Existing insulation and drywall are in the basement walls, probably original build. Some parts only half the wall.
Can I build a 2x4 wall in front of that and insulate with roxul.
Under the previous Code basement walls were only required to be insulated to 2' below grade and R-12 was more than enough. With the recent introduction of Energy Codes that has changed and insulation value has to be determined as an assembly including the studs - typically R-20 now for the full height.
One choice is to install 2" of rigid insulation to the lower half of the wall that is presently uninsulated, then 2 x 4 framing plus R-12 or 14 batt insulation should satisfy the requirements. ensuring vapor barrier is on the warm side of the insulation.
I would tear out everything that is there and start over. It is important to see the block wall underneath to ensure there are no air or water leaks, before covering everything up forever.
This will ensure that all of the work and finishes to come afterwards will not be at risk.
Then install the 2x6" stud wall and R20 insulation and 6 mil vapour barrier. Be sure to use the blue rot-resistant bottom plates from Lowes, wrapped in vapor barrier.
Par-Tek Design Build Ltd.
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