When doing a blower door test, do you ever use long term average? Why or why not?

Digital pressure and flow gauges have an option for time averaging, such as 1, 5 or 10 seconds, long term or a manual time average option.

Under what circumstances would you use the long term average and why?

Views: 243

Reply to This

Replies to This Discussion

When the wind is breezy, I use long term averaging. The more the pressure jumps around due to breezes, the longer the term that I use. Even then, I mentally average the readings. This is after I have taken steps to shield the end of the outside hose from the wind.

Wind is caused by a difference in air pressure so the change in air pressure from the wind, or a passing truck, is reflected in the change in the readings of a digital pressure gauge. Keep in mind that 1 pascal is a tiny change of pressure. I find that the best way to get a stable baseline is to insert a "T" fitting into the reference tube and connect 2 reference tubes. Place 1 tube on 1 side of the house and the other tube on the opposite side of the house. Be sure that the tube nearest the blower door is at least 5' (preferably more) from the fan. If the fan needs to be installed where it is blowing into an enclosed porch or mud room (not a good choice unless there is no better alternative) make sure the tube is outside of the porch.

Hi Kim,

Wind is probably the most frequent reason for using the time averaging with our manometers, but there is another that we need to be careful with.  Manometers are unique in that they ignore barometric pressures.  Place your refer tube out the front door and walk your manometer (long tube) upstairs or into the basement and even though the top to bottom pressure may vary (on a cold day) by 50 pascals or more our manometers will register very little.  When the temperature of our tubes and the air inside is the same as in the house, any changes in elevation are canceled out.  However, if those tubes just came out of an ice cold vehicle, or a hot one, and have not fully acclimated, our readings will drift.  In this case, before we start averaging we need to allow those tubes to become room temperature.  The section of tube that goes outside needs to acclimate as well.

Bud

I never use any setting but "long term" average. Any other setting will always give you a less accurate average reading. Under the "long term" setting the manometer automatically calculates a mathematically continuous average. That means that you can "hold " the reading after "any" length of time and it will give the average for all of the seconds that you had the meter running.

RSS

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network.

Latest Activity

Rick Karg replied to Carly@AirCycler's discussion The (Small) Cost of Ventilation Without Recovery
"As a member of the ASHRAE 62.2 committee (and president of Residential Energy Dynamics, the author…"
Friday
Bradford E. White replied to Elizabeth Guinn's discussion ERV in need of backflow preventer.
"I would use an in-line backdraft damper such as Artis Industries or the ones made by Fantech and…"
Thursday
Kim Tanner posted a video

Wireless Air Leakage Testing

This webinar will discuss the use of WiFi technology to conduct and document blower door and duct leakage tests for compliance with local energy codes. The s...
Thursday
Profile IconPerry Grossman, Daniel Pate and Ottawa Furnace Filters joined Home Energy Pros
Thursday
Kirsten Richnavsky added a discussion to the group Building Performance Institute (BPI)
Thumbnail

Breaking the link between unhealthy homes and unhealthy kids

Listen in on IAQ Radio to a discussion on reducing the household triggers that cause asthmaattacks…See More
Thursday
Kirsten Richnavsky posted a discussion

Breaking the link between unhealthy homes and unhealthy kids

Listen in on IAQ Radio to a discussion on reducing the household triggers that cause asthmaattacks…See More
Thursday
Kim Tanner posted events
Thursday
Ottawa Furnace Filters posted a blog post

Some Useful Information about Furnace Air Filters

There is not much we can do about the air pollution outside of a house in Ottawa, Canada, but we…See More
Thursday

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service