Flex Duct - Does this product ever change

[martlet]

My 1976 flex duct in the attic is showing signs of age - it's brittle and in some places caved in. I've read some of the threads on this site with regard to the economy of replacement and from what others have said I have come to realize replacement may require a lengthly payback period.

We plan to stay in our house for twenty or more years. If we change the flex it should be now, not later. I am considering a long metal duct with flex running off of it but that will more than likely involve too much attic floor space to be useful and still leave enough room in the attic to walk around in.

Going back to the question of replacing the flex, I am wondering if there have been any advances in this product. With energy conservation so very important has anyone produced a "super flex" - even at a much higher price or do the laws of physics apply and limit the benefits beyond the current price/performance design of the product?

[beenthere]

Your 1976 flex duct is R4.2.

New flex comes in R6, and R8 insulation values.
And the exterior membrane is made better.

[MB1211]

I would also suggest insisting on the foil wrapped in the attic.

[martlet]

Beenthere - thanks - yes - I should have thought of this jump in R value and that will make a difference.

Ok - beyond that, are there any flex products that offer substantial improvements over other products? Are some exterior membranes better than others?

This stuff if used everywhere - just thinking someone must have tried to manufacture a much better product at a higher price. Is this possible?

[beenthere]

As everetts said, the foil wrapped.
Its a better radiant barrier for the duct.

[dash]

The flex with the gray colored outer jacket has not lasted well in hot attics.

The silver loking ,mylar( i think),jacket has lasted over 30 years in hot attics.

[kenny mac]

Condition Your Attic.... Then duct leakage is a benifit !!!!

Foam the roof, if you plan to stay in this home the 20 years!!!!

ESPECIALLY here in GA, increase efficiently, decreased moisture healthier home.

[adrianf]

I have no first hand knowledge regarding this product but we did have a sample; we just never did anything with it.

http://www.superiorairducts.com/

[adrianf]

Condition Your Attic.... Then duct leakage is a benifit !!!!

Foam the roof, if you plan to stay in this home the 20 years!!!!

ESPECIALLY here in GA, increase efficiently, decreased moisture healthier
home.

As more vendors come on line the foam insulation my become a more viable alternative. Retrofit by the correct company is mandatory.

[Shophound]

Condition Your Attic.... Then duct leakage is a benifit !!!!

Foam the roof, if you plan to stay in this home the 20 years!!!!

ESPECIALLY here in GA, increase efficiently, decreased moisture healthier home.

That looks great. The pricing policy of this forum may/may not allow us to discuss how much it cost to do an attic roof deck like shown in the picture. I'm personally curious as to the cost of the foam vs. radiant barrier roof deck, and the performance comparison. I do realize radiant barrier would require the attic remaining non-conditioned (i.e. ventilated) whereas the foamed roof deck, along with blocking off soffit, ridge, and other venting, could make the attic become conditioned space, thereby rendering duct leakage less problematic, and excess heat gain to or loss from the ducts virtually a non-issue.

[kenny mac]

That looks great. The pricing policy of this forum may/may not allow us to discuss how much it cost to do an attic roof deck like shown in the picture. I'm personally curious as to the cost of the foam vs. radiant barrier roof deck, and the performance comparison. I do realize radiant barrier would require the attic remaining non-conditioned (i.e. ventilated) whereas the foamed roof deck, along with blocking off soffit, ridge, and other venting, could make the attic become conditioned space, thereby rendering duct leakage less problematic, and excess heat gain to or loss from the ducts virtually a non-issue.

Go to my Profile and E-Mail me and I will be glad to answer ???? and help you locate you an installer.... You gain 30% efficiency when the ducts and air handler is in condition space..... Now you add duct leakage>>>>>

Don't think about cost, think about the investment,
If it were $5,000 to Foam a Roof at 6% 30 years would increase your mortgage about $29 a Month
Depending how many units or size of roof this would be a guaranteed wash but in reality it could double or triple that monthly investment.

[pstu]

Here is one product which claims to be an advance in flex duct quality and technology.
http://www.flexmasterusa.com/pg/fdpp.php

However I as a homeowner have not been able to find any HVAC pros using it, and it is not certain how much more it costs. For myself, would probably use modern silver R-6 or R-8 duct which I am told is far better than the old grey stuff they used to use.

