Pipes often transport water that is substantially warmer or cooler than the air or material around the pipe. High-performance pipe insulation is particularly important since heat loss or gain is greater when there is a large difference in temperature of the water in the pipe and the temperature of the air or material around the pipe. The rate of heat transfer (loss or gain) is greater when the temperature difference is greater. Water heaters typically produce water that is around 135○F, but pipes may pass through areas ranging in temperature from 0○F to 70○F. The big difference in temperature results in great heat loss when pipes are uninsulated or under-insulated.