Unico Flexible ductwork longevity

clutterbug

Any idea of the lifespan of Unico’s high velocity flexible ductwork? We have a 10 year old system and the tubing disintegrated in the entire house. Some tubing is in insulated attic, some in conditioned basement. All that’s left is metal coils and the surrounding insulation. Is this normal? Anyone else have this experience?

mikeg2015

I haven’t heard anything specific. But I wouldn’t expect it to last any less that normal flex. Maybe 30-40 years. But it does use a fabric type material in some of it to reduce noise level. Not sure what that’s made out of . I could see that if the insulation is not adequate and the outer wrap is not well sealed, you could get a lot of condensation inside of it.

Personally, I very underwhelmed with my system. It was installed before I started working in residential HVAC myself.

I find mine to be Noisy, inefficient, leaky, TXV failed right away box (probably install issue). On top of that it’s expensive. Would have been a LOT, LOT better to just install a large mini split system and have zoning in each room. With combination of ducted units, cassettes and wall mounts.

Ther units would be kinda OK, installed with R8 tubing, explicitly as shown with a full perimeter loop trunk, and chilled water or a mini split type coil.

UNICO support is poor too. They go through your dealer only and only sell mainly through Lennox dealers now it appears. SO if your dealer is incompetent, your screwed.

Couple notes other notes

1) Only use metal ductwork and mastic, mastic, mastic.
2) Insulate to R8
3) Don’t use with heat pumps
4) Design for 250CFM/ton
6) Use 10 2” outlets per ton if you want it quiet.


Long term, I might replace the main trunk so it’s sealed and insulated properly and can run at and ESP under 0.9. Add more outlets and install a standard 2ton cooling only AHU running at 700CFM. Rather than I estimate 2.2 Tons at 600cfm (3 ton unit on low stage, too many air leaks and noise on high stage).

mikeg2015

Can you post pictures of some of the ductwork internal, external and how it’s installed???

clutterbug

Sure, but pardon my markups. We are under construction so the ceiling and grills are removed. All The runs and the trunk lines are insulated and all are in insulated and humidity free space. Some of the runs and trunk lines are in the traditional fiberglass insulation some are in blue jeans insulation and some are in foam insulated areas.
Unfortunately we are not in a position to replace this entire system so we’re going to have to replace the runs only.
Thank you for your really long and informative email.

SuperTech

I have seen the Unico ducts disintegrate like that in a few houses. I'm not a fan of those systems, I think they are low quality.

Last one I saw was in an old Victorian home, they ripped out all of the cast iron radiatiors and the Steam boiler and installed a hydronic boiler and two Unico air handlers with hydro coils. They used the holes in the floor that the risers went through to run the Unico ducts to. Kinda clever but the whole job looked awful and it made my stomach turn seeing a historic home like that hacked up.

clutterbug

Thank you SuperTech. I feel helpless and want to warn others who may read this and be contemplating a Unico install.
My installer tried to show the tubing to Unico who 1) refused to physically examine it and 2) said it was my fault due to exposure to something, likely moisture.
??? Okay then. It’s helpful for me to know if I replace the runs will I have the same experience in 10 years? And helpful to know if others experienced the same issue, which you say is yes. Well warning to all...stay away from Unico.
Ours is heat and a/c and heat is sourced via our outdoor wood stove and a water to air heat exchanger in the air handler.

Sad about that old Victorian. If I could have cast iron radiators... 😀.

Jon_blaney

Was the insulation on the supply tubes sealed to the outlets.
Where is you air return located? It looks to me like you have a lot of moisture it the system.

I have a UNICO system I designed and installed mostly myself. I had a plumber hook up the hot water coil and an A/C guy do the A/C work. I bought the parts at the local supply house with no problem. If you read the literature it is mostly plug and play. Any problems I have had over the 15 years it has been running can be attributed to operator error not the equipment.

I think you got a bad install.

SuperTech

Lol. I got the cast iron radiatiors, they were all left in the basement. I'm in the process of converting some of them from one pipe steam to hydronic. They will be going in my finished basement.