Hope this helps -- Pstu

[Shophound]

Go to my Profile and E-Mail me and I will be glad to answer ???? and help you locate you an installer.... You gain 30% efficiency when the ducts and air handler is in condition space..... Now you add duct leakage>>>>>

Don't think about cost, think about the investment,
If it were $5,000 to Foam a Roof at 6% 30 years would increase your mortgage about $29 a Month
Depending how many units or size of roof this would be a guaranteed wash but in reality it could double or triple that monthly investment.

Well, I don't have a mortgage and I do have radiant barrier, so the questions regarding foamed roof deck were more from general interest on my part...I do have a friend interested in this process, as he has an attic similar to the one in your earlier attached picture. I am also always interested in the various ways to improve thermal efficiency of a residential structure, as I may at some future point look into energy rating and HVAC consulting as a sideline operation. I am particularly interested in hard data, not sales hype, as the only way I can get enthusiastic about a product, strategy, or process is to actually measure (or read of measured) performance. Benefits only come from performance...if the latter is not there, neither will be the former.

[njhusky]

Kenny Mac,

Does foaming the roof really do any good if you have gable vents?? especially since I have an exhaust fan in the vent. How much of a temp drop would you expect in the attic by adding the foam?

[dash]

Go to my Profile and E-Mail me and I will be glad to answer ???? and help you locate you an installer.... You gain 30% efficiency when the ducts and air handler is in condition space..... Now you add duct leakage>>>>>

Don't think about cost, think about the investment,
If it were $5,000 to Foam a Roof at 6% 30 years would increase your mortgage about $29 a Month
Depending how many units or size of roof this would be a guaranteed wash but in reality it could double or triple that monthly investment.

So 30% ,won't the A/C now be 30% or more oversized??

Plus duct gain and duct leakage?So 45% oversized.

[kenny mac]

Well, I don't have a mortgage and I do have radiant barrier, so the questions regarding foamed roof deck were more from general interest on my part...I do have a friend interested in this process, as he has an attic similar to the one in your earlier attached picture. I am also always interested in the various ways to improve thermal efficiency of a residential structure, as I may at some future point look into energy rating and HVAC consulting as a sideline operation. I am particularly interested in hard data, not sales hype, as the only way I can get enthusiastic about a product, strategy, or process is to actually measure (or read of measured) performance. Benefits only come from performance...if the latter is not there, neither will be the former.

Hard Data !!!!
Well that was my "Roof Picture" taken 2 years ago.
It is sitting over 12,200 sqft conditioned space Total Electric.
5 Tons of Heat Pumps (1 2ton and 2 1.5 Ton) Trane XL gear...
Average Electric Bill $180.00 per month next two months high $200.00's
And I have dozens of homes similar stats...

Get Ya Some Of That..........

[hvaclover]

Here is one product which claims to be an advance in flex duct quality and technology.
http://www.flexmasterusa.com/pg/fdpp.php

However I as a homeowner have not been able to find any HVAC pros using it, and it is not certain how much more it costs. For myself, would probably use modern silver R-6 or R-8 duct which I am told is far better than the old grey stuff they used to use.

Hope this helps -- Pstu

PTSU got it right on the money. There are flex duct products that have a higher R value then the foil covered R8.

One member here showed some pics. The insulation was thicker than (looked that at least) then the duct diameter. Looked hard to use too.

[kenny mac]

Kenny Mac,

Does foaming the roof really do any good if you have gable vents?? especially since I have an exhaust fan in the vent. How much of a temp drop would you expect in the attic by adding the foam?

Seal them all OFF... Condition the Attic like a Closet!!!!

[kenny mac]

So 30% ,won't the A/C now be 30% or more oversized??

Plus duct gain and duct leakage?So 45% oversized.

Dash Your Good!!!!

Dash, now we have to deal with Thermal Drive, Moisture Drive, Solar Drive, Humidity Reduction and Added Volume. (Good Problem)
Because we eliminated Stack Pressure, Convection, Negative Pressure, Latent Load, 70*DT, Stored Energy. (Bad Problems)

For it to be "Oversized" it would have had to been sized right in the beginning.

Don't get me wrong... I am very passionate about Manual J's and it should be done. But unless you can do a Thermal Bypass, your for the most part in the dark.
A REMRATE Comparison could be done, which a Blower Door Test for leakage after the Foamed Roof would have to be done, to see if the HVAC needs reduce.

Thanks,

[BigJon3475]

Most systems are oversized to start with.