Flex Duct - Does this product ever change

[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.

[nites chaos]

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.

Shop,
At one time in the not so distant past I did several searches on this very topic. On a average I found most prices running from .99 - 1.25 per board foot installed . This was for a 1" layer that they say gives a value of R7.

We have two install companies here in town that have added a complete truck setup to their fleet and are offering this service. They also sub out their "foam truck crew" to other companies. Some HO's are hiring them just for the foam service they offer. The truck stays busy from everything I've seen and appears to be paying for itself...

Martin

[kenny mac]

Shop,
At one time in the not so distant past I did several searches on this very topic. On a average I found most prices running from .99 - 1.25 per board foot installed . This was for a 1" layer that they say gives a value of R7.

We have two install companies here in town that have added a complete truck setup to their fleet and are offering this service. They also sub out their "foam truck crew" to other companies. Some HO's are hiring them just for the foam service they offer. The truck stays busy from everything I've seen and appears to be paying for itself...

Martin

Are you saying some company is renting their foam rigs to someone who has never foamed ????
If so... who pays for a cross over and fill the lines ($6k) or the pump ($20K) or both full of foam.... thats CRAZY!!!

And are you saying they will rent the rig and sub their guys ????
HUM !!!! Thats no different than what I do except the HO knows exactly the cost before the start and I have all the GL, WC, ins. and I have my manufactures backing.

Where are they going to buy the foam ??? My manufactures want sale to the public !!!!!!

[BigJon3475]

Are you saying some company is renting their foam rigs to someone who has never foamed ????
If so... who pays for a cross over and fill the lines ($6k) or the pump ($20K) or both full of foam.... thats CRAZY!!!

And are you saying they will rent the rig and sub their guys ????
HUM !!!! Thats no different than what I do except the HO knows exactly the cost before the start and I have all the GL, WC, ins. and I have my manufactures backing.

Where are they going to buy the foam ??? My manufactures want sale to the public !!!!!!

To much coffee?

[DanW13]

We have a outfit here that does foam insulation and is busy 6 days a week. I do not believe they sub out to others but I do know they are very busy with the spray foam. I can see the company sub there equipment to other contractors but the contractor uses the guys from the insulators company to run there rig and not just rent and let other contractors run a foam truck without any experience !!

[oldheathen]

I suspect their internal ridges in flex lowers the efficency of moving air, whan compared to rigid (sheet metal) ducts. Am I right to assume that the flex slows down airflow compared to the rigid?
By how much?

Also, I suspect the flex would a better job if it laid flat and straight, as opposed to doing the serpentine thing over ceiling joists, let alone by them being wrapped arounf roof truss supports. Is this correct, and, if so, to what extent?

Thaks again folks!


















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[beenthere]

7" metal does move more air then 7" flex at the same FR.
Which is only a problem when people try to use a ductulator for sheet metal on flex duct.

Yes poor installation methods can hurt the air flow in flex. The same as it can with sheet metal duct.

Har pipe doesn't flow a lot of air when installers kink it.