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Passive Heating and Cooling

Passive Heating and Cooling

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Passive Heating and Cooling

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Presentation Transcript

  1. Passive Heating and Cooling

  2. Passive Design • Uses ambient energy sources instead of purchased energy • Daylighting • Natural ventilation • Solar energy

  3. Active Design • Uses purchased energy to keep the building comfortable • HVAC • Heat pumps • Radiant panels • Chilled beams • Electrical lights

  4. Hybrid Systems • Use some mechanical energy to enhance ambient energy • Heat recovery ventilation • Economizer ventilation • Solar thermal systems • Radiant facades • Ground source heat pumps

  5. Optimize design for passive strategies first • Downsizes the active systems you’ll need

  6. Building Massing • Massing is the overall shape and size of the building • Can be one of the most important factors in thermal comfort and daylighting

  7. Massing • Take advantage of site conditions • Rainwater harvesting • Avoid shading wild lands • Massing for visual comfort • Some general strategies for using massing to maximize daylight energy and comfort • Difficult to get consistent daylight and control glare from east and west windows • Side of the building facing the sun’s path can generally be easily shaded

  8. Massing • Generally buildings longer on their east west axis are better for daylighting and visual comfort

  9. Massing • Using skylights can improve the daylighting in single story buildings regardless • Single stories aren’t the best for land use • Larger and taller buildings should have thinner profiles to help maximize daylighting from windows • Can also improve daylighting by having a central courtyard or atria or other cutouts • Increase the height of each story

  10. Massing for Thermal Comfort • Often helped by extending the east-west axis to take advantage of the consistent sun on northern/southern exposures • But thinner buildings may not be better

  11. Thin/Tall Buildings • Increase the surface area to volume ratio • Makes utilizing natural ventilation for passive cooling easy • Tall buildings increase effective ventilation because wind speeds are faster at greater height • Increases cross ventilation and stack effect ventilation

  12. Thin/Tall Buildings • Rules of thumb from 2 scenarios with windows facing the direction of the prevailing wind • For spaces with windows on only one side, natural ventilation will not reach farther than 2x the floor space to the ceiling height into the building • For spaces with windows on opposite sides, the natural ventilation effectiveness limit will be less than 5x the floor to ceiling height into the building

  13. When planning urban centers, specifically in the heating dominated climates, having buildings gradually increase in height will minimize high speed winds at the pedestrian level

  14. Solar Radiation & Heat Transfer • Thin and tall buildings also increase the exposed area for heat transfer through the envelope • In cold climates, massing that minimizes the ratio of surface area to volume can avoid unwanted heat loss • The sun’s heat is advantageous and the surface area facing it helps passively heat the building • Side of the building exposed to the sun can be increased while reducing the exposed areas of the other sides

  15. In hot climates thin buildings with their biggest face exposed to the sun • Cause unwanted solar gain, use shading devices and good windows • Taller buildings can reduce unwanted gains • Suns heat strikes stronger on the roof than the walls in warm latitudes

  16. Sun’s heat and light do not come from all directions equally • Windows facing away from the sun’s path get diffuse light, but without heat gain (have heat loss too) • Windows facing east are warmed in the morning when the • Windows facing west are warmed in the afternoon when spaces are generally warm

  17. Building Program • Sparsely populated buildings with little activity or equipment have little heat from internal loads • In cold climates you can benefit from a compact floor plan • Minimizes ratio of surface area to volume

  18. Roofs can be angled for optimal solar heating • Reveals and overhangs can shade parts of a building with other parts of the same building • Aerodynamic curves can reduce heat loss from infiltration • Interior buffer zones can be replaced in a building’s west side to protect living and working areas from hot afternoon sun (stairs, restrooms, entry corridors)