Building Pressurization in Extreme Cold Climates

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by H. Ed Bargar, P.E., Instructor; Department of Mechanical Engineering, University of Alaska Fairbanks, Duckering 337, 306 Tanana Loop, Fairbanks, AK 99775-5905,,
Debendra K. Das, P.E., Ph.D., Professor; Department of Mechanical Engineering, University of Alaska Fairbanks, Duckering 337, 306 Tanana Loop, Fairbanks, AK 99775-5905,,

Document Type: Proceeding Paper

Part of: Cold Regions Engineering: Cold Regions Impacts on Transportation and Infrastructure

Abstract: Building pressurization, the differential pressure between the interior of a building and its exterior surroundings, is an important design consideration. Pressurization is the driving force in building infiltration/exfiltration. It also affects air flow within building zones. Improper calculation of pressurization can result in undersizing the building's heating and cooling systems, improper operation of air distribution systems, improper operation of elevators, and freezing and failure of water distribution and circulation systems. Building pressurization is affected by several environmental and design considerations. Primary environmental influences are: wind speed/direction and exterior-to-interior temperature difference. Pressurization due to these two parameters is generally referred to as wind effect and buoyancy or stack effect respectively. In extreme cold climates, the predominant effect is of the buoyancy type. This effect is caused by the temperature, and thus air density, differences between the interior of the building and its exterior surroundings. The larger the temperature difference, the larger the buoyancy effect. In extreme cold climates, large temperature differences often occur at times when wind speed is negligible. Also of critical importance is that while wind effect is transitory, lasting from minutes to hours; extreme temperature differences can be persistent, lasting days, weeks, or longer. The American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) presents an idealized equation to calculate the buoyancy effect. This paper compares differential pressure measurements from an actual building to this idealized model. It also presents several new statistical models based on the collected data. These new models should provide engineers with improved tools to properly account for building pressurization for designs in extreme cold climates.

Subject Headings: Cold regions | Building design | Cold region construction | Buoyancy | Temperature effects | HVAC | Water circulation | Air flow |

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