R8.0 Duct Insulation and Flex Duct

[chrisc]

I'm located in NJ and more and more I'm hearing about inspectors knocking down jobs because of substandard duct insulation and flex duct. I understand that all permits pulled as of Jan. 1,2008 requires R8.0 insulation, that's a pricey proposition for customers especially in this economic time of uncertainty. Anyone running into this situation.

[beenthere]

Been R8 around here for over a year.
But only in unconditioned uninsulated areas.

Adds a bite to the price. But so did 13 SEER.

[Nubicon]

Yeah, I've known about it for a while and have been harping about it at my supply houses. They still only carry R4...but I can order R6:rolleyes:

Then again I still see my competition passing inspection with no insulation at all. I don't know if the code enforcement helped or hurt:confused:

[Carnak]

A sealed attic with the icynene and 50 CFM supply air is conditioned space

[Nubicon]

A sealed attic with the icynene and 50 CFM supply air is conditioned space

That's interesting. Around here if you seal an attic and don't install the proper vents (soffit, ridge, sidewall) the house will fail inspection. But I get your concept...only I wonder how the HO would feel about spending fuel money to heat an attic so the HVAC guy didn't have to insulate the duct?

[jrbenny]

50 CFM ain't squat.

How much do you think the HO spends to heat the ducts in the unconditioned attic?

$$$$$

[Nubicon]

50 CFM ain't squat.

How much do you think the HO spends to heat the ducts in the unconditioned attic?

$$$$$

That was kind of the point. The HO should not have to at all...but I see it every day. And due to the fact that you can't "seal" an attic here you won't be heating it with 50cfm either.

An inspecter made me put a 12x6 supply grill on the ductwork (insulated R6) in a crawlspace with seven crawlspace vent windows around the perimeter. Sometimes you just gotta do it and move on.....

[jrbenny]

You need to introduce the code inspector to a code book. Sealed attics are not a code violation.

[smadave]

Im from NJ also and like you said there is alot of talk about guys getting knocked down for using R-6...hasnt happened to me yet knock on wood. Of course the people telling me this happen to work at the supply house I buy from but...anyway the R-8 is another 5 bucks a box and thats adds up real quick you know!! I know it wont be long before I make the switch...I also hear metal is going up again...I guess I better start printing my letter of price increase!

Dave in NJ

[Nubicon]

Im from NJ also and like you said there is alot of talk about guys getting knocked down for using R-6...hasnt happened to me yet knock on wood. Of course the people telling me this happen to work at the supply house I buy from but...anyway the R-8 is another 5 bucks a box and thats adds up real quick you know!! I know it wont be long before I make the switch...I also hear metal is going up again...I guess I better start printing my letter of price increase!

Dave in NJ

Hey, Dave. I'm from just over the border in PA. It's actually the opposite here as far as the warehouses go. They are still selling r-4 and you have to fight to get them to order r-6. If you mention R-8 they blink at you and try to change the subject:o

I'm getting mad because I have to compete with guys still using
r-4...and they get away with it.

[weber]

R8 is better so why fight it.

If it is required in your area, use it the first time.

Just remember to bid the job accordingly.

[mark beiser]

That's interesting. Around here if you seal an attic and don't install the proper vents (soffit, ridge, sidewall) the house will fail inspection. But I get your concept...only I wonder how the HO would feel about spending fuel money to heat an attic so the HVAC guy didn't have to insulate the duct?

You are not understanding the concept.
The insulation is at the roof line, the attic is part of the conditioned space, no insulation between it and the rest of the house.
When it is done properly, the HO would be spending 10-30% less to heat the home, even though there is more "conditioned space".

[Nubicon]

Yeah, I have that concept down pat.

Nobody here was talking about a finished attic (is that what some of you mean by "sealed"?). We were talking about metal trunk lines in unfinished attics with no insulation/wrap. Most of the time the heating unit is stuffed into the attic as well. R-38 insulation between living space and attic floor. No insulation in the rafters.

And further, are you trying to imply that finishing an attic and heating/cooling it could represent a 10-30% reduction in cost to the HO?

[jimj]

And further, are you trying to imply that finishing an attic and heating/cooling it could represent a 10-30% reduction in cost to the HO?[/QUOTE]

;) In initial cost no, in operating cost yes.
The thermal barrier is at the roof line not at the ceiling line.
no heat loss/gain for the ducting.

[jrbenny]

That's interesting. Around here if you seal an attic and don't install the proper vents (soffit, ridge, sidewall) the house will fail inspection. But I get your concept...only I wonder how the HO would feel about spending fuel money to heat an attic so the HVAC guy didn't have to insulate the duct?

You posted this in response to Carnak's icynene response. Thus, the conversation turned to a sealed attic and the fact that's cheaper in the long run for the consumer.

If your inspection department would fail a sealed attic, then ask them what they think about cathedral ceilings. ;)

[Carnak]

That's interesting. Around here if you seal an attic and don't install the proper vents (soffit, ridge, sidewall) the house will fail inspection. But I get your concept...only I wonder how the HO would feel about spending fuel money to heat an attic so the HVAC guy didn't have to insulate the duct?

