2 yards of felt backed vinyl. Covers the whole windshield. Got grey to match the car. Need to get red for the truck. Tends to cost a bit more, but looks good. Placing cardboard or aluminum flashing under the wipers defeats one of the primary ways the windshield stays clear: cowl heat from the engine. Where is your air intake? draws air from the cowl. If that's covered in snow, you'll never have a clear windshield.
Cover the windshield, cover the wipers, cover the cowl. Three fold bonus: clear windshield in all temps and precipitations, clean wipers should you need them, and heat is radiated up through the cowl to further heat the windshield (you did leave it on while cleaning the snow right?)
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