Insulation, Radiant and Vapor Barriers - Insulate inbetween this wall cavity? (pics)

Im remodeling my bathroom and replacing the 35 year old insulation that was quite lacking. On the exterior wall shown in the photos below, there is the wall framing then the "deadspace" inbetween that and the true exterior wall. (I've attached a photo of the home's exterior to show the structure)
Im assuming that this space allows airflow from the attic to escape the house??

My question is, I know that I need to insulate where I have indicated with the BLUE box in the photo, but should I also insulate the area indicated bt the RED box?

Thanks!
Ken

http://www.kpdg.com/images/house/insulate.jpg

http://www.kpdg.com/images/house/insulate2.jpg

http://www.kpdg.com/images/house/exterior.jpg

No. Just the blue area. This gambrel area (i think thats what it is) should be insulated like a kneewall. Make sure you caulk or foam all penetrations into the wall. Also caulk or foam the bottom plate to your overhang. Do the same for the top plate. The floor portion doesnt need to be insulated cause according to the photo it isnt over living space. Put R19 along the wall and cover it with foamboard or housewrap to stop windwash on the fiberglass which will lower its R value. Tape or foam all seams.
Actually it would be way better to have at least R38 here since the wall is exposed to outside temps like your attic. The only way to do it would be to airseal everything like above, put on sheathing for the back of the wall (airseal again) leaving a strip so you could blow in cellulose filling that space completely. Then you could add R13 to the stud bays. You wont have any cold issues after doing all that.

thanks for the reply! I've been holding off putting the room back together until i figured this out. :thumbup:

No problem. I might add that you could use 2 inch pink foamboard nailed to the back of the wall for sheathing. After the seams are taped or foamed you could then easily cut a small hole to blow in cellulose to fill the space. Then add R13 to the stud bays. The board is R10 so that plus the FG will give you a R23 wall at least if you omit the cellulose which is R 3.7 per inch.

good idea! now there is no worry about blocking off venting from the attic with all of this? i can reach up into the top of this cavity and my hand is basically on the attic floor; the attic does have vents on both end walls

Ah well you dont want to block venting. Do you have soffit vents in that section of the overhang? If yes then just omit the part about using cellulose to fill the area but everything else about making a R23 wall stands. If you have none you can go ahead and fill the area if you want as it wont need venting if you seal it up correctly.

well, there are no soffit vents but there is space in the attic where the roof meets this wall but from everything that i can tell (no soffit venting of any kind) i should be safe in filling the area.

thanks again!