Skip to content NREL Buildings Research National Renewable Energy Laboratory (NREL)
Field Test Best Practices: A Resource for Practical Residential Building Science

Main menu

Wind Speed and Direction

Wind primarily affects the infiltration in a house, so measuring wind speed and direction in a field test is particularly important if natural infiltration is being measured. Tracer gas tests, for instance, are very sensitive to outdoor conditions and wind speed should always be measured when tracer gas tests are performed. Wind speed is measured using an anemometer, pictured below. Wind direction is typically measured separately by a wind vane or weather vane. Wind direction is not always measured in past field tests, even if wind speed is measured.

Photo of a three-cup anemometer shows a metal rod with a rotating top portion, from which three concave metal cup shapes sprout evenly in all directions. At the bottom is a wire that sends the wind speed reading down to the computer console (not pictured).Photo of a weather vane shows a mounted base from which a cylindrical, rotating component sits. Attached to the rotating piece is a small end shaped similar to a bullet, with a large, tail similar to that of a plane.

Three-cup anemometer at a field test site
Lieko Earle

A weather vane for measuring wind direction
Saperaud, Wikimedia Commons

The cup-type anemometer, as pictured, directly measures wind speed by measuring the rotational speed of the cups. The three cup anemometer is the most common configuration for cup-type anemometers, since it responds more quickly to large gusts than four cup anemometers. Weather vanes are designed to rotate freely on the vertical axis so they can respond to small changes in wind direction. The weight on either side of the vertical axis is equal, but the surface area is much larger on one side. That side will catch the wind if the pointer is not pointing directly in line with the wind. Weather vanes typically send the wind direction to a data logger using a potentiometer; as the vane rotates, the resistance of a potentiometer changes.