# Need advice on vaulted ceiling insulation



## jaminduncan (May 12, 2010)

I have a vaulted ceiling above our front room in our 1967 ranch house in Huntington Beach, CA

I'm in the process of replacing all the insulation in the attic. This vaulted portion is problematic because there is only about 6" of space in each chute between the 2x6's. Each chute is about 20' long and 6" high. Currently there is a very thin strip of roll batt that's only an inch or so thick. Some of the chutes don't have anything!

I can look down each of the chutes from that attic and see all the way down to the round soffits which are at the end of each chute, probably 20 or so in all.

A couple insulators have told me they cannot do anything for me to fill the space, one told me they would shoot cellulose down there as best they could.

The room faces the rising sun in the morning so the room gets very hot. Should I just fill the spaces as best I can with blown in and block the soffits with the cellulose in an effort to provide some insulation from the sun, or should I leave it alone and leave them open so air can flow through the chutes?

By blocking the airflow am I going to build up moisture in there leading to wood rot?

The attic itself seems to have plenty of ventilation other than those soffits, there's gable vents and two rotating circle vents out the roof. The other side of the house only has soffits every 2 or 3 chutes instead of along every single one like the vaulted area.

Help!


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## tpolk (Nov 7, 2009)

take the dry wall down, sister deeper framing to vault framing, use proper insulation and soffit venting with insulation baffles


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## seeyou (Dec 12, 2008)

Rent a blower and fill it full of Cellulose. Pack it as tight as possible.


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## jaminduncan (May 12, 2010)

So it's okay to block the soffits? It won't create moisture in that area?


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## tpolk (Nov 7, 2009)

you sure will


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## seeyou (Dec 12, 2008)

jaminduncan said:


> So it's okay to block the soffits? It won't create moisture in that area?


You won't have a moisture problem if you don't have moisture. If you dense pack cellulose, you won't have any air movement to carry any moisture into the area.

http://energytrust.org/trade-ally/weatherization/attic-insulation-requirements/#at2_7


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## Scuba_Dave (Jan 16, 2009)

Do NOT block the soffits
Air movement is required


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## jaminduncan (May 12, 2010)

So even though there's plenty of ventilation in the rest of the attic, I shouldn't block air flow from the vaulted ceiling room?

Better to have the sun warm the room and little to no insulation than no airflow?


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## seeyou (Dec 12, 2008)

Let me back up. In my locale, dense packing a vaulted ceiling will work. In more northern climates, there could be an issue with moisture, but there are ways of addressing them short of leaving your vault as leaky as it is. Give us some location info before a vent war gets started.


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## Scuba_Dave (Jan 16, 2009)

If you are in CA you are using AC ?

So.....cool AC air hits warmer air...moisture
Or you have heat on at some point...cooler air hits warm air...same thing
I've never seen any method that blocks 100% of moisture/temp transfer

And being in a hot climate you will shorten the roof life without ventialtion
Many Mfgs you void the shingle warranty without ventialtion
Proper ventilation AND enough insulation will get rid of both problems

Rafter vents are installed, then insulation
Get R22 insulation if possible
Best bet is to fir out the studs for more insulation


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## seeyou (Dec 12, 2008)

cooler air hits warm air...same thing
I've never seen any method that blocks 100% of moisture/temp transfer

Yeah, but if there's no space for air to move in the vault then then there's no air moving through it and consequently no moisture transfer - or very little. 

And being in a hot climate you will shorten the roof life without ventialtion
Many Mfgs you void the shingle warranty without ventialtion

That used to be true about the warranties, but not any more because it was based on misconception. Yes, the sheathing surface may be a few degrees warmer, but not enough to make any significant difference in shingle life. Every shingle manufacturer I'm familiar with changed that clause years ago. 

Proper ventilation AND enough insulation will get rid of both problems. 

That's true, but without major re-construction, those two items together are not an option. Cellulose and closed cell foam don't have the condensation problems that fiberglass batts do.


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## jaminduncan (May 12, 2010)

We're in So. California. We do not currently have AC, it's fairly temperate being about a mile from the beach, however there are a couple weeks in the summer we wish we had AC. We definitely use heat in the winter.

We're replacing the old 1" 1967 insulation with new R-30 in the attic to see if it will help keep things cool before we invest in AC. That front room could negate any benefit though if the sun continues to heat up that room.

SeeYou-you said "there's ways of addressing them short of leaving your vault as leaky as it is"

I'm guessing the only real solution is to rip the drywall down and lower the vault to accommodate air flow AND insulation, but short of that, you have any ideas?

Sound like so far the consensus is, between packing it with cellulose as best I can or leaving as is with little to no insulation but keeping airflow, the latter is the better.


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## jaminduncan (May 12, 2010)

seeyou said:


> That's true, but without major re-construction, those two items together are not an option. Cellulose and closed cell foam don't have the condensation problems that fiberglass batts do.


