Passive Solar Design

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Passive Solar Design
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Passive solar has been used for thousands of
yearsSouthwest United States
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Adobe solar architecture
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Passive Solar Design

• Passive solar heating is defined as using solar
  energy striking windows, skylights, greenhouses,
  clerestories, and mass walls in order to provide
  heating for a house.
• Generally, such solar collection occurs
  passively, without the extensive use of pumps or
  fans typically used in active solar collector
  systems.
• Because heating is needed only over the colder
  part of the year (Sept. to May), passive solar
  design must also eliminate unwanted solar heat
  gains during the summer.
• The use of techniques to eliminate solar gains
  and to cool a house with the use of active
  systems is often referred to as passive cooling

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General Rules
1. Conservation Levels Higher than normal levels
of insulation and airtightness 2. Distribution of
Solar Glazing distributed throughout the
building proportional to the heat loss of each
zone 3. Orientation Optimum within 5 degrees of
true south 4. Glazing Tilt Looking for
perpendicular to sun angle in winter, although
vertical efficient where lots of reflective snow
cover 5. Number of glazing layers 3 to 4 for
severe climates, less otherwise 6. Night
insulation and Low-E glazing Greatly improves
reduction of night heat losses 7. Mixing passive
systems can increase comfort levels.
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Types of Passive Systems

• Direct Gain
• Trombe Wall or Mass Wall
• Sunspace or Greenhouse
• Roof Systems

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Direct Gain Systems

• Sunlight incident on transparent surfaces allows
  the energy to enter the living space directly and
  is called Direct Gain.
• South facing windows thus form the basis for the
  simplest type of solar heating system.
• With some simple guidelines, this design is the
  cheapest and best way to incorporate solar into a
  house.

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Direct Gain Passive Solar Design

• Surfaces should be generally facing south (to
  within 20 degrees)
• Overhangs should prevent unwanted summer gains (2
  ft typical at 40 degrees latitude)
• Window area should be 8-12 of the house floor
  area if no extra thermal mass is added
• This amount of passive solar gain should provide
  no more than 40-50 of the yearly heating load
• More area may be possible if additional thermal
  mass is added.

• PRECAUTIONS
• Excess window area can result in a loss of
  privacy, too much glare, underheating and
  overheating
• Movable insulation should be designed to be easy
  to install and use

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A Simple Direct Gain System
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Direct Gain Rules

1. Mass Distribution spread it around evenly 6
   times glazing area (3X minimum)
2. Mass Thickness thin and spread out better than
   thick. More than 4 for masonry or concrete not
   useful
3. Colour Floors dark to absorb more heat, walls
   and ceilings lighter to reflect light.
4. Surface Covering insulative coverings (ie. Rugs)
   greatly decrease performance of thermal mass
5. Concrete Block Masonry If used, a high density
   with cores filled with grout

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Direct Gain Rules, cont'd

1. Floor Materials Concrete or brick preferred. If
   insulating under, at least 4 thick (100mm). More
   than 6 (150mm) not useful.
2. Limits on Direct Gain Glazing Area South facing
   glazing limited to prevent large temperature
   swings. 7 of floor area for low mass buildings,
   13 of floor area for high mass buildings.
3. Glazing orientation Vertical facing due south
   preferred. Vertical easiest to build, and easiest
   to shade in summer. Performance penalty for
   15degrees off due south is 10 and for 30 degrees
   is 20 loss so within 15 degrees recommended.
4. Night insulation Really helpful but can be very
   costly.
5. Thermal Insulation Insulation located OUTSIDE
   the thermal mass.

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Good design is based on combining several
elements and ideas

• Knowledge of seasonal changes in sun path
• Landscaping in the site plan
• Overhangs
• Appropriate use of thermal mass
• Energy efficient design for the thermal envelope

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The Suns Seasonal PathThis path is hemisphere
and latitude dependent
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40 Degree Latitude Sun Chartshowing altitude and
azimuth angles for different months of the year
and times of the day
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Site PlanDont shade the south, except for
overhangs, but do shade the east and west sides.
Decks, porches and carports also may be used to
shade.
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Overhangs on the South Side
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Thermal Massprovided by normal drywall and
furnishings and also by slabs, mass walls,
fireplaces, etc.
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Clerestory is also direct gain

