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Duct Testing

I joined the 4 ring club today with the tightness in a duct system.

848 sf apartment. 15 CFM at 25 leakage to the outside. They still have to seal the attic plane and a few other places. I will be back for finals on this one. The HVAC got it right on this phase of duplexes. 18 months ago we had some leakage to the outside in 150 CFM at 25 range. One unit had 120% of system air flow leakage total.

Any one else have a 4 ring success story.


  • Ed MinchEd Minch Posts: 112
    This is an excellent number, but reflects mostly good shell tightening - if the ducts are inside the "envelope" of the apartment. What was the total leakage? We have had total leakage of a 2-1/2 ton duct system with no AHU in a 2200 ft2 single family at 18 CFM25. Very very good work on the part of the HVAC contractor, but quite rare.
  • Ed
    Ducts in the Attic on this one. That is why I was in early. Before attic insulation. The enclosure came in at 8+ ACH at 50. The total duct leakage was not very good. A good part of the total might have been my set up. This contractor had to redo the 1st phase, so he is trying to do it right on the second phase. The will do the air sealing and fix the one large hole I found. That will make my return trip worth while.
  • Ed MinchEd Minch Posts: 112
    It is hard to get those small apartments down to a low ACH, but you might want to address that part of the job before you address more duct issues. The only duct item I might look at is getting those ducts inside perhaps through the use of enclosed soffits.
  • Ed, I met with the builder and the architect in February 2014. I didn't get the ducts inside. I also didn't get a ducted mini-split.

    Ultimately, 16 of the 46 are slabs, so most will be in conditioned space. The first phase was coming in with smaller units 738 sf between 3.5 and 4.5 ACH at 50. If these do, they will have a HERS between 75 and 80. The lender requires 80 or lower. We aren''t doing the fix it after we failed stuff.
  • Stan KuhnStan Kuhn Posts: 170
    If all of the ducts are in the attic I would think the total and "to outside" would be the same.
  • Not necessarily. If you have a filter slot, in the return plenum inside, would create total leakage, but not outside. If there is leakage between the grill and the ceiling, that would be in total. You are not supposed to seal the grill to the ceiling with mask. And, I was doing a preliminary test. My set up may have contributed also to the total. My primary interest was Leakage to the outside and seeing where the enclosure was.
  • Well, I dunno. I just did a 4200ft2 home with 22 duct runs (three floors/zones). We decided to do the test at the TESP, given that's kind of close to how the system operates (push and pull on the fan)... My sub blew the static budget and it came in at 125pa TESP. So, we ran it up and found 40cfm @125pa. Didn't take pictures, don't really care, as long as the system performs.

    One thing of interest, the watt draw on the ECM fan was 10 times the face plate rating at the higher static. I gave the contractor a choice; ease the constrictions and meet the static budget or pay for the excess energy the ECM fan used over the 15 year life of the equipment. He ponied up a check for $3000 for excess fan energy... just saying...
  • Oh yeah, 9 tons in two systems to start. did the whole house with 2 stage 4 ton operating at 2.5 with four tons of air. not perfect but we were pretty pleased and the home is within 3 degrees F anywhere you go.
  • David ButlerDavid Butler Posts: 3,889
    @Timothy, what was your static budget? 125PA = 0.5 IWC, which is higher than I typically specify for TESP budget, but shouldn't push an ECM to "10 times face plate rating" (you mean AHU faceplate or motor faceplate?).

    BTW, 40 CFM @ 125 PA is impressive, but it's not at all close to how the system operates. TESP represents the highest static the blower sees. Static at the grilles is 0, so the average pressure the duct system sees is somewhere in between. ASHRAE 152 goes into details on why 25PA is reasonable for testing, although any duct pressurization test will necessarily overstate leaks at the ends and understate leaks close to the blower.
  • Sorry..
    Senior moment. Static budget was around .6 wc or so (just don't have the file with me to confirm now). TESP came in at 1.25.
    yeah I know about the reasons why 25 Pascal is supposed to be good but if we're measuring just performance, why don't we measure it closer to the way it operates. and I do understand tesp is not an exact measurement of how the ECM fan exerts energy but it sure keeps the HVAC guy in line if he's gotta pay for amps over the face plate ratings. ECM gets sold for their efficiency, but nobody talks about how much energy they expend when the static is over budget
  • Ed MinchEd Minch Posts: 112
    I am amazed your HVAC contractor would agree to such a charge. Did you have a prior agreement with him?
  • I gave the hVAC guy a choice: open up the trunk (going through a floor) to get the static down or indemnify the client for the extra cost his mistake would cost the client. He chose to pay... he couldn't avoid the fact that his installation wasn't going to perform to spec which included airflow, duct leakage and TESP to name a few and so he wasn't going to get paid unless he acknowledged the situation.
    performance specs are written into the contract and we commission every job. HVAC should be using equipment to measure to insure they meet the specs. it's amazing how many I n our industry think just cause they install an ECM fan it's going to save energy... increased resistance makes these puppies work harder. I think John Proctor did some good research on this. It might be on his website.
    David, I'm sorry to be so vague. The medical experience I told you about at Hot/Dry conference kicks in and the detail just becomes elusive without the file. We read the fan watt draw as it ran and compared it. I can't remember whether the number came from the AHU or the motor face plate...
  • I routinely test 2 ton units with total leakage in the 20's. I thought the 4-ring club was for systems with less than 10 CFM of leakage and always referred to total leakage. Leakage to the exterior isn't a good measure of how tight the ducts are. To me, leakage to the exterior will tell you about where the leakage might be and if you missed any register in the home, not about how tight the ducts are, in my opinion.
  • Using a certain size ring only indicates the total air flow through the unit. Since the more accurate readings are using the smallest diameter opening on the fan, then using a four ring to measure 20 cfm is more accurate than using a 3 ring. The 3 will go to 20 according to the manual, but no lower. So using the four has an accuracy advantage. Let's see what happens when I go back and conduct the final test.