Tinman

In my opinion Unico and SpacePak are not created equal and I’ve installed/serviced plenty of both. Unico is a spin off from SpacePak by a specific company that installed many of them going back to the Dunham Bush days.

I’ve compared every component of each and I think SpacePak’s quality is much better.

clutterbug

Does spacepak tubing work with a Unico system? We are between a rock and a hard place. Can’t afford to change out the air handler, but have to replace all the ductwork. It would kill me if it did the same thing in 10 years
The system itself has worked flawlessly for these past 10 years except that on a hot day it has to run all day to move the house one degree. Ditto when we have zero degree days. I’ve bypassed that issue by leaving the fan on constant on when it’s 95 and humid out. Fortunately here it’s only about 2 weeks a year.

Jon_blaney. Ummm air handler is in conditioned basement. Returns on first and second floors. To the best of my knowledge the insulation was sealed to the outlets. I base this on what I can see.

Unicos response to looking at a photo was that the tubing was that it had been exposed to moisture. Well...our house is dry if anything.
And where it is crumbling the worst it was in an attic crawl space...ceiling joists insulated...ridge and soffit vents.

Thoughts? And thank you in advance.

mikeg2015

I’m guessing the sheathing wasn’t sealed and humidity migrated in there and condensed on in inner liner.

Unico is very sensitive to installation. You have to tape their fiberboard seams with special tape and a special procedure.

clutterbug

I did have a reputable installer put this system in who has since installed over 100 of these systems, just in case anyone’s thinks it was a DIY 😀

Tinman

Yes, you can use SpacePak tubing on Unico systems. I’d use their takeoffs and termination kits as well.

clutterbug

Thanks Steve..this gives me some hope. Do you know what material their tubes are made of? I am also not a fan of noise...is Spacepak as quiet as Unico?

Tinman

As long as you’re at 7 full outlets per ton, don’t exceed 1.5” w.c. on the supply and .25” on the return, it will be quiet. If you exceed those static pressures, you don’t have enough supplies or your return is starved.

stlvortac

We looked at buying a Victorian with a unico system installed in the attic. It was 13 years old at the time and I looked it over throughly. I didn’t see any sign of deterioration in the ventilation system. Thinking back I guess the system was a bit loud but the air handler/return was installed over the back hallway. The down side was it had about 6 vents per ton on a 4 ton system, 2500sf house.

While the ductwork was done correctly they really hacked up the floor in the attic and had horrible vent placement, not in corners, some in the middle of the room directly over beds.

Fortunately it was an AC only system and the radiators were still in place as the sole heating system for the house.

mikeg2015

Steve Minnich said:

As long as you’re at 7 full outlets per ton, don’t exceed 1.5” w.c. on the supply and .25” on the return, it will be quiet. If you exceed those static pressures, you don’t have enough supplies or your return is starved.

Steve Minnich said:

As long as you’re at 7 full outlets per ton, don’t exceed 1.5” w.c. on the supply and .25” on the return, it will be quiet. If you exceed those static pressures, you don’t have enough supplies or your return is starved.

I have 27 outlets on 3 tons and it’s still noisy by my standards above 600CFM. My 2 ton conventional is silent in comparison at 800CFM with just 5 registers.

Tinman

@mikeg2015
Which brand?
Did the contractor use 3’ sound attenuators at the end of each supply?
What are the lengths of the supply branch ducts?
What are the static pressure readings?
Did the contractor use OEM specific return duct and filter box/grill?
These things matter as does placement of the supplies.
Manufacturer instructions must be followed precisely on these systems.

clammy

I have seen the same happen to foil flex due to hi moisture or the flex had gotten wet and starts to disintegrate after being exposed to hi temp .i have also seen it look like that when exposed to hi temp from hydro air and flex installed in unconditioned crawl spaces using the r 4 flex . I just install unico system for over 25 years and I usually see jobs that are done by hacks wheather it’s unico hi bee or space pack .the bad jobs are usually all the same no long main trunk 26 gauge 5 ft rd pipe regular elbows no tapped joints and all the take off right where they say not to . Most of all unico I have installed is 8 per ton and a perimeter loop of spiral duct all sealed each run gets a full attuntor . I will say when we bid against other contractors on them there always cheaper and we lose a lot ,but some we come back and re do cause the ho realizes they where hosed and cannot get the original contractor to fix . The truth is if u don’t follow or read the duct design and installion instruction and follow there’s going to be issues and if your company is the type that has you hand into every business but master of none w what I call non tradesman as employers then most likely ur gonna get a crap job .as I always say I’m not here to change the world just to change my little corner of it . Peace and good luck clammy

mikeg2015

Steve Minnich said:

@mikeg2015

Which brand?

