny. – The key question is: Friend? 9
  10. 10. Making a friend of the sun Or foe? 10
  11. 11. So why do we continue building these? North 11
  12. 12. So why are we not building solar-integrated passive homes today? • It’s too expensive. • It’s too complicated. • Energy is too cheap so why bother. • Inconvenient. • We will lose jobs, hurt the economy. • Fear—loss of control. • What else? ? CCSE Presentation, Copyright 2011 12
  13. 13. Benefits• Americans spend about $54 billion each year heating and cooling their homes (ignoring the externalized cost of energy—extraction, distribution, pollution, climate disruption, etc.) – Passive design can cut this cost significantly, and that’s just the beginning. 13
  14. 14. Benefits…• Natural conditioning (as opposed to air conditioning) is – Simple (no moving parts) CCSE Presentation, Copyright 2011 14
  15. 15. Benefits…Elegant (based on physics and natural laws— biomimickry) • Designs that follow natural laws tend to be more successful over the long term. 15
  16. 16. Benefits…– More efficient: • Using energy with minimal conversions is fundamentally more efficient (compare electric heater vs. solar heating) – By the time we use it, electricity from coal is 15% efficient 16
  17. 17. Benefits…Natural conditioning (as opposed to air conditioning) is – More comfortable (radiant heating rather than forced air, etc.) • Quiet, solid construction, warm in winter, cool in summer, gradual temperature variations 17
  18. 18. Benefits…– Attractive: • Large windows, sunny, daylit interiors, open floor plans– Results in a healthier house (indoor air quality is higher since we’re not circulating pollutants) 18
  19. 19. Benefits…– Lower life cycle cost • increased economic security with rising energy costs • In our “moderate” climate zone, utility bills of $300-$500 per month in the summer and $150-$250 in winter are common and will go up. 19
  20. 20. Benefits… – High level of owner satisfaction with increased resale value – Green (environmentally sound)• A quality home need not begreen• But a green home must behigh quality. 20
  21. 21. PatternsAll acts of building, no matter how large or small, are based on rules of thumb developed through years human experience. We call these rules of thumb “patterns.” * 21*Ed Mazria, Christopher Alexander
  22. 22. PatternsFor example, a pattern that helps us decide how much load a horizontal building member can bear: 20 feet 2 x 10 joist 22
  23. 23. Patterns“Each pattern is connected to other patterns which relate to it. Every pattern is independent, yet it needs other patterns to help make it more complete.”*We call this approach by other names, such as integrated or systems- based building. 23*Ed Mazria
  24. 24. PatternsThe fourteen patterns of passive solar design can be summarized thus: 1. Harvest solar heat by proper building orientation with respect to the site and annual solar path. 2. Keep that heat in the building by proper air sealing and insulation (quality envelope). 3. Store the heat (and level temperature variations in both seasons) with properly designed interior thermal mass. 4. Use efficient backup heat for long overcast spells and imperfect designs. 24
  25. 25. Pattern 1Choose a site with good solar exposure CCSE Presentation, Copyright 2011 25
  26. 26. Pattern 1On our site, we had to take down some eucalyptus trees and plant lower canopy trees. • This provided both sun and food. 26
  27. 27. Pattern 1• The sun reaches higher in the sky in summer than in winter. – This is the altitude angle. June 22 March 21 December 22 27
  28. 28. Pattern 1The sun rises further northward in the summer than in the winter. – This is the bearing angle, summer: CCSE Presentation, Copyright 2011 28
  29. 29. Pattern 1The sun rises further northward in the summer than in the winter. – This is the bearing angle, winter: 29
  30. 30. Pattern 1A Solar Pathfinder knows all this and will determine where the shadows fall throughout the year. CCSE Presentation, Copyright 2011 30
  31. 31. Pattern 2Orient the long--east-west axis of a house--within 10 degrees of true south – Solar gain vs. degrees deviation from true south, by rotation angle A: • 0° 100% • 22° 92% • 45° 70% • 67° 36% A South 31
  32. 32. Pattern 2…• In warm climates, more than 10-degree deviation may cause summer overheating, especially late in the day.• “Choosing a good building shape and orientation are two of the most critical elements of an integrated design.” – Sustainable Buildings Industry Council 32
  33. 33. Pattern 3Locate most windows on the south side of a house – “The right amount” of south facing glass is the solar collection system. • Use the Goldilocks Principle 33