So you think trying to pack in the cellulose with a machine is the best way to go without doing major re-configuring?


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## Scuba_Dave (Jan 16, 2009)

You want to blow in 5.5" of insulation & think that will solve everything ?
Its your house, do what you want
R30 is what they recommend as a Min


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## seeyou (Dec 12, 2008)

jaminduncan said:


> So you think trying to pack in the cellulose with a machine is the best way to go without doing major re-configuring?


Yeah. 

From what I understand, the whole house is not vaulted and the rest of the attic area is vented. Is there a source of humidity (kitchen or bath) underneath the vaulted area? Is there a vapor barrier under the existing vault insulation? 

If no vapor barrier exists, I'd at very least paint the vault ceiling with a vapor barrier paint and if there's a source of high humidity, I'd make sure those areas are well served by exhaust fans and use them religiously when boiling water or bathing. 

My humble opinion is that 5 1/2" of dense pack cells trumps no insulation, but you have to keep the humidity somewhat controlled. 

Major re-configuring would be the best solution - either adding extra insulation/venting space from the bottom or raising the roof when the time comes to replace it. But I don't think you'll get yourself in too much trouble if you dense pack the cellulose.


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## jaminduncan (May 12, 2010)

Thanks for the advice. Even if I do pack it with cellulose, I don't know if I'm getting enough R-value to really cut down the heat at the expense of airflow. There's no source of humidity below the vaulted room, just the front living room.

I guess someday I'll have to pay someone to rip down the drywall and add a deeper vaulted area to accomodate R-30 and airflow. Any idea how much that would run me for a 20'x12' room.


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## seeyou (Dec 12, 2008)

Scuba_Dave said:


> You want to blow in 5.5" of insulation & think that will solve everything ?
> Its your house, do what you want
> R30 is what they recommend as a Min


So your recommendation is don't do anything? I don't think anyone has suggested that 5 1/2" of cellulose will "solve everything". It's only a partial solution. But the ROA will likely be much higher than your proposal of "Holmes on Homes" guerrilla tactics.


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## Scuba_Dave (Jan 16, 2009)

If its worth doing, its worth doing right


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## tpolk (Nov 7, 2009)

Scuba_Dave said:


> If its worth doing, its worth doing right


uhoh i got to fix some stuff


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## seeyou (Dec 12, 2008)

Scuba_Dave said:


> If its worth doing, its worth doing right


OK - I'll buy into that. But there's more than one way to skin a cat and "Holmes on Homes" guerrilla tactics aren't always the only solution.

He's got maybe R5 or R6 there now with convection problems. Dense pack cellulose nets about R3.5 per inch. 5.5 x 3.5 = about R19 with less convection. R values are victims of diminishing returns. The 1st R19 gives a better ROA than the 2nd R19. 

I agree the best solution is to add more insulation depth and vent against the sheathing. But, he can increase his comfort level and pocket some savings in the interim to pay for that major project. And he could insulate upwards when it's time to re-roof.

Cheers.


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## jaminduncan (May 12, 2010)

seeyou said:


> vent against the sheathing


What does that mean?


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## Scuba_Dave (Jan 16, 2009)

tpolk said:


> uhoh i got to fix some stuff


some...dontcha mean a lot :laughing:
I've saved the cost of new windows in the entire house on lower heating costs over the past 5 years

Paying for the correct way ONCE is much cheaper then paying to have it done twice
R30 is my min insulation on pre-existing 2x10 rafters
Everything else is R38 min with some areas R49 or higher
Orig 2nd floor ceiling insulation was R7
I ripped the ceiling down & put in R30 & R38


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## tpolk (Nov 7, 2009)

seeyou said:


> OK - I'll buy into that. But there's more than one way to skin a cat and "Holmes on Homes" guerrilla tactics aren't always the only solution.
> 
> He's got maybe R5 or R6 there now with convection problems. Dense pack cellulose nets about R3.5 per inch. 5.5 x 3.5 = about R19 with less convection. R values are victims of diminishing returns. The 1st R19 gives a better ROA than the 2nd R19.
> 
> ...


 i agree with that if its a financial wait. i also worry about nail pops after packing if not filled correctly


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## seeyou (Dec 12, 2008)

http://www.diversifoam.com/certivent.htm


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## seeyou (Dec 12, 2008)

tpolk said:


> i agree with that if its a financial wait. i also worry about nail pops after packing if not filled correctly


From my experience, if a 1967 drywall ceiling hasn't nail popped yet, it won't show any pops with a Lowes cellulose blower. I'd be more concerned about getting a dense enough pack.


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## seeyou (Dec 12, 2008)

Paying for the correct way ONCE is much cheaper then paying to have it done twice

That's not necessarily so and certainly not true in this case. If he's DIYing this, he probably won't spend $400 to go from R-nothing to R19. Give me a cost estimate on your proposal and lets compare ROA.


