Insulating pipes prevents freezing in cold spaces and reduces heat loss from hot-water lines, so hot water arrives faster and the water heater works less. It's a cheap, quick DIY job.
Where to insulate
Focus on pipes in unheated areas — crawl spaces, garages, attics, and against exterior walls — where freezing is a risk. Insulating accessible hot-water lines also saves energy and speeds hot water to the tap.
Choose the material
Foam pipe sleeves (split tubes that slip over the pipe) are the easiest option and come sized to common pipe diameters. For tight or irregular spots, insulating tape works. In high-heat areas near a water heater flue, use materials rated for the temperature.
Install it well
Slip the foam sleeve over the pipe, seal the seam and joints with the adhesive strip or tape, and cover elbows and tees too — gaps let cold reach the pipe. For freeze-prone runs, pair insulation with other measures like a dripping faucet and sealing air leaks.