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Trying to insulate a roof and an interior wall that used to be an exterior wall

diy_buck | Posted in General Questions on
This situation is a little strange so I’m trying to figure out how to go about it.  The wall at the end of our attic used to be the exterior wall of the house.  At some point, the deck that was on the back of the house was enclosed as part of the house, creating two rooms with vaulted ceilings.  We have added HVAC ducts to these rooms but the upper part of the walls (which are opposite the attic) and the ceilings don’t have any insulation so I am sure that is effecting keeping them comfortable, and we can tell they aren’t as warm/cool as the other rooms.
 
Also, what used to be a gable vent on the end of the house now is a sort of tunnel along the ceiling that runs to the current exterior wall.  When the attic was insulated they blew cellulose in there and it’s about half full.  It’s just sitting on the drywall ceiling so I couldn’t see too well in there without making a huge mess.  Don’t know how well the vent on the now exterior wall works, but the main part of the attic does have two fans.
 
The rest of the ceiling is not insulated and has 2×6 rafters.
 
Knowing that I’m never going to get this perfect, I would like to try and improve as much as I can.  Here are some ideas I’ve come up with:
 
For the attic wall:
1.  Insulating the upper wall from inside the attic.  It is a tight space to work in and there is the blown in insulation to deal with.  Was thinking trying to get foam board attached there but it would be tough.  Maybe a DIY spray insulation kit and just trying to get as close as possible and spray what I can?  Not sure if I should try and block off that gable vent.
 
2. Insulating the upper wall inside the room.  I was thinking of removing drywall from the upper part of the wall and bumping it out to allow adding insulation there.  
 
For the ceiling and ridge vent
I think the best solution is likely going to pulling the drywall down (ugh).  I asked the insulation guy about blowing cellulose but since it’s a mansard/gambrel roof we was worried it would all get blown down into the vertical portion.  He recommended pulling the ceiling and then using baffles to allow air to flow from the other portion of the roof up to the ridge vent.  He said after the baffles I could just use fiberglass batts there.  I thought you weren’t supposed to have batts against the roof sheathing for moisture areas?  Is there a certain amount of space that needs to be left, or is just the baffles enough?
 
I was also thinking about furring out the rafters to get better thickness since 2×6 is pretty slim.  I guess up at the ridge vent I would also want to drop that down to insulate while still leaving the air tunnel to allow for breathing.
Here are some pictures: https://imgur.com/a/FUoL8tU

So, not really sure which direction to go in, but I figured everyone here would probably have some great suggestions.  
 
Thanks so much!

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Replies

  1. diy_buck | | #1

    Thought I would bump my question since it didn't get any responses yet. It's also pretty confusing and long winded!

    Some other thoughts I've had since (usually lying in bed staring at the ceiling...):
    1. Maybe pull down the ceiling drywall then spray foam? I think I would need baffles to keep the air flow from the sides of the mansard roof. With 5.5" rafters minus baffle space, maybe 4" of spray foam? ~R28? Better than the current R0. Would need to figure out the gable vent area and try and talk the foam guy into climbing through the attic to do the extra wall.

    2. Would it be better to just remove ceiling drywall and upper wall drywall and drop the ceiling level? Not sure about weight issues if it's suspended from the rafters and/or ledger boards around the room. Or I've seen those metal grids that can hold drywall. After drywall, I could leave an access panel then just have cellulose blown on top? I'm know this will also add weight, but drywall usually holds blown in up, right? Then the whole upper parts of the room would just be attic space, which is fine. Easier drywall install too.

    Thanks again for any help! And please let me know if any more pictures, diagrams, info, ramblings, etc., would be useful!

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