Did the contractor use 3’ sound attenuators at the end of each supply?

What are the lengths of the supply branch ducts?

What are the static pressure readings?

Did the contractor use OEM specific return duct and filter box/grill?

These things matter as does placement of the supplies.

Manufacturer instructions must be followed precisely on these systems.

UNICO.

Yes, we used the fabric core sound attenuator. He had to come back and replace or extend most supples to the recommended minimum length to most of the runs. They are 3’ minimum, most are 4-6’. a few are 8-10’.

Static pressure I believe was around 1.2”. But t’s been a while. He supposedly fill out all that info for UNICO when I first complained and took CFM readings.

NO, he made his own cobbled return box and it connects to a filter grills. I think it’s 14”x20”, plus another 8” supply to the master bedroom/bath with a 10”x20” filter. I think it’s the UNICO square to round transition at least. He used 10’ of 16” flex. I’ve thought about adding a 16x25 Air Bear after the return box and ditching the filters. Should help the return.

Main trunk makes a T and goes approx. 45’ one way and 55’ the other way I estimate. He made his own “T”

Also, supplies are bunched together near the end of one main (against installation recommendations. First take off is only 3’ from the initial T.

I’ll bring my tool bag home tomorrow and take some new readings with the manometer at different air flows.


Have a 2 stage 3 ton heat pump (might disable it and leave it in cooling permanently) and it requires 250CFM/ton or it trips out on high pressure. Even after adding a pressure switch to turn off the outdoor fan. I can’t even imagine how inefficient t is heating. I need to check the delta T and put my amp meter on it some time.

In cooling, it runs fine down to even 200FM/ton. FOr now I’ve disabled 2nd stage and run it at 563CFM. (75% of 3 tons). Its OK at that speed but would be silent at 500CFM like my downstairs system.

In hindsight, I would have just installed a conventional 2 ton cooling only AC, but both contractors were insistent I needed 3 tons and. I didn’t want that much supply and ductwork cut in all the ceilings and running all over the attic. 2 tons could have fit within the knee wall space easily. 4 x 8” plus 3 6” for the bathrooms and a smaller center 4th bedroom bedroom, then just cut transfer grills into the center hallway.

Tinman

@mikeg2015 I believe the minimum branch duct length is 9'. The spacing between branch ducts is 12". I understand your frustration but I believe if the installer did the job the way it was suppose to be done, you'd probably have a different take.

Voyager

I don’t know what brand of flexible duct and fiberboard was used in my system, but after 19 years it still looks like new. The only issues I have had is a few seams in the main fiberboard ducts had to be taped again after the tape adhesive dried and started to come loose.

My flex ducts have black plastic on the outside that looks and feels like heavy garbage bag material and has held up well.

I was nervous at first about the fiberboard/flex duct material in lieu of metal, but the designer at the contractor (a local commercial outfit) assured me that this was a good solution if properly installed. So far he has been right, but my house is only 19 years old so too soon to really tell as to longevity. No doubt metal will last longer if kept dry, but it sure is harder to install, seal and insulate.

clutterbug

Thank you Voyager and everyone else for your comments, help, knowledge, sharing your experiences. I am grateful. Once we remove all the supply tubes and try to make sense of what happened. I will post an update. Thanks to all.

Ironman

I'm a dealer for both Unico and SpacePak and we've never had the issues you're experiencing with either one.

The one thing that both manufactures preach about during their training classes is getting every bit of the duct and tubing COMPLETELY sealed from ANY air leaking. Otherwise, condensation will form from the leakage.

The moisture damage (condensation) is from cold air leakage from the ducts. It's not a matter of how "dry" your house is.

