Older, non insulated cylinders lose a considerable amount of heat and are likely to have buildup of limescale, which reduces efficiency and makes longer heat up times. Even insulated cylinders over 10 years old lose more heat than modern ones. Unvented cylinders have been designed to offer significant performance improvements over regular cylinders. They combine rapid re-heat times with high heat retention and are guaranteed for upto 25 years depending on make and model. They also come in a wide range of capacities from 90-300 litres to suit any property.