more insulation for attic ductwork?

rileysmom17June 2, 2008

My HVAC ducts in the attic sit on top of the insulation. They are 1 year old, flexible type. I had an energy audit and the auditor said I did not need deeper insulation. He was 'impressed' with the new system which he said had been well-installed. However I do notice warm (in summer) or cold (in winter) air blowing out of the vents when the system initially turns on, so clearly there is heat loss/gain across the system. Is there something I can lay over the ductwork, like the equivalent of a hot water heater blanket, to help this?

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I wouldn't cover the ducts for ease of location in the future. The air temperatures upon start-up are pretty normal; it takes a few moments to get up to temperature. Adding more insulation in the attic will likely only make things better in terms of energy efficiency (not just for the ducts), but it may not be necessary and may not improve your situation. Do you have any solid metal ducts that the flexible ducts connect to? You could insulation those (trunk lines). Hope this helps--maybe someone else will have a different opinion.

    Bookmark   June 2, 2008 at 6:05PM
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You can't put two vapor barriers on ductwork, as condensation will form between them.

ducts should be strapped off attic floor & insulation.
in strapping the ducts there should be no more than a
1" sag in ducts per 4' run.

your money would be better spent in mastic sealing the ducts ( did your energy auditer test for duct leakage..
or was it just a freebie thru utility co?) Home & duct work should have been tested if you hired an independent

please post more info so we can better address your issues.
Best of luck.,

    Bookmark   June 3, 2008 at 10:13PM
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I paid for the audit, and the auditor was groping the air handler and the ductwork...I was like, "what are you doing" and he said "feeling for leaks". All of the joins have some type of rough tape around them and then they are smeared over with a brown-gray goo, I would guess this is mastic. I originally had a duct system with large ducts splitting into smaller ones, I had it converted so that each ceiling opening had its very own duct, with baffles, so that I could balance the air flow how I wanted it. Thus there are no seams in the actual ducts.

I have never heard of suspending the ducts up in the air, how does that help?

    Bookmark   June 4, 2008 at 7:39AM
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strapping ductwork provides a better air flow and with peoper duct layout & sealing will improve the comfort of your home. Also ducts in contact with other ducts, or insulation will cause condensation. Never a good thing.
wetting insulation on attic floor can cause a lot of problems.
and it is code, code being the legal minimum allowed.

I test & feel for leaks but also measure the amount of ductleakage. not uncommon to find 1 1/2 to 2 tons of leakage. When I measure the leakage, I then take home owner into attic so that they can 'feel' leakage..
( also measure/show return air leakage.)
and offer proper sealing methods with instructions as to]
how to seal based on my experience.

brown stuff over tape...I recommend/use a paint on mastic on new construction, and usually a foil mastic tape on existing homes...sometimes a combination..depends on the
It may be before my time...the brown stuff over tape.

what part of the world are you in?
I'm hot humid La.

    Bookmark   June 4, 2008 at 10:10PM
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I am not an expert in attic ducting but... I know enough to say that suspending the Ductwork is not the route you want to take, the only way to efficiently insulate attic ducts is by using the Ultimate-R, along with sealing the joints with mastic, this application uses blown cellulose allowing you to get an R-38 which brings the ducting into the thermal envelope, creating conditioned space for your attic ductwork.

Here is a link that might be useful: Ultimate-R

    Bookmark   July 23, 2008 at 1:55PM
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ultimate r..
explain please. your site does not show what product you are selling is, does or what it is comprised of.
clarify your post as it is somewhat confusing.

btw suspending ductwork is code in my state.

    Bookmark   July 23, 2008 at 2:46PM
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Quick websearch turned this up-

"Ultimate R is an insulation containment system which is installed over supply and return air ducts in attics. It is simple and fast to install and facilitates the installation of substantial amounts of blown insulation around the ducts. The result is reduced conductive and convective losses from the ducting in summer and winter, both when the air handler is working and when it is not."

Heres an old study with install pics:

Guess we know why he doesnt like suspended ducts, can't get the containment boxes around it. Of course since 1998, flex duct and it's R values have come along way.

    Bookmark   July 23, 2008 at 10:43PM
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I'm not sure I agree that duct work has come a long way in the past several years. What I do know is that many homes have the duct work sitting on the attic floor with a very small amount of insulation wrapped around them. Ultimate-R can certainly help but prior to installing the containment system you want to be sure and properly check for any leakage. The prep work that takes place prior to installing Ultimate-R can really make a difference. Regarding the suspended ductwork, we blow them separately and usually after we install Ultimate-R and blow the duct work on the ceiling floor. Whichever comes first always depends on the attic layout. Our customers swear by the product and I know personally that it makes a tremendous difference in the air quality of the home and esecially in the upper levels of 2 story homes where it is difficult to keep cool. Also, we've learned a lot from many other insulation installers who install Ultimate-R as they've shared ideas on the application itself. It will make a major difference in the air quality, comfort level and utility bills but Ultimate-R really only addresses one of many areas that need to be addressed when making a home more energy efficient and improving the comfort level in the home.

