Rethinking the Computer Enhanced Design Process

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Thermal Analysis
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Weather analysis
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Solar exposure
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Heat flow

• Heat will flow from a hot substance to a cold
  substance.
• Heat can flow in three ways
• Conduction
• Convection
• Radiation

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Heat flow

• Conduction

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Heat flow

• Convection

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Heat flow

• Radiation

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Heat flow in buildings

• There are six main types of heat loss/gain
• Fabric gains
• Indirect solar gains
• Direct solar gains
• Ventilation Gains
• Internal Gains
• Inter-zonal gains

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Thermal analysis

• Thermal analysis in Ecotect

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Thermal analysis

• Types of thermal calculation

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Modelling with zones

• A number of properties can be set for each zone

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Psychrometric Chart

• Graphical representation of the condition of the
  air
• Relates temperature and humidity
• Each point on the graph represent one type of air

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Psychrometric Chart
ABSOLUTE HUMIDITY (or vapour pressure)
TEMPERATURE
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Psychrometric Chart

• Properties of air
• Dry-bulb temperature
• Absolute humidity (or vapour pressure)
• Dew point
• Relative humidity
• Wet-bulb temperature

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Psychrometric Chart

• Dry-bulb temperature
• Temperature of the air
• oC or oK
• Measured with standard thermometer

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Psychrometric Chart

• Absolute humidity (or vapour pressure)
• The amount of water vapour in the air
• Vapour pressure results from water vapour in the
  air

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Psychrometric Chart

• Dew point
• For a particular temperature, there is maximum
  amount of water vapour
• The dew point is when the air can not hold any
  more water vapour
• The air is saturated

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Psychrometric Chart

• Relative humidity
• The amount of water vapour compared in the
  aircompared to the maximum that the air can hold
• Measured as a percentage
• RH of 80

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Psychrometric Chart

• Wet-bulb temperature
• For a given temperature, dry air will feel cooler
  than humid air
• Lower humidity increases evaporation
• Evaporation produces a cooling effect
• The wet bulb temperature tries to take this into
  account
• The wet bulb temperature is always a bit lower
  that the dry bulb temperature
• The higher the humidity, thesmaller the
  difference

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Psychrometric Chart
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Human comfort

• Human comfort is very subjective. It depends on
• Air factors
• Dry bulb temperature
• Relative humidity
• Environmental factors
• Air movement
• Mean Radiant temperature
• Personal factors
• Activity (metabolic rate)
• Clothing

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Human comfort

• Environmental factors Air movement
• 0.3 m/s Barley noticeable
• 0.5 m/s Pleasant breeze
• 0.7 m/s Light breeze
• The effect of air movement depends on
  temperature
• In warm conditions, air movement is a comfort
  (increases heat loss)
• In cold conditions, air movement is a discomfort
  (feels draughty)

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Human comfort

• Environmental factors Mean Radiant temperature
  (MRT)
• Hot and cold object greatly affect our perception
  of temperature
• Hot objects emit radiant energy to our body
• Cold objects absorb radiant energy from our body
• Mean Radiant Temperature is
• the average of all the radiant energy reaching
  our body
• It is positive if surrounding objects are warmer
  than our body
• It is negative if surrounding objects are cooler
  than our body

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Human comfort

• Personal factors Activity (metabolic rate)
• What are you doing?
• Death 0 Met 0 W/m2
• Seated 1 Met 46 W/m2
• Standing 1.2 Met 70 W/m2
• Walking 2 Met 116 W/m2
• Sport 4 Met 235 W/m2
• Exertion 7 Met 405 W/m2

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Human comfort

• Personal factors Clothing
• What are you wearing?
• Naked 0 Clo
• Work suit 1.0 Clo

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Human comfort

• Prediction of human comfort
• A mathematical model is required to predict
  comfort
• Three commonly used models
• Thermal neutrality
• Adaptive comfort
• Predicted mean vote

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Location Data
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Solar Position
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Solar Position
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Solar Position
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Solar Position
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Psychrometry
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Psychrometry
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Psychrometry
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Psychrometry
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Psychrometry
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Wind Analysis
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Wind Analysis
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Hourly Data
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Hourly Data
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Weekly Data
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Weekly Data
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Monthly Data
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Monthly Data
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The sky

• From the solar radiation that arrives from the
  sun
• About 25 is absorbed and scattered by air
  molecules
• About 25 is reflected back out to space
  (affected by clouds)
• About 50 arrives at the surface
• Some of this is reflected back again (affected by
  ground cover, e.g. snow)
• The entire sky dome emits light due to
• Scattering by air molecules
• Scattering by suspended particulates
• Reflection by moisture vapour and clouds.

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The sky

• Solar radiation can be broken down into two
  parts
• Direct solar radiation direct from the sun
• Diffuse solar radiation from the sky dome

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Simple model
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Time Period Single day
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Time Period
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Time Period Average Daily
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Time Period Total Monthly
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Time Period Full Hourly
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Radiation Data
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Radiation data

• Received - Displays the amount of radiation
  actually incident upon selected surfaces.
• Available - Displays the total amount of
  radiation actually available from the sun over
  the same period.
• Reflected - Displays only the amount of solar
  radiation reflected off solar reflectors onto
  selected surfaces.
• Shading - Only a single point is tested at the
  centre of each object.

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East facing
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West facing
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South facing
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North facing
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