Attic space construction question

[Back2class]

I have an attic room I want to make into a bathroom. My question is about insulation. Sheetrock will be nailed directly to the roof rafters and it will create a nice cathedral ceiling. I have to put insulation in and was wondering what the right way to do it is. It has ridge venting.

I know there needs to be an air gap between the underside of the roof sheathing and the roof side of the insulation. The moisture is the issue here.


I have herd of using faced r-11 turned backwards so the non faced side faces the interior and leaves a 2" air gap between the insulation and roof plywood. I have also herd of using those foam box outs to create airflow under the roof with thicker unfaced insulation.

Wouldn’t both of these ways of insulating create moisture problems in the insulation?

I am leaning towards using r-11 unfaced like you would in a flat ceiling. That leaves a gap behind the insulation for air to flow up and out the ridge and may solve the moisture in the insulation issue.

Another person suggested using faced like you would in a wall to keep moisture out completely, buy wouldn't that create a very damp room?

I am really lost here and need to get this right. Its a 6:12 roof pitch by the way in north GA.

 

[BONE]

pm sent

 

[lagrangedave]

Put the faced insulation with the paper toward the heated area. Insulation doesn't stop air flow it just slows it so there are not large temperatue losses or gains. It will wick enough to eliminate moisture. Do not stop up your ridgevent though.

 

[hunter_58]

get an r=19 min r=30 preferred, with air space
good luck

 

[silvertitan]

go to lowes or home depot and ask for insulation baffles. install them against the roof sheathing with a staple gun and install insulation as normal. with the kraft faced side towards the living area.

 

[Parker Phoenix]

get an r=19 min r=30 preferred, with air space
good luck

Depends on the rafter size. You can't use R-19 in a 2x4 because compressed insulation does not work as well, if it's a 2x4 I would use R 13 with a Paper or foil face.

 

[flyingt]

use polyvents against the decking first. These are the egg crate material things that are about 4 foot long and these allow airflow from soffet to ridgevent. Also make sure you put the paper towards the heated space, and do not compress the insulation, meaning get the right thickness. They also amke a high density batt insulation and you will be able to get a higher r-value out of a smaller thickness. I can answer some more questions if you want. I am an insulation contractor so I might have a little experience.

 

[Havana Dude]

Moisture?

Never heard of a moisture problem in an attic. i could see possibly having one if the attic is not ventilated properly though.

If you were to do as you have planned, how much of the attic would be cut off from the ridge vent, if you just stapled up the ins. and did not worry about air flow? If the space is not cutoff from the rest of the house, you could possibly install an power attic vent, to allow for the air in the cutoff space to circulate. Do you have vented soffit?

 

[Back2class]

ridge vent.

Thanks guys. I knew I would get the right answer here.