  34. 34. Pattern 3…• Locate most windows on the south side of a house – At the lowest solar altitude (winter solstice) the sun can penetrate 20 ft into a house. – With “proper” overhangs, solar collection diminishes in summer (higher solar altitude). • Courtesy of the solar control system. CCSE Presentation, Copyright 2011 34
  35. 35. Pattern 3…• Locate most windows on the south side of a house 35
  36. 36. Pattern 4Minimize windows on the north, west, and east sides and “tune” them to the orientation – Too much glazing on east and west walls causes summer overheating. – Too much glazing on north walls results in excessive heat loss. 36
  37. 37. Pattern 4…– In general, we want to tune our windows thus: • South: – High solar heat gain coefficient (SHGC), >0.5 • East, west: – Low solar heat gain coefficient (SHGC), <0.4 • All exposures: – Low U-factor (<0.4) to minimize heat loss (best insulation) – Low-e glass for best overall performance both seasons 37
  38. 38. Pattern 5 Provide overhangs and shading to regulate solar gain – For additional shading on east and west walls, use exterior window shading. – Vertical trellis or long horizontal trellis can reduce western, late afternoon sun. 38http://www.susdesign.com/overhang/
  39. 39. Pattern 5…• Provide overhangs and shading to regulate solar gainOverhang calculatedfor 32 degrees northlatitude Energy10 model CCSE Presentation, Copyright 2011 39
  40. 40. Pattern 5 For San Diego, January 22, noon. 40http://www.susdesign.com/overhang/
  41. 41. Pattern 5 For San Diego, June 22, noon. 41http://www.susdesign.com/overhang/
  42. 42. Pattern 5…Provide overhangs and shading to regulate solar gain – Use interior color selection that brings solar heat and daylight deep into the interior – Choose roof and wall colors and reflective indices that reduce heat gain. See http://www.coolroofs.org/ 42
  43. 43. Pattern 5…Provide overhangs and shading to regulate solar gain – Solar-integrated landscaping • West and east side evergreen trees – Summer cooling and winter heating (cut wind) • South side deciduous trees • Minimize heat-generating hardscapes and heat island CCSE Presentation, Copyright 2011 43
  44. 44. Pattern 5…• Landscaping: nature provides smart shading Shades in summer Mulberry in winter CCSE Presentation, Copyright 2011 44
  45. 45. Pattern 5…• Un-shaded south facing glazing needs awnings or overhangs. CCSE Presentation, Copyright 2011 45
  46. 46. Pattern 5…Jacaranda now cools the home in summer when west facing rooms would overheat. CCSE Presentation, Copyright 2011 46
  47. 47. Pattern 6Provide sufficient, properly situated thermal mass – This is the critical element that deserves special attention – “The basic strategy is to design the house so that its own masses—mainly walls and floors—are so placed, proportioned, and surfaced that they will receive and store a large measure of incoming solar energy during the daylight hours and will gently release this stored heat to the house interior during the night hours or cloudy days.” --Peter Van Dresser, Passive Solar House Basics CCSE Presentation, Copyright 2011 47
  48. 48. Pattern 6…• Provide sufficient, properly situated thermal mass Free or Incidental mass • The parts of the home’s structure or décor that absorb thermal energy—act as thermal mass. Examples are: • drywall • framing lumber • doors • furniture 48
  49. 49. Pattern 6…• Provide sufficient, properly situated thermal mass Sunlit mass or direct mass • Mass placed directly in the path of incoming solar radiation. Examples are: • tile or masonry in the path of sunlight • fireplace surround in the path of sunlight • exposed slab floor in the path of sunlight 49
  50. 50. Pattern 6…• Provide sufficient, properly situated thermal mass Indirect mass • Mass not accessible by incoming solar radiation. Examples are: • tile or masonry not in the path of sunlight • fireplace surround not in the path of sunlight • exposed slab floor not in the path of sunlight • walls not in the path of sunlight CCSE Presentation, Copyright 2011 50
  51. 51. Pattern 6• Provide sufficient, properly situated thermal mass – The higher the density, the higher the heat storing capacity up to about 4” thick. Material Density (lbs/ft3) Sheetrock 145 Concrete 140 Concrete block 130 Clay brick 120 Lightweight concrete block 110 Adobe 100 CCSE Presentation, Copyright 51 2011
  52. 52. Pattern 6…Putting this all together… Using the pattern that 7% of solar glazing balances with the incidental thermal mass, We use the following spreadsheet to determine the solar glazing-to-thermal mass balance… CCSE Presentation, Copyright 2011 52
