Re: no insulation on outside walls
There are a myriad of methods employed and materials used.
For example .... using the conventional fiberglass batts you would need to remove the interior walls if applied from the inside .... or ....installing from the outside remove the exterior siding and install the fiberglass batts.
There are other options like blown in cellulose of fiberglass. This method would simply have strategic holes drilled and with an applicator hose inserted to blown in the insulation. Or ... there is injection type of foam insulation .... similar to the blown in method.
Attach rigid sheets of foam insulation to interior walls then cover with new drywall.
Rigid sheets of foam insulation can be applied to the exterior with a new exterior siding finsh applied.
You might check with your local building department as to suggestions and requirements ... such as a vapor barrier.
Hope this helps.
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