I'm not knocking your installer, but most high velocity systems that I've seen done by other contractors were NOT done correctly, no matter how many they have done.

clutterbug

Okay. Point taken thank you I have a question for you. Up in the area where we’re having the most problems is an attic crawlspace under the roof with ridge and soffit vents. As it turns out and we don’t know the reason yet, some of the runs came detached From the main trunk line. I have as yet to crawl up there and have a lock I’m not sure what they used to attach the Runs to the Trunkline Possibly something corroded. My question being in Theory if those runs came detached could that cause this problem. Sorry for the typos I dictated this.

Ironman

Anywhere there's air leakage could cause it to happen.

The more I'm hearing, the more I doubt the quality of your installation.

Lance

you could even try 2" duct made for whole house vacuum systems and insulate with armor flex. No problem use 3" . Just calculate air velocity, cfm, measure and build, and verify build with testing. Most don't size properly, use enough openings per ton because it is cheaper to buy. Internal ducts may not need insulation but try and stay out of attics and crawls. good advice for all duct pipe. Be advised this system is based on a different humidity base. It can tend to make the air dryer. 35-40% RH. It is at this level many are comfortable at 78F. But some may find it too dry if they are sensitive to dryness. all depends on the application. Possibility for failure: Failed to keep moisture out of ducts in winter and frost occurred in ducts. They make 2" plugs for outlets. And the returns should be blanked off also for cooling only applications.

clutterbug

Ironman...I hear you. And Lance...it’s heating and cooling so not sure it could be a frost thing. I do understand how the system makes the air less humid. The air handler is in my basement and this particular trunk line is in the attic as described. Trunklines are in 3 places...basement and two different insulated attic crawl space areas. The runs in the basement have also disintegrated. I have yet to check the runs from the other attic area. It’s like going to the dentist for me : afraid of what I am going to find.😳😳
Update. Installer coming tomorrow. Will post what we find

clutterbug

Okay so. Runs in both parts of the attic I.e., the part with fiberglass Insulation and the part with foam insulation had the same amount of deterioration see the photos. The one that interest me the most is the one that shows how the insulation itself turned black. (1st photo) and then most of them, all that’s left is wire.

SuperTech

Yup, that's exactly what I have seen. For what it's worth the installation was really low quality, octopus style flex runs coming off of a duct board box for a plenum. Plenty of air leakage.

clammy

Where all your flex runs deteriorated like that ? Or was it the one which where dis connected if so the reason for the issue would be condensation forming inside the flex most likely caused by a chimney effect drafting from the attics unconditioned space w it’s soffit and ridge vent to the living area causing condensation to form due to the temp difference .i would hope that a black mold did not form maybe that’s why unico wouldn’t t look at .or on another note this is also used for heat? If it could just be from chimney effect and not putting those winter shut off caps ? Peace and good luck clammy

clutterbug

It’s both heating and cooling Clammy. Used all,year round. Supertech, I will double check but fairly certain The plenums are formed metal ductwork with these runs going off to it. Just like the Unico installation shows. It looks like an octopus now because we pulled it all off and stuffed it in a box. Thanks for your help+ thoughts

clammy

Where all the flex’s effected ? Just wondering what kind of filter was on the system ,could that just be accumulated dirt and dust from a ineffective filtration system .i always install Aprilair media filters on all residental ac equipment and 2 inch pleated on commercial equipment . Not a fan of the box type Honeywell media filter I ve just seen to many freeze up s when used in lieu of OEM Aprilaire filters .i know unico uses a freeze stat mounted on the suction line to protect the coil from freezing ,I have seen cases where the coil would freeze up shut down the condenser till the coil defrosted and the freeze stat resets .in which case unless your there it melts resets and no one knows it usually goes by mostly unnoticed until it its peak season and its 90 in the house . I think aside from the black junk I would chk air flow ,duct size and length of runs number of runs and then head out to the condenser and chk your refregerant charge sub cooling and superheat then chk ur td across your coil to manafactures specs. Also go over ur condensate lines and make sure there clear pitched and your pan is draining . On a small note the unit in the attic is the attic well ventilated or is it about 1 million degrees in the summer . That hi temp could be enabling condensation to form inside the flex just aidea wish u the best of luck in find out what the real issue is . Peace and good luck clammy

