Freedom Pet Pass^® insulated dog doors work differently than conventional pet doors. They use patent-pending M.E.S.S.A. technology to maintain an airtight seal every time your dog passes through the dog door flap - sealing 190% better than the leading pet door brand. With no air leakage you will reduce carbon emissions and save more money in energy costs. And unlike ordinary pet doors, they prevent rainwater, snow, insects, and snakes from entering your home. Invest in the only brand of insulated dog doors that Energy Star Partners, Certified Green Home builders, and ultra energy efficient Passive Home Builders recommend for your home.