Week 6 - Urban microclimate and site planning Flashcards
What is the urban microclimate scale?
- Urban canopy layer & urban boundary layer
- Urban microclimate happens with the canopy layer where people live and work
- Affecte people’s qaulity of life
What are some factors that influence the urban microclimate?
- Urban setting (size, density, materials, form, devlopment)
- City metabolism (resource use, waste, etc.)
- City location (climate, topography, surroundings)
- Weather (temp, wind, solar, rain)
- Temporal setting (day/nightime, season)
What is the Thermal Sensation Index (TSI)?
- Air temperature
- Horizontal solar radiation
- Wind speed
- Relative humidity
- Mean radiant temperature
Goes from - cold to nuetral to hot
What are some urban microclimate design strategies?
Wind——————————-
- Site planning
- Building design
Thermal Radiation ———————-
- Less direct solar
- Less surface temperature
Temperature ———————
- Increase evaporative cooling
- Reduce heat accumulation or release
Precipitation ————————–
- Rain protection
How can ventilation be improved with site planning and why is it important?
- Breezeways between dense structures
- Roads and open spaces –> manipulate layout to increase flow, arrange buildings to channel wind
- Building seperation and vary height
Importance———————————- - Can cause “downdraft effect”
- Or upwards deflection – increasing wind pressure and speed
- Redirects wind
How can ventilation be improved with building design and why is it important?
- Increase building permeability (give them HOLES) –> for example, sky gardens or reducing ground coverage
- Reduce building squareness
How can surface temperature be reduced?
- Use cool materials with high solar reflectance
- Green wall
- Increase albedo – design stuff that’s light-colored
How can evaporative cooling be increased?
- Vaporization helps it cool off
- Water features
- Green wall
- Creening to increase evapotranspiration
- Use permeable paving
How can heat accumulation be reduced?
- Increase ventilation in open spaces
- Do not build buildings that obstruct downhill wind flow
- Allow sea breeze by building small buildings
How can heat dissipation be reduced?
- Vehicles, exhaust outlets, building materials are sources that release heat –> put them away from pedestrian open spaces
- Reduce thermal mass heat storage of building materials
Case studies of effective microclimate design:
- Kai Ching Estate (green spaces, space between buildings, air corrdors)
——–Hong Kong Science Park (align with wind corridors, lanscape adaptation, high reflective solar index) - Choi Hing Court (from report)
- Long Ching Estate (building permeability, good ventilation)
———-Siu Sai Wan Complex (innovative, connects open spaces, wind corridors, shading)
——–Hysan Place (innovative design, sky gardens, building permeability)
——- Zero Carbon building (permeable paving, shading, greenery)
What is the AVA?
- Air Ventilation Assessment
- Wind Velocity Ratio (VR) - indicator of wind performance
- How much wind is available and is actually enjoyable (taking into account buildings, topography, etc)
- VR is measured as Vp/Vi (V pedestrian/V infinity)
- Vi captures wind velocity where its best (not urban effected)
- Measured against what its like at the pedestrian level
- High ratio = less impact
What are some air ventilation assessment tools?
- Computational Fluid Dynamics (Autodesk Vasari Wind Tunnel and Wind Simulation in Urban Planning) – initial studies
- Wind Tunnel Modelling (Wind tunnel test for buildings) – initial and detailed studies
- Reported in 16 directions
- Initial study: less directions is allowed
- Detailed study: no simplication is allowed
- Also assesses surrounding area
What are the test points of the air ventilation assessment?
- Where wind is recorded
- Resultant wind can be assessed
- Three types of test points ————–
- Perimeter: project site boundary, assess immediate effect, also location on junctions of roads, main entrances, and corners of project site
- Overall: evenly distributed at open spaces, on streets, and places of project
- Special: areas that specific problems may appear – assesses additional info
What are some case studies related to wind ventilation?
- Kai Tak Development - discovery of wind velocity ratio for urban planning
- ## Publlic Housing Development - discovery of WVR
