Insulation, Radiant and Vapor Barriers - Existing fibregalss in walls

I am in the mist of renovating a 20 yr old kitchen and behind two layers of drywall, I found batt insulation with a brown paper backing stapled to the 2x4. Should I leave the existing fibreglass insulation in the walls if they are dry and just put vapour barrier over it or remove and replace with new insulation? What was the purpose of double drywall as three of the walls are also exterior walls?

If the insulation is full thickness and is tightly fit around elec boxes, studs, etc, I would just leave it and install a vapor barrier. 20 year old insulation should still be good.
As to the double layer of drywall, I can think of only a couple reasons. (1) Maybe the kitchen was remodeled sometime in the past and someone decided to install a second layer over the first rather than repair the old drywall; I've done this myself in the past. (2) Sometimes, due to how close a house is to property lines or adjacent structures, codes will require a fire rated exterior wall. Normally, it would require gypsum sheathing, but who knows what may have been required in that specific instance.
Hope I've helped.

Bruce

Greetings, Imanly

The kraft is glued to the fiberglass (FG) with pitch type adhesive. It is extremely famable. Not someting you'd want by a stove in case of a fire. You probably noticed dryrot at the bottom of the studs, that's caused by the FG condensating moisture and it drains to the bottom. There's a good chance you have mold/mildew growing in there too.

If you can get some radiant barrier single sheet material you can install two layers and dry wall. It will not cause coindensation or deteriorate. It also is superior as a vapor barrier.

Thanks for considering my opinion.