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jaminduncan 05-12-2010 03:02 PM

Need advice on vaulted ceiling insulation
 
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!

tpolk 05-12-2010 04:07 PM

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

seeyou 05-12-2010 04:19 PM

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

jaminduncan 05-12-2010 04:20 PM

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

tpolk 05-12-2010 04:25 PM

you sure will

seeyou 05-12-2010 04:41 PM

Quote:

Originally Posted by jaminduncan (Post 441023)
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/we...rements/#at2_7

Scuba_Dave 05-12-2010 05:02 PM

Do NOT block the soffits
Air movement is required

jaminduncan 05-12-2010 05:12 PM

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?

seeyou 05-12-2010 05:12 PM

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.

Scuba_Dave 05-12-2010 05:17 PM

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


http://www.crossworksme.com/images/A...013%20copy.jpg

seeyou 05-12-2010 05:27 PM

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.

jaminduncan 05-12-2010 05:29 PM

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.

jaminduncan 05-12-2010 05:32 PM

Quote:

Originally Posted by seeyou (Post 441080)
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?

Scuba_Dave 05-12-2010 05:41 PM

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

seeyou 05-12-2010 05:49 PM

Quote:

Originally Posted by jaminduncan (Post 441082)
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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