Spray affected plants with a ready-to-use systemic insecticide that contains acephate, imidacloprid or dinotefuran. Systemic formulas do not kill bagworms directly. The active ingredient is absorbed into plant leaves and needles, and then circulated throughout the plant. The insects die when they feed on plant parts and plant sap.
Depending on the size of your garage, insulating the walls with batts of R-13 will typically run you about $400, the ceiling $600, and the garage door will cost about $600 if you do it right (See image to the left). You can use the pink Styrofoam stuff from Home Depot, but that will only insulate your door to about R-6.
Non foam backed vinyl siding typically costs betweem $.60 and $1.25 per sqaure foot. Insulated or foam back vinyl siding will run $1.25 to $2 per square foot for the panels only. Vinyl shingles, which are typically much thicker and more robust, are more expensive and will run $2 to $3 per square foot.