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: 241

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.

Latest Activity

Paul Raymer's blog post was featured

What does it take to be a certified Home Energy Professional Quality Control Inspector (HEP QCI)?

A quality control program requires knowing a lot about a lot of different subjects.  A HEP (BPI…See More
9 hours ago
Bryan Pringle replied to Bryan Pringle's discussion Dense packed cellulose in basement?
"Can you tell me more about how the plastic makes the moisture worse?   I understand that in…"
11 hours ago
Profile IconMatthew Cooke, yasmine smith, myacand heat and 2 more joined Home Energy Pros
12 hours ago
Bryan Pringle replied to Bryan Pringle's discussion Dense packed cellulose in basement?
"I like cellulose because of its air leakage reduction property and the ease of making a quality…"
12 hours ago
Bryan Pringle replied to Bryan Pringle's discussion Dense packed cellulose in basement?
"This example is the reverse of my suggestion.  I would do high end vapor barrier against…"
12 hours ago
Al Heath replied to Bryan Pringle's discussion Dense packed cellulose in basement?
"Really?  Go back and read these posts again.... "play ground for mold."  I…"
12 hours ago
Mary Desilva posted blog posts
12 hours ago
Kim Tanner posted a video

Single Family Residential Air Leakage Testing

This session will cover the basics of air leakage testing on a single family home as well as issues that affect the accuracy and repeatability of the test. T...
13 hours ago

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service