The principles of air movement and The Stackalator

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The principles of air movement and The
Stackalator
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Heat Transfer

• Convection
• Convection is the transfer of heat by
  circulation or movement of the heated parts of a
  liquid or a gas.
• Requires a fluid medium (gas or liquid).
• Caused by density differences between warmer and
  cooler parts of a fluid medium (warm air rises,
  while denser, cooler air falls).

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Principles of Air Movement

• Air moves from high pressure to low pressure.
• Air follows the path of least resistance.

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Warm Air Rises

• Warm air is less dense than cool air so it tends
  to rise above cool air.
• Warm air rising is the driving force behind
  convection.
• This dynamic is always at work in a house.

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Convection Currents in Your Home

• Air cools and sinks as it travels across room

• Warm air rises from register

Window

• Cool air circulates back towards register

Register
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Signs of Heat Loss
If you see this
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Insulation
You might find this
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Cause of Heat Loss
Or this
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Air Barrier
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Air Sealing

• Air sealing reduces heat flow from air movement
  and prevents water vapor from entering the wall.
• Air sealing and moisture control make insulation
  more effective.
• Insulation does not stop air flow.

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Air Sealing Materials

• Some examples of air sealing material
• Drywall
• Plywood
• Oriented Strand Board (OSB)
• Stucco
• Cardboard
• Any rigid board insulation
• Air barriers must be properly installed and
  sealed at the joints with caulk or other
  appropriate material.

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Building Airflow Simulation

• In this activity, youll learn about
• Air movement in buildings
• At what locations air sealing is most effective

On the diagram, use arrows to show what happens
at each hole when smoke is directed towards it.
Add notes below. ________________________________
__________________________________________________
________________________________
Top Closed 5 Open 4 Open 3 Open 2 Open 1
Open _____________________________________________
__________________________________________________
___________________
5 4 3 2 1
5 4 3 2 1
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Stack Effect

• Occurs when a building is heated, and the warm
  air inside the building is less dense than the
  colder air outside.

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The taller the building, the stronger the stack
effect
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Heat Transfer Review
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