  53. 53. Pattern 6… South- Direct Indirect facing Solar glazing Solar glazing sunlit Indirect floorTotal floor glass, Gs area Gs needed area Gs mass wall mass mass area (sf) (sf) (sf) available (sf) Remainder (+/-) (1: 5.5) (1: 8.3) (1:40) Amount Gs Need needed 7% more? (sf) + thermal 2000 240 140 240 mass 100 550 830 4,000 2500 175 175 175 --- 0 0 0 0 + thermal 3000 345 210 345 mass 135 743 1121 5400 53
  54. 54. Pattern 6… Summary of solar glazing-to-mass balance: – Take 7% of total floor area. – If your south facing glazing is more than this, take the difference and add correct ratios of thermal mass to store the additional solar gain. 1:40 1:8.31:5.5 CCSE Presentation, Copyright 2011 54
  55. 55. Pattern 6• Provide sufficient, properly situated thermal mass – “Light-colored walls nearest solar glazing reflect light onto dark- colored thermal mass located deeper within the structure to ensure greater and more even distribution of heat.” – Daniel Chiras CCSE Presentation, Copyright 2011 55
  56. 56. Pattern 7Insulate walls, ceilings, floors foundations and windows – In other words, build a quality envelope with minimal • uncontrolled conduction • infiltration • radiant gain. 56
  57. 57. Pattern 7…Insulate walls, ceilings, floors foundations and windows 57
  58. 58. Pattern 7…Insulate walls, ceilings, floors foundations and windows CCSE Presentation, Copyright 2011 58
  59. 59. Pattern 7…Insulate walls, ceilings, floors foundations and windows 59
  60. 60. Pattern 8Quality water barrier to protect insulation from moisture 60
  61. 61. Pattern 8Quality water barrier to protect insulation from moisture 61
  62. 62. Pattern 9Air barrier: seal the envelope, especially attic penetrations: 62
  63. 63. Pattern 9Air barrier: much harder to control indoor temperatures with a leaky building. 63
  64. 64. Pattern 10Design thin: each room should be heated--directly or indirectly--by solar heat 64
  65. 65. Pattern 11Avoid sun drenching: create sun-free spaces 65
  66. 66. Pattern 12Back up heating: provide efficient, properly sized, environmentally responsible back-up heating. – Tight ducts, etc. 66
  67. 67. Pattern 13Protect homes from winds by landscaping or earth sheltering CCSE Presentation, Copyright 2011 67
  68. 68. Pattern 14Synchronize daily living with daily and annual cycles. 68
  69. 69. Let’s apply what we’ve learned…Which of these is apassive solar design? 69
  70. 70. Let’s apply what we’ve learned…South elevation 70
  71. 71. South elevation… 71
  72. 72. Concrete block building, west elevation… 72
  73. 73. Crawl space…bottom of the “thermal envelope” 73
  74. 74. This home has a new, 84% efficiency furnace 74
  75. 75. This attic and subfloor space 75
  76. 76. Waterproofing high performance windows 76
  77. 77. Summary1. Harvest solar heat by proper building orientation with respect to the site and annual solar path.2. Keep that heat in the building by proper air sealing and insulation (quality envelope).3. Store the heat (and level temperature variations in both seasons) with properly designed interior thermal mass.4. Use efficient backup heat for long overcast spells and imperfect designs.5. At the very least, build quality. CCSE Presentation, Copyright 2011 77
  78. 78. Top it off with renewable energy 78
  79. 79. Questions?CCSE Presentation, Copyright 2011 79
  80. 80. References and AcknowledgementsThe Solar House: Passive Heating and Cooling, Daniel Chiras.The Passive Solar Energy Book, Edward Mazria, Rodale Press, 1979.The Passive Solar House, James KachadorianGreen From the Ground Up, David JohnstonNatural Remodeling for the Not-So-Green House, Carol Venolia & Kelly LernerThe Not So Big House, Sarah SusankaYour Green Home, Alex WilsonThe Timeless Way of Building, Christopher AlexanderThe Ecology of Commerce, Paul HawkenOverhang calculator: http://www.susdesign.com/overhang/Energy-10: Sustainable Building Industries Council (not currently supported)http://www.villagehomesdavis.org/homehttp://www.coolroofs.org/ 80
  81. 81. Today’s Engineers• Estimates of energy savings resulting from the application of passive solar design concepts are provided by: – ASHRAE (1984) – DOE (1980/1982) – LBL (1981) – Ed Mazria, architect and sustainability authority (1979)• “Passive solar heating, cooling and lighting design must consider the building envelope and its orientation, the thermal storage mass, and window configuration and design.” – From ASHRAE Handbook –HVAC Applications 2007, Ch. 33. CCSE Presentation, Copyright 2011 81
  82. 82. Notes:Photos of fruit and nuts.Simi’s houseCool roof rating council link CCSE Presentation, Copyright 2011 82
  83. 83. Patterns 83*Ed Mazria, Christopher Alexander

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