clammy

Is your roof spray foamed if so u have indoor air quality issues usually caused by not enough air exchange I think that may be playing into your issues . Where u located . I’m in New Jersey and listed on the site as R A Calmbacher LLC Peace and good luck clammy

mikeg2015

Ummm no, a little fine dust from a MERV 7 filter instead of a 8 or 11 will not cause the duct to fail like that. If it did, the design is junk. a 5” pleated vs a 1” only difference is pressure drop. Airflow is already low on a Unico but they do prefer minimal vacuum on front of blower.

Just foaming the roof won’t seal up a older home, as I assume this is. It just seals the attic. That’s very significant, but You still have windows, doors and the sill plate. I had a foamed roof in a previous home. It certainly was not air tight. Still ran a humidifier most of the winter.

However, high humidity in winter would be a contributing factor. But again, I think the design is poor. I hear that most HV systems in 10-15 year get ripped out when the coils leak and fail and they are prohibitively expensive or obsolete by that time.

I wish I had researched more. In hindsight, I would have done 3 slim duct mini splits for the whole house one 5 ton condenser and been done. Probably have cost about 30% less than what I spent, 30% more efficient and had 2 upstairs zones.

GW

Back in the day it was 5 outlets per ton, 1 1/2” tube. I had one in my house. The noise didn’t bother me but it sure was loud. When we renovated it went away.

SuperTech

I haven't seen a high velocity new installation in years now. I think the slim duct units have made the space pack and Unico systems nearly obsolete.

clammy

I still install hv when no one wants to see multi lines sets and multi outdoor units and don’t want to much of a mess especially in older homes . I think the real issues are they are not being installed correctly in just about every aspects. From not enough outlets to non sealed duct work to crappy duct board .some we just yank everything out re do supply ducts hang the unit re do refregerant line basically re do the whole job and when we get done it’s quiet and works . I think a lot has to do w not getting the correct money for the job and un skilled un supervised un familiar installers doing the work .i given many quotes on unico s over the years and I think maybe 1 outta 5 go for it the rest just lug window units every season from the basement or garage to the window or they get a unrealistic price and go for it.i get some that just can’t afford the re do so I tell them call when it’s dead and the next one will be right .most that I do see always have the lowest builder special outdoor units a real pos it s sad when u spend all that coin and get a 10 or 11 seer outdoor unit just stupid .i always try to give the equipment the benefit of doubt and install it correctly at least giving it a chance to work properly and follow the design and installation procedures manuals provided from the manafactures and have really had no issues none more then a standard systems .as for noise I can’t say I hear standard systems that sound worse then a hv because of the same issues bad install, and let’s no forget the miricale insulation bubble wrap cause the installer don’t like fiberglass extremely humorous to myself .i hate insulation but I despise bubble wrap and believe it’s useless and a underperformer .i still do stuff the old way except w r 8.5 instead of the r 4 wrap loosely staple re enforced taped and wire ties ,of course all joints either masticed or hardcast taped is there any other way not for me at least as for sub work I do I use a line from mad max what ever you want lol peace and good luck clammy

SuperTech

Almost every high velocity system I see is very poorly done, usually just a box for a plenum and the return is flex run to a collar that's screwed on the unit with a piece of metal or duct board. Rotting drain pans from badly pitched units with no drain traps. Air leakage everywhere. I know they can be good when done correctly but I rarely see it. And the outdoor unit is always a builder grade York or Goodman.

clammy

So it isn’t just me that see all the good stuff ,I sometimes feel that I’m too judgemental of the shabby work and feel worse when asked what can we do to improve the comfort of the space . I can usually only reply is to do it over ,very sad but I think in most cases there getting what they paid for also .The difference is expense is only the difference between being comfortable and be uncomfortable .peace and good luck clammy

mikeg2015

If your really lucky, you pay nearly full price and it’s still a poor performer. Actually pushed me into the industry. Now one out of 5 jobs if following this same companies junk installed from 10-15 years ago to redo them. Installing a heat pump tomorrow that was a ductwork nightmare.