You do not vent a sealed attic.

You add a minimal amount of air and it is conditioned space, therefore the new stringent rules of increased insualtion do not apply.

I am not saying do not insulate. I am saying you do not have to go the extra yard for the R-8.

Uninsulated ducts in a conditioned space are fine until something goes wrong. So like I said, if you seal an attic, cutting edge technology in some climates, and add minimal supply air to it, it is a conditioned space and the rules for unconditioned spaces do not apply.

[Carnak]

COnsider a sealed attic over a 1000 sqaure foot home, 50 CFM of supply air

Attic will be possibly 80F in the summer.

Now consider you do not seal it. Have as much insulation as you want blown in. Underside of roof deck is 160F, radiating down at all your blown in insulation, attic air heated to 130 F, would be even higher except for the vents. Vents by the way, which are there so that you do not get icylces and ice dams on your roof in winter.


So now which attic do you think is the bigger energy penalty, one you can keep at 80F with a minimal amount of supply air, or one which is in essence a superheated sauna, that allows hot humid air to infitrate in around pot lights?

[nites chaos]

R8 flex, 3" Duct Wrap and 2" Duct Liner here in Georgia is required on any permit pulled after 1-1-2008 in "unconditioned space". Because so many of the supply houses in my area sell to both GA and Al contractors, several are still stocking both R6 and R8 as well as both 2 & 3 wrap and 3 thickness's of liner.

Some counties in Alabama still allow use of 2" wrap and R6 Flex, some have adopted Ga Code, supposedly Alabama state code will change Jan 2009 and become unified as Georgia is.

Martin

[Nubicon]

You posted this in response to Carnak's icynene response. Thus, the conversation turned to a sealed attic and the fact that's cheaper in the long run for the consumer.

If your inspection department would fail a sealed attic, then ask them what they think about cathedral ceilings. ;)

They would call it a cathedral ceiling, as it in no longer an attic? And when you do have a cathedral here you are required to install styrovent in the bays near the soffit and then insulate the roofline with
R-38.

And I can think of a hundred reasons why a HO would want to leave their attic unfinished. I'd like to see it worked out on paper how adding square footage is more efficient? All you succeed in doing with sealing the attic space is changing where the roof heat load is. From between the rooms below and the attic floor to the finished attic ceiling and the roof itself.

[jrbenny]

Maybe carnak will share some of his numbers. He's done it on his own place..

[Carnak]

I have a sealed attic, roof insulated with a total of about R7.

I compared numbers with jrbenny, I would say it works as well as R30 under a vented attic. That was before I added any supply air up there. It averaged about 81F and 50% RH as an unconditioned space.

Heat transfer then is what 81F can drive through a a sheet rock ceiling to air beliow the ceiling, heat rises so keeping my place at 78F would mean about 79F at the ceiling. 81-79 equals 2F driving heat transfer through sheet rock and two air films.

My wife is storing some heirlooms in the attic, so I added about 40 CFM of supply air to guarantee a low humidity. With the minimal supply air, my attic averages about about 79F and humidity ion the 40s.

So now the air in the attic above the ceiling is the same as the air below the ceiling and there is no heat transfer. A small amount of humidity wicks through the ceiling plane as the space below is a little dryer

An extremely wealthy woman here, remodelled the top floor of an office building she owns here and made it into her penthouse town apartment, it exceeds 8000 square feet.

Because of what happened here in a hurricane, wind driven mositure entering in through soffit vents saturating and ruining ceilings before a roof even failed, she wanted no vents.

I was hired by her attorney to advise what to do. So you have to be pretty careful when dealing with wealthy people and their lawyers. I ran the numbers and by sealing the attic and blowing R19 icynene under the pitch of her dark sloping roof, it would take about 4 tons to keep that attic at 80F, which was roughly eaqual to what the heat gain would have been through R19 layed flat above the ceiling plane.

But what you also need to consider is that numerous fan coils and insulated duct work in the attic are not being radiated by hight temperature heat and losing 10% of their cooling capacity. So in this case, less heat gain by conditioning the attic.

My weasel clause advise on sealing up the attic to this attorney, "Add dehumidifiers as sensible heat gain will be reduced", especially since all the AC was already installed, designed around heat coming through the ceiling.

Another thing to consider is in many climates it is extremely difficult to have an attic vapour barrier on the warm side of the insulation. Vapour barriers also stop infiltration. All it takes is a slight pressure differential and attic heat and humidity will pass right through fibre glass insulation just like return air through a filter.

So in some climates, the sealed attic eliminates all the heat and humidity bypassing the insulation.

Go through Building Science sometimes, they will call a sealed attic with 25 CFM a conditioned space. Big difference between conditioned and finished.

[Carnak]

The sealed attic is in the face of anyone who does light commercial work. It is the same thing as the ceiling space in a shopping mall with a flat roof.