I have a 50 year old house with pratically no insulation left. I have a question about the insulation between the side attic and the top attic.

The side attic is 40' long, with 10 inch joists, and a 4 foot knee wall. I'm going to seal off the joist space that leads under the living area, use R13 insulation on the knee walls, R30 insulation between the joists, and add a radiant barrier (perforated) along the rafters and over the knee walls [over the insulation].

The TOP attic is also 40' long, with 6 inch joists, and is 12 feet wide. I'm adding radiant barrier, and using two layers of insulation (R19+R13).

Between the SIDE attic and the TOP attic, along the rafters, there is a 5 foot slanted section of that is part of the interior room's ceiling. It looks like it has R13 (3.5") insulation with a foil backing on both sides of the baffle. It is in very poor state, including tunnels created by squirrels that lived in the attic for years (I just bought the house).There is no plastic baffle to ensure good airflow from the side attic to the top attic, although there IS some air flow.

Am I better of just leaving it as-is? Removing it and trying to re-insert something sounds like it would be a nightmare, but I'm thinking that no amount of insulation on the top and side attics will make up for the heat that will slip in through this section of the ceiling.

Any suggestions? This is Texas. We hvave 40-60 days of 100+ degree heat each summer. I include a picture of the insulation in question. I've pretty much removed all the other insulation. I've included a picture of the insulation in question.