All Posted on July, 2014

New Proposal has HERS Raters Gasping for Air

Friday, July 25th, 2014

New Proposal has HERS Raters Gasping for Air

A recent proposal for a new RESNET ANSI Standard on air leakage testing may have some raters gasping for air. Most of the proposed ANSI standard is already in effect, but some of the changes in tolerance levels could P1200129cause some back and forth, especially for duct leakage to outside testing. Ready for some stair climbing? Make sure you’ve got plenty of oxygen reserves for this one. You just might need them with the proposed changes in the pipeline (especially at our altitude around the Mile High City).

There is a new ‘duct leakage to outside procedure’ found in section 4.4.2 of the draft proposal for the Draft RESNET ANSI Standard for air leakage testing. It is actually titled…take a deep breath…”Standard BSR/RESNET 380- 20xx PDS-1 Standard for Testing Air Leakage of Building Enclosures, Air Leakage of Heating and Cooling Air Distribution Systems, and Airflow of Mechanical Ventilation Systems,” and breathe.

Jeez, and I thought I was long winded!

Title aside, one of the changes in the proposed standard that has real impact is that it requires more back and forth to the blower door and duct leakage tester to verify that conditions in the pressure readings at each fan haven’t changed during the process. Makes sense, and we should be doing that. However my concern is that the tolerance levels of a half Pascal (0.5) are too strict.

We’ll get back to the 0 tolerance issue, but first let’s see what a normal setup looks like with the current standard. I’ve organize the list by the number of trips up and down the stairs.

  1. 1)  Set up blower door
  2. 2)  If zoned system open zone dampers and turn off air handler at power switch or breaker—stairs
    1. a)  Remove filter
    2. b)  Could hook up the duct tester at this point and be sure to also cover inlet of fan for baseline (to save a set of stairs)
  3. 3)  Take your reference hose with you and plug into nearby supply
    1. a)  Start sealing the ducts (assumed to be on the same level of supply reference)—
  4. 4)  Baseline the blower door with door opening sealed
    1. a)  Remove cover
    2. b)  Induce 25 pa pressure in house wro
  5. 5)  Go back to duct tester
    1. a)  Unseal cover
    2. b)  Induce pressure in ducts to 0 pa wrh (+/- 0.5 pa)
    3. c)  Record reading
  6. 6)  Go back to blower door and adjust if need be (proposed change in standard says if it is not in the 24.5 to 25.5 range, adjust to be within range)
  7. 7)  Go back to duct tester and adjust to 0 pa (since the house pressure may have impacted duct pressure)—push “hold” on the device and get reading*

*This assumes a single system for a multistory home (basement serving 1st floor or attic system serving 2nd floor) where the duct tester is not on the same level as the blower door

Currently all of the steps above must be followed in accordance with Chapter 8 of the RESNET Standard. However, there is a slight change in adding a pa tolerance in the proposed ANSI Standard which could have a major impact. If the proposal goes through at the 0.5 pa tolerance, I think it might be worthwhile to purchase a wireless control for your device. It may not save a ton of stair running on those calm days, but on gusty days it might be worth investing in, if only to have more real time readings and adjustments to meet this tolerance. Alternatively, having cruise control abilities on your device may be better than no auto controls at all, however on an extremely gusty day all the ups and downs in checking and adjusting the readings would still be necessary. Even with cruise control the controls are rarely a perfectly tuned 0.5 pa. Time averaging is necessary as well and may help in the process too.

All of this assumes you have a 2nd gauge and I know many of us do not. If you don’t already have a 2nd gauge, this setup is going to be even more challenging and take more time, which translates to more costs. (It may nooxygen pleaset even possible with some gauge base line functions). In this case you may need to weigh out the time it takes to unplug your one gauge and go back and forth while doing baseline math in your head. In this analysis you should consider how much a new gauge costs. It may be worth it and some might find it could pay for itself over time (wireless setups including the gauge run from $1000 to $1500). Of course, you’ll need to consider the additional maintenance/calibration costs in having an additional gauge in this equation.

Back to the tolerance issue, to put this into perspective let me draw from a recent example. Just the other day I was running a Tectite blower door test on a gusty day. Winds weren’t terribly gusty—10 to 20 mph. I wasn’t able to get a reading with a tolerance set at 2 pa. That’s 4 x the level of tolerance of the 0.5 pa being proposed for house and duct pressures. If the computer software could not get a reading at the 2 pa range, how we can expect a human to get a 0.5 pa range on the duct leakage even on those days we see slight gusts? Concerning, eh?  The RESNET ANSI Committee needs to provide some data to justify this strict of a range and ultimately find a better sweet spot between accuracy and tolerance. Something closer to 2 pa seems reasonable, but I suspect even 1 pa could be much improved and save a lot of headache on getting it just right! I’ve proposed 3 pa as I think that’s as good a number as throwing out a 0.5.

In short, with the proposed tolerance of 0.5 pa for house pressure, you may never find that sweet spot of 25 and 0 respectively, without some real time data on the house and duct pressures at the same time. Ultimately, having wireless readings may save a rater and their builder a re-inspect on those very windy days if you can more quickly adjust each of the fans on the fly to find the sweet spot. I’m not confident that we can expect wireless technology to save us on this one and I believe a wider tolerance needs to be considered. EnergyLogic was the only company who commented on this particular point (see #74) and believes that the ANSI Committee is reasonable enough to reconsider this sticking point.

Forgive my “long winded” rant (pun intended). I just want to save raters time, money and most importantly save some painful joints from all the stair running. If you have other experiences to share, some data to provide, or just want to rant please do so in our comments section below or email us at

Glenn PeaseGlenn Pease
Technical Director
EnergyLogic, Inc.