Energy Efficiency Experts

• Here is the definition from Building Science website.
  http://www.buildingscience.com/glossary/stackeffect
  

  Air movement caused by warmer air rising and cold air falling. This generates small but steady pressures in direct relation to the size of the temperature difference and the height of the column of air. The resulting pressure differences can lead to air leakage and generate unplanned air flows within buildings that result in indoor air quality problems.
  

  The stack effect is not something we eliminate. We can however understand it and reduce its effect. There are even ways to use to our advantage.
  

  Understanding it
  

  Air is a buoyant fluid. Temperature changes the density or buoyancy of air. Our homes are usually a different temperature than the outside air. In the winter we heat our homes. The warm inside air is less dense or lighter than the cool outside air. This air then moves toward top or ceiling of the house. If there are pathways in the ceiling the conditioned air will escape.
  As the stack effect increases the neutral plane within a home rises.

  The stack effect is strongest when there are holes in the bottom of the house and the top of the house. This will create the bottom of the home to be under negative pressure and the top of our home under positive pressure.  The negative pressure zone under the neutral plane is creating air infiltration. The positive pressure zone above the neutral plan is creating exfiltration. This causes a super highway of conditioned air loss.
  

  This process can be reversed in the cooling season. With the denser cold air falling the high areas pull hot air from the attic and releasing cold airat the bottom of the home to the outside.
  

  The stack effect happens because of temperature difference and how that difference changes the buoyancy of air. It is constant and happening in your home right now.
  

  Reducing its effect
  

  Let’s talk about the solution. It is easy to understand and fairly short. By performing whole house air sealing we reduce its effect. By paying close attention to our high and low holes we remove the path the stack effect is traveling. By reducing the stack effect and moving our home into neutral pressure or slightly positive we lower the plane of negative pressure caused by the stack effect. (See does my house suck)
  

  Using it to our advantage
  

  The passive soar home takes in account the stack effect and uses it during the warm season for cooling. Drawing air low from the home and exhausting high from the house creating a natural breeze way to cool the home. By opening lower and upper windows in a home we can also take advantage of the stack effect to flush warmer air out. The whole house fan works on this principal with mechanical ventilation increasing its effect.

  With our mild climate in San Diego does the stack effect matter?

  Since energy costs money and we codition our space the answer is yes. By using it to our advantage we can reduce the amount our systems are working

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