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Old 07-20-2018, 02:01 PM   #16
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Re: Cathedral Ceiling Redo


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Originally Posted by arcticranger View Post
Just FYI that same author Martin Holladay warns against cut and cobble for vented OR unvented ceilings and cites various disasters. He then provides instructions for doing both. In the same article!


http://www.greenbuildingadvisor.com/...ble-insulation
So have another look at venting.
What kind of roofing do you have and what does the roof look like behind the chimney.
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Old 07-20-2018, 02:31 PM   #17
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Re: Cathedral Ceiling Redo


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Originally Posted by ryansdiydad View Post
Did you discover any issues or signs of issues when you opened up the ceiling?

At some point someone, maybe Bud, provided a calculation for the amount of venting required for an addition on my house. You maybe have enough to leave it vented? Have you looked in to a calculation for your place?

The baffles are just spacers used to keep insulation away from the decking..

My cathedral ceiling has a badly leaking skylight. It did cause damage to the ceiling and a bit of the sheathing which will get repaired this week. So I've stripped it and am considering my options.


Not sure what you mean by a calculation. My rafters are 11" so there's plenty of room, but spacing alone is not ventilation, is it?
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Old 07-20-2018, 03:00 PM   #18
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Re: Cathedral Ceiling Redo


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Originally Posted by Bud9051 View Post
But I definitely prefer vented assemblies.

Bud

I frankly don't trust myself or anyone around here to make it airtight. So maybe the best thing is to figure venting out first and then go with the assembly @ryansdiydad described.



Here's a pic. The only soffit vents are on either side of the chimney outside. The dark space over the brick is just where I've not finished retiling the fireplace. And I haven't pulled out all the foil insulation yet.



Any ideas on getting airflow into those middle bays?



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Old 07-20-2018, 03:05 PM   #19
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Re: Cathedral Ceiling Redo


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Originally Posted by Nealtw View Post
So have another look at venting.
What kind of roofing do you have and what does the roof look like behind the chimney.

It's the Owens architectural stuff, Duration. I'll have to go look and see how the tile meets the chimney. My ladder was just stolen so...lol
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Old 07-20-2018, 03:10 PM   #20
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Re: Cathedral Ceiling Redo


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It's the Owens architectural stuff, Duration. I'll have to go look and see how the tile meets the chimney. My ladder was just stolen so...lol
Can you get much the same picture from the out side where the chimney reaches the roof.
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Old 07-20-2018, 03:17 PM   #21
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Re: Cathedral Ceiling Redo


If you mean from ON the roof looking at the chimney I need to get a new ladder.
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Old 07-20-2018, 03:18 PM   #22
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Re: Cathedral Ceiling Redo


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If you mean from ON the roof looking at the chimney I need to get a new ladder.
No from the ground for now.
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Old 07-20-2018, 03:38 PM   #23
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Re: Cathedral Ceiling Redo


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Old 07-20-2018, 03:42 PM   #24
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Re: Cathedral Ceiling Redo


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Originally Posted by Nealtw View Post
No from the ground for now.

I'm not seeing my own images let me know if you can. I could replace the left and right soffit vents with long continuous vents but the rafters behind the fireplace still wouldn't be vented.
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Old 07-20-2018, 04:09 PM   #25
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Re: Cathedral Ceiling Redo


No pictures as yet.
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Old 07-20-2018, 04:10 PM   #26
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Re: Cathedral Ceiling Redo


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Originally Posted by arcticranger View Post
I'm not seeing my own images let me know if you can. I could replace the left and right soffit vents with long continuous vents but the rafters behind the fireplace still wouldn't be vented.
Behind the chimney there should be cricket or saddle that looks like this.

A box vent or ridge vent might be able to be placed on that and then you would just cut into the cavity from below.
The other question is why did they put solid blocking above the window.
I doubt it was needed other than holding things in place during construction and a few 2" holes thru them would not hurt anything.


There are also vents much like the ridge vent that can go lower on the roof but that is disturbing the roof likely more than you would like.
I will down load that picture and post it.
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Old 07-20-2018, 04:12 PM   #27
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Re: Cathedral Ceiling Redo


the insert from URL is not working so here are direct links

http://randomorbit.com/rafters.jpg

http://randomorbit.com/chimney.jpg
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Old 07-20-2018, 04:13 PM   #28
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Re: Cathedral Ceiling Redo


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Old 07-20-2018, 04:27 PM   #29
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Re: Cathedral Ceiling Redo


https://www.owenscorning.com/roofing...ent-calculator

I canít see the pictures but the calculator should help you figure out how much venting you need at the soffits and ridge...

Seeing the pictures might make this irrelevant so someone correct my mistake if this just doesnít apply in this case
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Old 07-20-2018, 04:28 PM   #30
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Re: Cathedral Ceiling Redo


Those look like substantial rafters (perhaps larger than necessary) so one might consider many holes along the top edge to allow bay to bay air movement. This approach is common with a hip roof where rafter bays don't go all the way to the top. Not the best and should have local code approval, but it could get some air in there from each side. Also depends upon good venting in those side bays.

Lacking ventilation can be minimized by better air sealing and a good vapor barrier across the bottoms of those rafters.

Bud
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