Ducts...What's Best

[lksmith]

I've been soliciting bids from HVAC dealers to put a dual-fuel system in a new house I'm building. I've had four different companies give me three different options on duct work. I'm clueless on whether one option is better than the other.

1) Fiberglass ducts.

2) Metal with internal insulation.

3) Metal with external "wrapped" insulation.

If it makes a difference, the ductwork will be in a crawlspace.

Is this an issue in selecting a HVAC company?

Thanks. LKSmith

[Jack2007]

As a homeowner I've had a problem with Fiberglass ducts.


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[DGIO-Not]

As a homeowner I've had a problem with Fiberglass ducts.


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Perhaps the better questions is lifespan of systems and what will it take to replace them.

Ductboard and internally lined insulation according to 2007 study (by the way, lumped together by home study...not what an HVAC contractor actually sees) has a life span of approx. 20 years. In my area, duct board does not even make this mark. Internally lined we see approx. 20 years. So basically, when comes time to replace system, it is time to replace duct work too.

Choose to ignore "way down the road, might not even own home?" Now look at what you are putting into your airstream. These are things that are fiberglass in nature, treated with chemical to prevent breakdown. So what is your Indoor Air Quality?

By the way, many of us are working with the real estate profession to educate them on the difference and code is changing very quickly on us. Do you really want to chance your resale value on a few $$$?

Metal duct, sealed properly..mastic person here, then externally lined will last as long as the house if no catastrphoic happening occurs. Worse comes to worse, we are usually replacing external insulation only.

Not only that, Manual D tells us it is usually the better fit for your construction as far as air flow (static pressure v size required) and usually fits very nicely in construction measurements...making it much more a bargain at the end of the day.

[Jack2007]

Metal duct, sealed properly..mastic person here, then externally lined will last as long as the house if no catastrphoic happening occurs. Worse comes to worse, we are usually replacing external insulation only.

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I had my fiberglass ducts replaced with metal but the tech, an acquaintance, used "long life" clear caulk (I forget the proper name) to seal seams.

Is that as good as the mastic ???

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[DGIO-Not]

I had my fiberglass ducts replaced with metal but the tech, an acquaintance, used "long life" clear caulk (I forget the proper name) to seal seams.

Is that as good as the mastic ???

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You are Quick!

You are going to hate this answer as it is no answer at all. "Long Life" Clear caulk is not an industry strandard nor tested in studies that I have been exposed to. Quite frankly, I would want to see tube's Material Safety Data Sheet before I advised regardless as it falls outside tested realm (well studies I have been exposed too.)

Mastic is so simple but so perfect in its function. I would have not even thought of using something else in it's stead. Sorry.

Good News, if the two of you decide this was not the right application, mastic will forgive you alot (not tape of course...tape will almost certainly fail and pull mastic away with it.) You do have me curious though, I would like to test that statement if you could provide me with product name and specs. Doesn't answer your question, but could be beneficial for others in future.

[lksmith]

DGIO-Not

Thanks for your input. Sounds like externally wrapped metal is the way to go. Happy 4th.

LKSmith

[lolson]

DGIO-Not

Thanks for your input. Sounds like externally wrapped metal is the way to go. Happy 4th.

LKSmith

My personal opinion is that you made a good choice

[quickcat46]

Yall already made the decision before I got to the stories about mold and mildew in the ductboard and Internal lined metal Duct. Well just for the record any moisture that becomes trapped in either of these two types is at risk of becoming a serious health hazard. In many cities the code will prevent one from installing these types of ducts. The insurance industry got beat up pretty good on mold and mildew claims a few years back.

[Mark T]

Metal ductwork has no “friable” particulate matter + is easier to clean (internally) + structurally sound + not subject to “seam” failure + the list goes on . . . .

[steve3871m]

#3,metal. Lowest friction rate. Ask for sound attenuation procedures if going all metal,

[suzook]

#3,metal. Lowest friction rate. Ask for sound attenuation procedures if going all metal,

What options are there for this?

[beachtech]

properly installed flexible duct is the best IMO

so quiet you won't even know the system is running

easy to clean to if you choose to pay a guy to clean it years from now

and is very resistant to duct sweat it will sweat, but is pretty good at not sweating

[heaterman]

Metal ducts with outside wrap.