Insulating pipes and ducts that run through unheated space will result in a significant savings in your energy bill. Heat escapes from bare hot-water pipes causing the water sitting in those pipes to cool down between uses. This results in running extra water from the faucet to get hot water. Wrapping these pipes will save you money. Wrapping cold water lines won't save you energy dollars, but will eliminate dripping and sweating from condensation, avoiding water spots.