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Discussion Starter · #1 ·
I built a 30' x 50' shop with exposed rafter tails with NO possible access thru the soffit area for ventilation. I have started to have moisture problems on the ceiling and in the attic so I am installing Core-A-Vents product called In Vent on the roof about 30" up from the dripedge. This is really a hassle and it was stupid on my part not to provide ventilation to the attic or rafter bays when I first built it. Let me tell you more about its construction. The rafters are 2 X 8's and it is a tray ceiling with ceiling joists starting about 6' in from the outside wall. I used 6" insulation so there is a 2" air space on the top side of the insulation. It is also a hip roof. I am installing the In Vent on all 4 sides of the roof. My question is whether to use ridge vent or a power vent as the means of expelling the moist air out off the building. The ridge is only about 20' long because it is a hip roof.
 

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Eater of sins.
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I built a 30' x 50' shop with exposed rafter tails with NO possible access thru the soffit area for ventilation. I have started to have moisture problems on the ceiling and in the attic so I am installing Core-A-Vents product called In Vent on the roof about 30" up from the dripedge. This is really a hassle and it was stupid on my part not to provide ventilation to the attic or rafter bays when I first built it. Let me tell you more about its construction. The rafters are 2 X 8's and it is a tray ceiling with ceiling joists starting about 6' in from the outside wall. I used 6" insulation so there is a 2" air space on the top side of the insulation. It is also a hip roof. I am installing the In Vent on all 4 sides of the roof. My question is whether to use ridge vent or a power vent as the means of expelling the moist air out off the building. The ridge is only about 20' long because it is a hip roof.


Jesus man, I don't mean to be an ******* but it just turns out that way sometimes.

What the F do you mean the ceiling starts 6' from the wall? Give us the pitch of the roof, sketch a cross section of the RRs and the CJs where they land.
Refer to the CJs as the rafter ties and tell us how HIGH they are from the top plate of the walls.
What kind of insulation are you talking about?

God Damn man.


Andy.


P.S. Sorry, frustrating day today.
 

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If you heat your shop and are in a cold climate, 6" is no where near enough...and if it fiberglass it's worthless in a cathedral application. I think your problem is an improperly designed roof system. Ventilation will not solve your issue if you continue to use fiberglass.
 

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Discussion Starter · #5 ·
Jesus man, I don't mean to be an ******* but it just turns out that way sometimes.

What the F do you mean the ceiling starts 6' from the wall? Give us the pitch of the roof, sketch a cross section of the RRs and the CJs were they.
Refer to the CJs as the collar ties and tell us how HIGH they are from the top plate of the walls.
What kind of insulation are you talking about?

God Damn man.


Andy.



P.S. Sorry, frustrating day today.
I do not how to draw it and post but I could post photos if someone could tell me how to do that.
If you have ever heard of a tray ceiling you would not have to ask these stupid questions. The ceiling is sloped as it is attached to the underside of the rafters about 6' from the wall, then the level ceiling starts. The type of insulation and roof pitch are irrelevant to the problem or the solution, but it is cotton insulation and a 6/12 pitch.
 

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Waltwood said:
I do not how to draw it and post but I could post photos if someone could tell me how to do that.
If you have ever heard of a tray ceiling you would not have to ask these stupid questions. The ceiling is sloped as it is attached to the underside of the rafters about 6' from the wall, then the level ceiling starts. The type of insulation and roof pitch are irrelevant to the problem or the solution, but it is cotton insulation and a 6/12 pitch.
Calling Andy stupid won't get you any help...they are relevant questions...and the type of insulation is most certainly a relevant question!!! You have the wrong type of insulation for your application!
 

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Discussion Starter · #7 ·
If you heat your shop and are in a cold climate, 6" is no where near enough...and if it fiberglass it's worthless in a cathedral application. I think your problem is an improperly designed roof system. Ventilation will not solve your issue if you continue to use fiberglass.
I heat my shop about 6 months of the year and I am located in south VA. The shop holds in heat very good with this amount of insulation. I know what the code is and this is not a house so it does not have to comply.
 

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Waltwood said:
I heat my shop about 6 months of the year and I am located in south VA. The shop holds in heat very good with this amount of insulation. I know what the code is and this is not a house so it does not have to comply.
I am not talking about code....I am talking about the science behind non-vented roof assemblies in cold climates. Check out building science...it has years of studies and information. You don't have any impermeable insulation in your assembly...so warm air is moving freely to the cold roof deck and condensation is forming. Rip out the cotton and replace with Dow or closed cell spray foam.
 

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Discussion Starter · #9 ·
Calling Andy stupid won't get you any help...they are relevant questions...and the type of insulation is most certainly a relevant question!!! You have the wrong type of insulation for your application!
There was not need for that **** he said.
I did not call him stupid, I said the questions were.
The insulation is not the problem, it is the lack of ventilation. I thought you all might be more helpful with this.
 

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If you heat your shop and are in a cold climate, 6" is no where near enough...and if it fiberglass it's worthless in a cathedral application. I think your problem is an improperly designed roof system. Ventilation will not solve your issue if you continue to use fiberglass.
Fiberglass doesn't work on cathedral ceilings?
 

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Waltwood said:
There was not need for that **** he said.
I did not call him stupid, I said the questions were.
The insulation is not the problem, it is the lack of ventilation. I thought you all might be more helpful with this.
Your desire to get an answer you want to hear won't change the answer you need to hear! For non vented cathedral ceiling/roof assemblies, you need a specific amount of non permeable insulation...I.e. Dow or closed cell foam...period! You came asking for help...just because you don't like the answers doesn't mean they are wrong.
 

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Discussion Starter · #12 · (Edited)
I have very moist hot air in the shop attic and I believe I can correct that problem by installing In Vent roof vent low down on the rafters and some form of vent near the ridge and my original post was to get input on what type that should be. I realize my design mistakes and have used spray foam on several jobs, including my current one I am working on, but it was just too expensive for a shop.
How do I post pictures, I want to show some jobs also.
 

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I have very moist hot air in the shop attic and I believe I can correct that problem by installing In Vent roof vent low down on the rafters and some form of vent near the ridge and my original post was to get input on what type that should be. I realize my design mistakes and have used spray foam on several jobs, including my current one I am working on, but it was just too expensive for a shop.
How do I post pictures, I want to show some jobs also.
There are 2 ways to post pictures.

1)http://www.contractortalk.com/f45/how-post-picture-image-36658/
2) http://www.contractortalk.com/f45/how-attach-photo-post-6001/
 

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Why is it impossible to vent the eves?

Does the ceiling have a vapor retarder?

Also, second to why is fiberglass not allowed in cathedral ceilings? If so why do manufactures make r30C and r38C. The C is for cathedral.
 

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Discussion Starter · #15 ·
The rafters tails are false. The main rafters taper down to about 2 1/2" at the eaves, then a 2x and a 1x frieze cover the ends of the rafter tails at the outside of the wall line. Even if you could drill it for a round vent it would not end up at the top of the rafter air space is located. I have it drawn full size on a piece of ply and I will attempt to put it on here.
Thanks,
Walt
 
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