• Excellent for bringing daylighting to northern
  spaces (deep houses)
• Can use north wall masonry heat storage
• Overhang over clerestory window shades in summer

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Example of Clerestory House
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Thermal Storage Walls or Trombe Walls

• Advantages
• Eliminates glare
• Lowers temperature swings in room
• Vents allow partition of energy into daytime and
  nighttime heating
• Sun hits entire mass

• Precautions
• More expensive and less efficient than direct
  gain
• More difficult to reduce nighttime losses
• Best for sunnier climates
• Occupies valuable space in building

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Trombe Wall with Vents
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Operation of Trombe Wall

• Sunlight hits the darkened mass wall and absorbed
  heat moves slowly across the wall
• The inside surface temperature peaks 6-8 hours
  after the midday outside surface peak
• Operational vents allow optional controlled air
  circulation into the space during the day
• Overhang reduces wall sun exposure during the
  warmer months
• Vent added to outside at the top can drive warm
  air out in the summer and bring cooler air from a
  north vent
• can be used as part of a south-facing greenhouse
• may be retrofitted to existing houses with brick
  or stone construction

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SUNSPACE CONCEPTwith mass wall added
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What is a Sunspace??
Sunspace -- a passive solar heating system type
consisting of a glassed-in room like a
greenhouse, atrium or conservatory, located on
the south side of a building and separated from
other building spaces by a common wall. Common
Wall -- a wall separating a sunspace from other
living spaces. Greenhouse -- a sunspace used
primarily for growing plants Projected Glazing
Area -- net glazing projected onto a single
vertical wall.
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Attached Greenhouses or Sunspaces

• Advantages
• Lower temperature swings in adjacent living space
• Flexible can be operated in many modes
• Provides additional living or growing space
• Works well in late winter and spring when
  standard overhangs block direct gain through
  windows

• Precautions
• Price moderate to high
• Thermal performance depends greatly on how it is
  operated

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Sunspace Rules

• Effect of orientation optimum due south.
  Penalties about 5 for 30degrees off due south.
  More summer overheating for off south directions.
• Use of Mass increases spaces livability.
  Reduces overheating. Optimum thickness for
  masonry walls between 8 and 12.
• Area of Mass direct gain rules apply 3mass to
  1glazing.
• Do not glaze end walls for both summer and
  winter performance.
• Summer Venting needs to be vented during summer
  especially if not well shaded.
• Wall Colour Direct gain rules apply, except
• a. use darker colours in general as light
  colours tend to reflect light and heat out of
  the space
• b. if used as a green house, surfaces in corners
  need to be light to improve plant
  performance/life.

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Sunspace Rules, cont'd

• Sunspace width 15 to 20 feet works well.
• Colour dark colours work better to absorb heat.
• Plants and other lightweight objects Limit.
• Roof Need to be able to shade it in the summer
  to avoid overheating. Curtain, awnings or
  internal shades, OK.
• Common Wall Needs to be able to be closed off
  from main living space to avoid overheating.
  Preferably masonry (like trombe wall).
• Common wall vents required as one of the ways
  heat is transferred to the living space.
• a. doorways, 15 of glazing area
• b. window openings, 20 of glazing area
• c. high and low vent pairs, 10 of glazing area

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Solar Greenhouse with thermal mass in the floor
and in water barrels
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Thermal Storage Roofs

• Advantages
• Provides both heating and cooling
• Provides low temperature swing in the building
• Can provide 100 of heating and cooling in milder
  climates

• Precautions
• Structural support for heavy mass expensive
• Most easily used in 1 story buildings
• Typically 50 size of floor area
• Least acceptable design in earthquake prone areas

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Thermal Roof Concept
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Passive Solar Design Style

• The effectiveness of solar heating does not
  depend on the style (Cape Cod, Colonial, modern,
  contemporary) of house that you design.
• Houses may be small and simple, or spectacular
  the solar concept being applied is the same.
• Of course, the smaller the house, the less
  resources and cost will be needed to build and
  maintain it.

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High Mass Adobe House
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Earthship
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Earthship
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Earthship
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Earthshiphttp//earthship.com/
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Direct Gain Solar House
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High Mass Desert House
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Adobe Sunspace High Mass House
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Clerestory Direct Gain House
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Point House in California Coast
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Direct Gain Solar House