    BTW: I am questioning my set up, because the walls had not been cleaned. My duct mask picked up a fine layer of dust. I think the adhesive was impaired by the dust. Next time I tape to drywall, I will wipe it down.
  • Stan KuhnStan Kuhn Posts: 170
    It's the "Ring 4 Club", and we don't count, it's only for the HVAC folks.John, I have gotten pretty good at putting the mask inside the boot, so going onto metal & sticks bettter, but sometimes also needs wiped off, dirt & oil. I have one ring 4 guy, it's nice to work with those who try to do it right.
  • Stan, I agree that working with guys that get it is great. Especially since he was a no ring guy on the last project.
  • In my area, Lehigh Valley PA, some Building Code jurisdictions require 3rd party duct testing, others do not. One of my contractor clients (Climate Specialists Inc.) has all their installs tested, required or not. Most of their projects include two or three HVAC systems and have TOTAL measurable system leakage rates in the low twenties. Example: 5400 Sq Ft house, three systems , two systems are not registering (flashing LOW) at 100 Pa and the other system is reading 23CFM@25PA. Their worst project leakage recently was a two system home with TOTAL leakage in the sixties. One system flashing low @100Pa and the second system testing 63 Pa@25CFM. I pulled the equipment and we were removing duct sealing tape and found we had not sealed a kick space supply upstairs during testing. When I offered to reset and test with all the supply and returns sealed he said "It meets Code, we know the ducts are OK. See you on the next job."

    Regrettably this company is the exception. A lot of the contractors just pass the Code requirement. Frequently some rework is required to pass and sometimes we end up having to put in smoke to show the contractor why their ducting is not passing.
  • Ed MinchEd Minch Posts: 112
    I believe that as long as you get the ducts inside a well sealed envelope, it does not matter that you have extreme tightness in the ducts. I would rather spend my builder's money on the envelope.

  • Ed I used to be in that same school of thought. But once we started doing Areoseal in addition to addressing the envelope I saw what a tremendous difference it made in the comfort of the home. Homeowners were blown away by the additional comfort increase that getting air to its intended location made. I've had a few clients that only wanted the Areoseal because they had saw the Hometime special. More than one has been told us they have been able to turn the thermostat back several degrees!
  • Nice...Ring 4 club.. Impressive....
  • don jdon j Posts: 27
    Adding to the envelope thought what kind of envelope are you using to need 3 systems in a 5400 sq ft house. We are doing that in Northern MN with loads in 35-40 k btu range then it makes the HVAC really shine. training our builders to seal up our sips I have 4 ratings this year by independent raters at .30 ACH 50 or less We call them the D ring club on the building side
  • I had my 1,130sf house duct work sealed internally (Aeroseal), all in the attic externally insulated hard pipe from 1979, and went from 65cfm to 9cfm losses at 25. The airhandler was taped and sealed externally. The increased air flow was felt and heard immediately. It's only been five months so we're still collecting the utility data. The cleaning and sealing took a day. It was $800 total.
  • Hey @David. I just looked at what I wrote and see why you were asking about the increased fan watt draw. The total TESP on test out wasn't 125pa, it was 1.25wc = 312pa.
    The point I was alluding to is as follows; the "Fourth Ring Club" is a great way for people to learn that they really can seal up a system tightly when the common belief is that it's just not cost effective (which is just old resistant thinking) or worse yet that if the leakage is "inside conditioned space" that's somehow OK, when it's the delivered air to specific living space that counts when comfort and efficiency are at stake...
    BUT, for Fourth Ring club to really mean anything to performance, there's more to look at than just tight ducts, for instance; are they sized/installed correctly? how hard do they make the ECM fan work? are temperatures equal room to room? what is the throw and volume of the registers being used to create adequate mixing (thus equal temperatures)? to mention a few of the more important ones for the distribution system.
    In California, where designers tout our Title 24 building code "as being the most advanced in the nation", the average performance of installed HVAC systems is 60% of design/equipment rating. That's 7200 btu's actual, out of every 12,000 promised to be delivered (and I'm not begging a discussion about sensible versus latent here, this is across the board heating and cooling with cooling being somewhat worse). "Gosh, I buy more efficient equipment and for some reason it costs me the same or more to run" says many a consumer.
    My point? having tight ducts is admirable only if they are sized and installed correctly and then, only a required component of a truly great system.
  • For those of you that are "Auditors" and not installation people, you really do count! this is not just an HVAC thing. You need to understand this stuff well enough to offer your clients performance specifications to be written into the contract that can be measured and verified on test out that prove the system is performing to design. If auditing is not tied inextricably to end result, you are not doing anyone a favor by telling them what you think can be achieved and then not making sure it actually is... we're all in this together toward a sustainable, healthy systemic end result. please consider; we're all a team doing a systemic job and we better start making the rubber hit the road in that regard.
  • Good discussion here on tight ducts and the ring4club. From inception, it has existed as a way to recognize excellence for Home Performance companies that pay careful attention to HVAC performance factors while assembling extremely airtight ducted distribution systems ("LO" using ring 3 on DuctBlaster) . As the founder, I welcome any questions or comments about it, and if there is interest in expanding it to include additional categories, I'm all ears. There's no money in this, apart from the generosity of The Energy Conservatory who pays the site hosting and domain name fees. For more info, check out the website at ring4club.com and download a membership application on the Contact page. Oh, and if ring 4 club is too easy, there's now a Ring 5 Club too ("Low" when using ring 4) with just one company currently in membership. :-)