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## jaminduncan (May 12, 2010)

One estimator quoted me $207 to fill the vaulted area as best they could with cellulose. That was in addition to the rest of the attic which they quoted me $1145 for faced R-30 batt installation and $700 to clean out the old insulation.


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## seeyou (Dec 12, 2008)

jaminduncan said:


> One estimator quoted me $207 to fill the vaulted area as best they could with cellulose. That was in addition to the rest of the attic which they quoted me $1145 for faced R-30 batt installation and $700 to clean out the old insulation.


Is the R30 in flat ceiling area? I'd leave the old insulation and blow cells over it in that area as well in most scenarios.


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## jaminduncan (May 12, 2010)

It is flat. I was going to do blown in but I'm going to be doing a lot of installation of lights, fans, etc, so with the blown in I wouldn't be able to see the joists to walk on cause they're only 6" high, so I decided to go with batts.


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## seeyou (Dec 12, 2008)

jaminduncan said:


> It is flat. I was going to do blown in but I'm going to be doing a lot of installation of lights, fans, etc, so with the blown in I wouldn't be able to see the joists to walk on cause they're only 6" high, so I decided to go with batts.


Put some walkway boards down where you need them before you blow or better yet, put your lights and fans in first. Be sure to use IC rated units.


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## AaronB (Jan 29, 2005)

seeyou said:


> Rent a blower and fill it full of Cellulose. Pack it as tight as possible.


This is bad insulating advice. You need cellulose and fiberglass insulation to be loosely packed in order to trap the air needed to provide insulating properties.

Find a foam insulator that does pour in place. He can get this done.


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## AaronB (Jan 29, 2005)

tpolk said:


> take the dry wall down, sister deeper framing to vault framing, use proper insulation and soffit venting with insulation baffles


I think it would be cheaper and easier to remove the roof and foam it from the outside unless youre talking about doubling the depth of the framing, you can get double the insulating factor with foam with the same space.


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## AaronB (Jan 29, 2005)

jaminduncan said:


> So it's okay to block the soffits? It won't create moisture in that area?


This is another reason to go with Closed Cell foam... it is a vapor barrier and will not allow moisture in out or through.

No insulation creates moisture.


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## AaronB (Jan 29, 2005)

Scuba_Dave said:


> Do NOT block the soffits
> Air movement is required


This is partially true, but also mostly not.


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## AaronB (Jan 29, 2005)

Scuba_Dave said:


> If you are in CA you are using AC ?
> 
> So.....cool AC air hits warmer air...moisture
> Or you have heat on at some point...cooler air hits warm air...same thing
> ...


Moisture would have to be present in the inside to condense on interior surfaces. In your example, air conditioned air carries MUCH less moisture than warm air. Moist air will deposit moisture on COLD surfaces, but the moisture must be present in the air, which it wouldn't be if the air is on.

Now, heated air will carry moisture when then heat is going. this means that it would most likely be cold outside. If you're properly insulated, your dew point should fall somewhere within the insulation assembly, not at either surface. This means that the hot/cold interface would not be exposed to each other, and condensation could not occur.

Also in your example, R 22 is ok for moderate climates for purposes of heating, but depending on where you're at, you would want a bit more than that if you're heating OR cooling your indoor climate. 5" of CC foam will yield the theoretical numerical number of R-33, depending on the blowing agent.


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## AaronB (Jan 29, 2005)

Also, it has been shown that you do not necessarily shorten roof life without ventilation, if you dont have higher than ambient attic temps. This is why foaming to the bottom of the deck makes so much sense... it does not allow interior heat at the roof, nor outside heat to the living space.

Foam is not a heat sink substrate. Neither is wood roof decking.


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## AaronB (Jan 29, 2005)

seeyou said:


> cooler air hits warm air...same thing
> I've never seen any method that blocks 100% of moisture/temp transfer
> 
> Yeah, but if there's no space for air to move in the vault then then there's no air moving through it and consequently no moisture transfer - or very little.
> ...


Nice post, copper


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## seeyou (Dec 12, 2008)

AaronB said:


> This is bad insulating advice. You need cellulose and fiberglass insulation to be loosely packed in order to trap the air needed to provide insulating properties.
> 
> Find a foam insulator that does pour in place. He can get this done.


That may be true for blown fiberglass. Google "dense pack cellulose" and/or "Mooney wall". I know guys that have been dense packing cellulose for many years with great results. Not as good as closed cell foam, but a better ROA in many cases, the OP's scenario looking like a good fit to me.


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## AaronB (Jan 29, 2005)

seeyou said:


> That may be true for blown fiberglass. Google "dense pack cellulose" and/or "Mooney wall". I know guys that have been dense packing cellulose for many years with great results. Not as good as closed cell foam, but a better ROA in many cases, the OP's scenario looking like a good fit to me.


I will check it out... I am always better off with up to date information.


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