How to Install Fiberglass Pipe Insulation

Lead Image for How to Install Fiberglass Pipe Insulation
  • 1-2 hours
  • Beginner
  • 20-35
What You'll Need
Fiberglass pipe insulation
Sharp utility knife
Marking pen (optional)
Tape measure
Length of pipe to be insulated

Fiberglass pipe insulation, when fitted correctly, can help to make a piping system more energy-efficient and prolong the life of your water heater as well as the plumbing system itself. Installing fiberglass insulation is a simple DIY project that can be accomplished with a few basic tools and some attention to detail.

Decide Adhesive Type

Fiberglass pipe insulation comes with two types of adhesive, either single-back or double-back. Both have a layer of paper on the outside that you simply pull away when fitting it to the pipe. Single-back adhesive simply attaches to the pipe, and a double-back adhesive has two bands of adhesive that stick to each other when the insulation is fitted over the pipe. Many DIY'ers find the single-back insulation easier to work with, but either will work for this project.

Cut Insulation to Fit

First, measure the length of the pipe you are insulating and cut a length of fiberglass insulation to match. Note any valves or T pipes branching off from the main pipe since you will need to cut holes for them in the correct spots on the insulation. Measure any vertical pipe leading to your horizontal pipe if this applies, then cut a second length of fiberglass insulation to fit this section as well.

Cut Valve Holes

Hold the horizontal length of insulation against the pipe section and mark where you will cut out the sections to be fitted over valves or smaller T sections of pipe. You can use either a marking pen or you can simply make small slits in the insulation where these areas will be. Use a utility knife at least 5 to 6 inches long; an old kitchen fillet knife that has been sharpened also cuts fiberglass insulation quite well. Cut holes large enough to fit, then cut slits from them in the paper backing so that you can get the insulation around the valves and T pipes.

Cut Out Space Inside Insulation

Once you have cut valve holes in the top of the insulation, you will need to open it and clear some space in the fiberglass so it will fit properly around the valves. Fiberglass insulation sections open into halves; simply find the valve holes and carefully cut away some layers of fiberglass underneath them. Do this a small layer at a time, since it is easier to cut too little than to have cut too much.

Fit Insulation Around Pipe

Work your section of fiberglass insulation around the pipe section with the adhesive strip facing you. Make sure it fits securely, and trim any extra fiberglass around the valves if needed. Peel away the adhesive strip from the paper backing and stick it to the front section of insulation. Pull the adhesive strip gently toward you as you do this, in order to have an even and smooth fit. Be careful not to tear any of the paper backings.