Wind speeds and pressures
Wind speeds have a dramatic effect on the requirements of windows. It is necessary to know the wind speed at the local position of the window to estimate the local pressure applied to the window and to verify if the window will withstand the requirements for air and water resistance.
The Beaufort scale was introduced in 1806 by Admiral Sir Francis Beaufort of the British Navy to describe the wind effects on a fully rigged man-of-war at sea. It has now been extended to cover the effects of various wind speeds on land objects. The Beaufort scale is useful because it gives us a physical picture of the various wind speeds. As a scale each Beaufort number covers a range of wind speeds because it is designed for estimates only.
Wind speed (knots)
0 Calm 0-1 knots
Smoke rises vertically.
1 Light Air 1-3 knots
Smoke shows the direction of the wind.
2 Light Breeze 4-6 knots
Wind is felt on the face and leaves rustle in the trees.
3 - 7-10 knots -
4 Moderate Breeze 11-16 knots
Loose paper blows around and whitecaps seen on water.
5 - 17-21 knots -
6 Strong Breeze 22-27 knots
Wind whistling in telephone wires and spray on water.
7 Moderate Gale 28-33 knots
Large trees sway.
8 Fresh Gale 34-40 knots
Twigs break from trees.
9 Strong Gale 41-47 knots
Branches break from trees.
10 Whole Gale 48-55 knots
11 Storm 56-63 knots
12 Hurricane 64 knots and higher
Structural damage on land and storm waves at sea.
1 knot = 1 nautical mile/hour = 1.85 km/hour = 1.15 mile/hour
Conversion from any given wind speed to another wind speeds is relatively easy. This is not the case when attempting to convert from a wind speed to a wind pressure. Wind pressure is affected by many local features and whilst a rough conversion is possible it is not published here because of the uncertainty.
Last edited: 11/03/10
© Tangram Technology Ltd. 1998
Our standard disclaimer regarding Internet data applies.