Gusting winds – definitely not ideal testing conditions if you want repeatable, accurate results. If you find your before and after air leakage tests don’t make sense, strong baseline pressures are a likely cause.
In response to the questions regarding fixing common gauge issues and before and after leakage tests articles.
Wind speed is really not the issue, wind fluctuation is. Changes in wind speed and direction will cause the pressure in the building to change during a test. Since often waiting for a calm day to reduce this effect is not an option, here are some ideas to combat those gusts.
1st Consider Your Standard
Wind speed is occasionally required to be measured for certain testing protocols. In most cases, it is simply estimated, so that differences in results during retest can be explained.
Some standards may require you to reschedule your test for better conditions.
2nd Increase Time Averaging During Baseline Pressure Test
Some standards refer to bias pressure as “zero flow pressure difference”, “offset pressure difference”, or "bias pressure".
If it is windy, or there are high baseline pressure variations, increase the time averaging period of this baseline pressure reading. Also, increase the averaging period of induced building pressure readings.
3rd If your Locations Are Usually Windy, Find a Method to Shield the Wind – Or, Invest in a Wind Damping Kit
These kits help to minimize the effect of wind on an exterior reference pressure tube.
Alternatives for those who only deal with mild - moderate wind, or infrequent windy conditions is to put your reference tube in your fan box (OUTSIDE of course). This will shield the wind, and the large space is unlikely to have too much of its own pressure to affect results.
4th Finally, Remember to TEST IN BOTH DIRECTIONS to Even Further Reduce the Effects of Baseline Pressures, Such as Wind.
Testing in both directions will eliminate errors because the baseline value now affects results very little since it tends to cancel - What gets added onto the test in one direction is subtracted from the test in the other.
* A good rule of thumb is to take 30 baseline readings at least 5 seconds apart and if they vary more than 1.5 Pa, increase time averaging until they are less than 1.5 Pa. Then take your induced pressure readings for ten times longer than your baseline time averaging and you'll have super accurate results.
Got a question or comment? Leave it below and we’ll get back to you, and possibly feature it in an article.