Any other ideas please share them.

    Bookmark   July 24, 2008 at 2:59PM
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I keeping hearing about air quality improvement with this Ultimate R yet, donÂt see any filtration or other measurable means of improving the quality of the air

The Air Quality Index (AQI) is a standardized indicator of the air quality in a given location. It measures mainly ground-level ozone and particulates (except the pollen count), but may also include sulfur dioxide, and nitrogen dioxide.

The term "air quality" and its improvement is a false and misleading term in everyoneÂs advertisement with regards to Ultimate-R.

You are merely insulating better than existing that is there. Perhaps improved air temps should be referenced, but not air quality.

There was a time when R4 flex was the standard. Now we have R6, R8, R10, class 1 insulation, puncture resistant vapor barriers and more. And you say flex duct hasnÂt improved?

    Bookmark   July 24, 2008 at 5:20PM
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I think that flex has improved.
Just in the years I have been in the trades I have seen
failed grey duct due to degradation & breakdown from uv light..and just a little uv light. duct dries & splits.
silver flex duct with grommets to attach strapping to that split open bewteen grommets. black ducts holds is that good? (maybe for heating climates??)

and best of all upgrade of the legal minimum of ductwork from R 4.2 to R 6 and R 8.

Installs and sealing of ductwork can always improve.

It seems to me that a LOT of time is spent with the
layout of the product in question.
I also don't see that externally insulating the duct with
celluose enclosed in box would have any effect on IAQ.
although it is a good 'claim'.
it is the sealing of the ductwork that is important.
Use of mastics for ductsealing is the only way to go.
I've tested too many systems to believe different.
old mastic - new mastic..that stuff stays sealed when
properly installed.

and zl700..thanks for the link I'll go look at it but between you & me..I don't put much faith in studies performed on products that are paid for or studied by the mfg of the product. Call me a skeptic, I am! Just have learned to get my information from unbiased sources.

sorry to get off topic OP.

    Bookmark   July 25, 2008 at 12:52AM
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Actually Synertech Systems Corporation
Syracuse, NY was involved and I am familiar with them.
(former central NY resident and now vacationer)

However, procedure is old and many options have become available and perhaps more cost efficient to perform since 1998

    Bookmark   July 25, 2008 at 10:17AM
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Ok, you guys are correct. There is probably no improvement in indoor air quality. I didn't mean to mislead. What I meant is that the air comfort level is improved. And regarding the improvement in duct work...Ok it has improved some. I'm not old enough to be familiar with old duct work. I'm only able to judge off of what's in the home's we're entering into now and most were built before 1980. Just blew some insulation into the attic of a large home last weekend and per our request for an update from the homeowners we got feed back such as..."It is literally cold upstairs since you guys installed Ultimate-R." And we haven't even blown the entire attic, just into the UR containment system. rileysmom17, you should try Ultimate-R. I'll send you some for free if you want to contact me directly. If you're going to have a local insulation company blow new insulation in your home just let me know who they are and I'll get the product in their hands along with instructions. Thanks for the feedback everyone...I'm sure everyone here would like to help each other improve the quality of life and be more efficient about our use of energy.

    Bookmark   July 25, 2008 at 6:33PM
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I'd like to see the info.
you can email me thru my member page, if you would.
I have not seen your product locally.

and you are right..we all learn. thanks for sharing your
experience. glad to see you so excited about your work.
its a great feeling to do something you love isn't it?

I visit a hvac site with hall of shame & hall of pride installs. you can get an idea of bad ductwork and different situations you may encounter there. let me
know if you want to take a look.

    Bookmark   July 25, 2008 at 10:51PM
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Thanks guys for your info and thoughts. Because of my attic shape and the duct layout the Ultimate R system would be a whopping hassle to install. Looking at the quoted study it seems the payback period could be very long as well. I already have low utility bills thanks to my Schuco windows and my new 13 (or was it 14) SEER systems. The attic ductwork is all brand new as well. So I'll pass on this product. Sounds like it might be a good option for others. Best option in new construction is just to put the ductwork inside the 'offical' conditioned space.

    Bookmark   July 30, 2008 at 2:49PM
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Glad you were able to look in your attic and see the layout. And you're right, the duct work should be in a conditioned space but if it's not it makes sense to insulate it as best you can. Good luck to you and if you change you're mind and want to see what a difference it can make just let me know.

Also, I don't have a lot of time to check up on my posts especially after a long hot day in attics but I will try to do a better job. Energy Rater LA, thanks for understanding and sharing some info. Always good to hear from people who've been around the block and seen the old and the new. I'll keep an eye out for your posts as I've learned some good stuff. Thanks to everyone else as well for sharing.

    Bookmark   July 31, 2008 at 12:10PM
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