High velocity flex ducts

Andy Michl

I have see a number of you talk of Unico & Space Pak systems. The question I have is how long does the duct work last. One of my competitors is telling consumers that fiberglass duct board falls apart after 5 years. This seems unrealistic to me. If anything the duct system fit togather much tighter than metal duct with insulation wrapped around the out side of the ductwork. What have you seen in the feild after 5 years with high velocity systems?

Mark J Strawcutter

flex duct is not fiberglass

The flex duct part is aluminum - rather like some of the newer dryer vent but smaller. It's wrapped with foil-backed fiberglass much like conventional duct-wrap I've used.

The plenum for Spacepak is 11in OD 9in ID round 1in compressed fiberglass like ductboard. It's also coated on the inside. I believe it's Johns Manville "super round" duct.

Unico also has provision for using metal plenum - which you'd need to insulate of course - if that would be a selling point to some customers.

Mark

Mark Hunt

I haven't seen


a high velocity system with duct board. I use Hi-V by E.S.P and they recommend round spiral duct for the supply trunk.

These units work with higher pressure than a typical air system and I don't believe that duct board is a recommended material for installation for that reason.

That being said, I have seen quite a few standard air systems with duct board and in nearly every instance the board has begun to come apart. In one case a duct cleaning company sent a crew to a home that had duct board and they ran a brush down the supply and return mains. Somebody should have known better, but ALL of the duct had to be replaced. The brush tore up the fibreglass which blew throughout the house.

I worked for a VERY large HVAC company for 17 years and even they wanted nothing to do with duct board. The owner said that it would be a liability someday.(?)

For high velocity systems it's spiral duct, ALL joints sealed with mastic, and 3" of foil faced duct insulation wrap.

I can't guarantee what duct board would do, me thinks it would blow apart, but I can guarantee that spiral duct will be here until they tear the house down!!

Hope this helps!

Mark H



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Andy Michl

I have installed one unico to date. The reason for asking about the durability is that a large home I am bidding has little or no space for duct work. My competitor is claiming only a 5 year life span for either duct board or flexible supply tubing. I have seen the plain flex fail but it was much longer than 5 years and it was not properly installed or protected. I was planning on rigid pipe for the main duct sealed with mastic and insulated.

Mark Hunt

OH!!!

So what is your competitor going to use for the run-outs? I can only imagine that he thinks he's found something cheaper??

The system you have proposed is exactly what the manufacturer has recommended, I bet your competitor can't say that.

I have never had flex duct go bad.

You stand your ground, as I know you will. You're design is founded on truth, and NOTHING can stand agianst that!!!!!

Mark H

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Mark J Strawcutter

apples and oranges

Part of the problem is that your competitor is comparing conventional flex duct with that used by unico/spacepak. They are two totally different products.

Mark J Strawcutter

still does

Current Spacepak still uses ductboard.

It's just that now it's curved instead of flat :-)

Andy Michl

Thanks for the vote of confidence. I just had to check if any of it was justified. And make sure my butt was covered.