If you are going to remove the existing siding you might want to strip the exterior down to the studs and install new plywood or osb sheathing followed by plastic housewrap and new siding.
Best insulation for garage wall with siding.
If you cram too much insulation into a wall that is too thin you reduce the insulation s air pockets and thus reduce its ability to provide thermal resistance.
If you already have drywall installed around your garage but don t have it insulated then blown in insulation may be the answer.
Exterior walls and floors.
Sturdy wood sheathing wood sheathing such as plywood or oriented strandboard osb represents a simple yet economical finish option for garage walls.
Measure and cut the fiberglass batt for an exact fit.
Check garage walls and ceilings that are adjacent to conditioned spaces.
The most popular flat foam insulation products used in remodeling are made of expanded polystyrene eps extruded polystyrene xps and graphite polystyrene gps.
There are other options of course.
You can learn more about these insulation types here.
Fiberglass insulation works partly by trapping air pockets within the insulation.
Since your wall lacks an exterior air barrier the best insulation to choose in your case would be spray polyurethane foam.
It can be fastened directly to the wall.
When doing it from outside the job involves removing some siding panels so that large holes can be bored through the sheathing at the top of wall stud cavities.
So before insulating go around the garage with a can of low expanding spray foam and seal all gaps and cracks that let in the daylight.
Find your zone on the map and then use the chart to determine the level of insulation you need to properly insulate your attic walls floors and crawlspaces.
Then installers use special equipment to blow fiberglass fibers or cellulose insulation through the holes into the cavities.
Achieving greater r values in attics the higher the r value the better the thermal performance of the insulation.
Turn off the electricity then remove an electrical outlet cover for a view of exterior insulation.
A thick down filled jacket or sleeping bag works the same way.
You can insulate the walls ceiling and door of the garage to the highest r value possible but if you fail to fill those air gaps you ll still be wasting a lot of heat.
Check behind knee walls which are walls between living spaces and the garage or attic.
In addition flat foam insulations can help level out inconsistencies in the wall for a more perfect siding appearance.