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Barometric Pressure

Barometric Pressure

Barometric pressure is used in detailed psychrometric calculations and in calculation of the density of air, and can be important in accurate determination of heat transport via airflow. Barometric pressure is by definition an absolute pressure measurement. Alternatives to direct measurement of local barometric pressure include:

  • Obtaining weather data from a nearby weather station
  • Using a fixed value for barometric pressure (adjusted if needed for elevation)

Barometric pressure values reported by weather stations are altitude adjusted (i.e., corrected to the pressure that would be observed if the station were at sea level).

The resolution of barometric pressure transducer output can be increased by selecting models with ranges corresponding to expected atmospheric pressure. The table below provides guidance on pressure range selection.

In Building America field tests, barometric pressure is usually calculated from the test site elevation, using the following equation:

P = Px (1-(Lxh)/T0)^(gM/RL)

Table—Approximate minimum and maximum expected local atmospheric pressure at varying elevations
Elevation (ft)Approx. minimum expected local atmospheric pressure (psi)Approx. maximum expected local atmospheric pressure (psi)
Sea level14.215.2
2,00013.214.2
4,00012.213.2
6,00011.312.2
8,00010.511.3
10,0009.710.5

Extreme conditions, especially those created by hurricanes and typhoons, can generate pressures well outside these ranges. The lowest (sea level) pressure ever recorded was about 12.62 psi, and the highest about 15.84 psi.

Application Notes

  • For most building-related measurements, the specific location of a barometric pressure transducer in or near a building isn't important. The fractional change in absolute air pressure is roughly 0.3 percent for a 100 foot elevation change.
  • Barometric pressure transducers are typically not sensitive to orientation.