Attic insulation question...

[Richard]

I'm working in Florida right now so I'm simply working as a middleman between my wife & keyboard...

Scenario: Seems my sister in law did some changes in her house (her brother who lives out of state did the work when he was living in the area)

House built perhaps in the 60's (just guessing)

In the kitchen, they removed all the ceiling drywall. I don't know what was above the drywall but from what I understand they then raised the ceiling level and essentially put new drywall on the roof itself, as in, mounted the drywall to the underside of the roof. (I asked for pictures becuase I'm sitting here wondering what happened to the horizontal joists that might have been in the ceiling)

I don't even know if that part is important to the question.

Seems they took pink insulation, mounted it directly to the underside of the plywood that makes the roof. They then mounted the drywall on the other side of the insulation.

Seems there is no venting space in there and now she's had some condensation form and a portion (all?) of her drywall needs to be replaced on her ceiling.

It's possible that it's a leak for all I know.

I asked her if someone could take a picture of the ceiling and perhaps... a before picture and/or a picture with some drywall removed (if they exist) to at least put some visuals into the conversation. No luck so far.

So the upshot is, if you have your roofing plywood with insulation butted up agasint it and your drywall butted up against the insulation, is it reasonable that you've created a problem and if so, would they have been better off using something like a foam-board / hard insulation instead of the pink Owens Corning style?

Given how the wife described it, I'm presuming to fix it right, the ceiling will have to be pulled down, reinsulate and reinstall new drywall.

Thoughts given the minimal details?

 

[jpm1]

You are discribing a cathedral ceiling which is the hardest roof to vent! No matter how you look at it there MUST be a space between the insulation and the underside of the roof deck, proper soffit and ridge vent. Personally i would go to CertainTeed and see what they have to say. call their toll free number and talk to their reps. There good to work with, were one of their distributors. good luck . . . John

 

[ustmd]

Yep--the attic space is not vented well enough.

They can either redo the venting or convert it to a "hot roof"--which works well in areas without snow.

BSD-102: Understanding Attic Ventilation — Building Science Information

 

[radioman]

you are guessing exactly as much we are. as you surmised- you really need to have airflow on that roof.

 

[Tig]

J

So the upshot is, if you have your roofing plywood with insulation butted up agasint it and your drywall butted up against the insulation, is it reasonable that you've created a problem and if so, would they have been better off using something like a foam-board / hard insulation instead of the pink Owens

Yes, a 2" air gap, vented top and bottom would be the minimum. IMO

 

[Ed of all trades]

Without proper venting you can rot your house down, grow mushrooms on your rafters, mold, fungus ect. This is not a fix in a couple of years thing. Fix it soon. By the way, I have been in houses that have had all of those problems. A cathedral ceiling is framed down from the rafters on a lower pitch, not hooked to them.

 

[sdkubota]

I have a new home with icenene insulation (spray on foam). The underside of the roofing decking was sprayed with the foam directly known as "hot roofing". I investigated it some before allowing it to happen but it turned out to be an acceptable method with that insulation type. No air flow whatsoever.

 

[dave1949]

I have a new home with icenene insulation (spray on foam). The underside of the roofing decking was sprayed with the foam directly known as "hot roofing". I investigated it some before allowing it to happen but it turned out to be an acceptable method with that insulation type. No air flow whatsoever.

The foam is also the vapor barrier as I understand it. Including attics in "conditioned space" is becoming more popular. Since the foam seals the underside of the roof sheathing, it seems like condensation at that surface would not be a problem.

 

[Dr Dave]

They make styrofoam vent shoots, that you staple to the plywood before installing insulation. You may want to lower ceiling some to allow more insulaton. Spray foam is an option, but may effect airflow for the rest of the house and will shorten shingle life on that section of the roof.

Dave

 

[ENG18LT]

Rich, Three possible issues here.

1-roof leaks causing the water spot.
2- No baffles were used prior to insulation, Fiberglass does not create enough of a vapor/air barrier to use without proper ventilation. Done right there should be vented soffits, continuous baffles to the ridge and an adequate ridge vent. If you don't do this you will have mold problems. Doing this method significantly reduces the insulating value of your envelope. I am guessing that the rafters are 2x8 from the age of the house (could be different), if they are with baffles that leaves only 5 1/2" of space for insulation. With fiberglass the max you can put in there is R-21. I don't what the minimum R-value is for your area but this may not be enough, not even close for our climate in NY.
3-Collar ties/ceiling joist removed. This is a structural issue, they not only are used to attach the ceiling to, but provide structural stability to the roof system. They counter act the forces applied to the outer walls, preventing them from bowing out. Removing them is just asking for trouble down the road.

Solutions-
1- have roof inspected/fixed

2- Pull ceilings and insulation. Have closed cell foam sprayed full depth between rafters. This will provide excellent R-value and a very good air/vapor seal. Just make sure it is closed cell and not open cell. Then you can attach new ceiling.

3- Install collar ties no higher than 1/3 the vertical height of the rafters creating a raised flat ceiling, or tear off the whole system and install scissor trusses for the cathedral effect.

Good luck.