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: 259

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

Videos

  • Add Videos
  • View All

Twitter

Latest Activity

tedkidd replied to Rob Madden, Solar Home Broker's discussion Indoor Air Quality Monitors and Meters
"Yep, steep price but you will learn a lot. We are hoping these new devices that homeowners can own…"
42 minutes ago
tedkidd replied to Luis Hernandez's discussion ERV Configuration
"We don't recommend ERV's anymore. If you are in a green grass climate ventilating…"
54 minutes ago
Home Energy Magazine's blog post was featured

Is the Perfect Wall Realistic?

Wrong question. The right…See More
1 hour ago
Chris Laumer-Giddens's blog post was featured

Building with Rocks, Rocks. Check out the Drying Potential

Building with Rocks, Rocks! Check out the Drying Potential.Check this out! This 24" x 48" x 2"…See More
1 hour ago
Dan McKee posted a blog post

Innovations for Heating and Cooling

Heating and cooling of indoor spaces is one of the major operations of modern households and…See More
6 hours ago
Amber Vignieri posted a status
"In the market for a #solar home? We're bringing you improved solar #MLS listings. http://bit.ly/2auldQ8"
yesterday
Tom White's video was featured

CalCERTS Plenum Pressure Matching

This video describes how to perform plenum pressure matching to measure system airflow.
yesterday
Rob Madden, Solar Home Broker replied to Rob Madden, Solar Home Broker's discussion Indoor Air Quality Monitors and Meters
"Awesome respnose...thanks for your insight!"
yesterday

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service