Insulation in kneewall


I have two questions. The first is the technical term for the area I describe. The second is the correct insulation treatment for that area.
Our home has sloped ceilings and knee walls on the second story, along with a shed dormer. The dormer provides lots of space to utilize the two bedrooms and bath on the second story. The floors of the unused, uncoditioned knee walls are directly over first floor conditioned spaces, so they are insulated with blown in cellulose insulation between the joists. There is no floor inside the knee wall, just exposed joists, no deck.
Two walls in the knee walls are adjacent to conditioned space in the bedroom. The roof sheeting is overhead, down to the fascia at the header. My question has to do with the other wall, an exterior wall. It is a gable end wall of the house, a 2 x 4 stud wall that pitches from the lowest part of the roof up toward the gable.
The plate of this wall rests on the plate of the first floor exterior stud wall. Directly mounted across these knee wall studs is the first joist. Now you have a "pocket;" that is: exterior wall is back of pocket, two vertical studs are the sides, horizontal plate is the bottom and first 2 x 10 joist is the front.
The blown in cellulose was placed in the "pocket." Lifting that, we find frost on the second story plate. Remember, this knee wall is over conditioned space. The exterior wall of that conditioned space is fully insulated under the drywall, as is the ceiling (floor of the kneewall).
Question: What is the technical term for the "pocket" described above? Should that "pocket" be insulated or not. (Frost tells me not, but I want to be sure).
Thanks.
Susam
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your post is rather confusingly worded which may be why no one else has responded.
The wall below a dormer is a dwarf wall, the sides are the cheeks. If you are asking about the triangular space behind the dwarf walls it is simply an unheated void. As that void is partly over the ceiling below then it should have 270-300mm insulation quilt or 140mm Celotex over the ceiling, as you have some blown insulation there simply top it up with the B&Q 200mm quilting made from recycled plastic bottles. The dwarf should have insulation behind it. Re the 'gable end wall' as you put it; if it's the dormer cheek then it should be insulated internally. If you dont want to rip off the decorative face then simply fix thermal plasterboard over the top.
AJ
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