DIYing fiberglass ductwork insulation can be a bit of a mess—but if you’re suited up and ready to try it, here’s how
Well-insulated ducts are efficient ducts—which means a lower number on your electric or gas bill when the time comes. (Plus, in some areas, builder’s code may require you to insulate your ductwork.) But some kinds of insulation can degrade over time, requiring eventual replacement. Or maybe you’ve just installed a brand-new duct system and are hoping to DIY the insulation process! If so, it’s time to learn how to insulate ductwork yourself.
Be aware that this can be a finicky job, requiring precision, patience, and—since you’ll be working with fiberglass insulation, which can carry dust that’s harmful to breathe or get in your eyes—some protective gear.
If all that sounds handle-able to your handy self, let’s get started.
No matter the project, safety always comes first, which is why this is the first step on the list. Fiberglass dust can be harmful to your eyes, skin, and lungs, so it’s important to protect yourself.
To safely work with the fiberglass insulation you’ll be using to wrap your ducts, you’ll need to invest in—and don—a long-sleeved shirt, socks that fully cover your legs, thick, sturdy gloves, goggles, and a dust mask or respirator. Make sure when you choose a mask that it’s one specifically designed for use with fiberglass dust. Some certified N-95 masks will work, as will half- or full-face respirators with a P100 rating.
Once you’re geared up, it’s time to get started. Start by turning your system off. Then, head to the attic or the basement—wherever your ductwork lives—and take a look at the existing situation. Perhaps there’s already insulation covering some or all of the ducts; perhaps the ducts are bare and ready for brand-new insulation.
If some or all of your existing insulation looks to be in good shape, you may want to leave it where it is—though doing so will make it impossible to check your duct system for leaks, so you may be missing out on energy savings. Otherwise, the first step will be to remove and dispose of all your old insulation. You may be able to simply peel off the tape holding the insulation to the duct, or you may need to carefully use your utility knife to assist you. (Exercise extreme caution if you have flexible or semi-rigid ductwork, which is more prone to tearing and leakage than sheet metal ductwork.)
Because fiberglass can be a health hazard, it’s important to put all of your existing insulation into sealed garbage bags before disposing of it. Check with your local dump and household waste recycling centers; some may be able to recycle old fiberglass insulation.
Once your ducts are visible, you can use the opportunity to check for leaks and repair them. Turn the system on a low setting, and feel your way along the ducts for any air leaks. You can use a tissue for this part. Hold the tissue against the ducts and see if it starts moving. If it does, you have a leak. Leaks are more likely along joints and bends in your ductwork, so pay special attention to those areas.
Once you’ve spotted the leaks, keep track of them, and then, after turning the system off again, use metallic foil tape designed for sealing ductwork to seal them. (Hilariously, duct tape is not actually the right kind of tape for HVAC ducts, as the adhesive will melt under extreme temperatures.)
Depending on the type of ductwork you have and the extent of any leaks there are, you may also need to use duct mastic, or sealant, which is applied with a paintbrush. Even if you don’t find any active leaks, duct mastic can help ensure your ductwork is tightly sealed and as efficient as possible. Ensure the sealant has dried thoroughly before moving on to the next step.
Once your ducts are sealed nice and tight and any sealant you’ve applied has dried, you can get started on the fun part: getting the insulation ready! Using a square and a sharp utility knife to ensure a tight fit around joints, particularly if you have rectangular ductwork, mark out and cut your insulation to fit your ducts.
Note: The insulation you buy should have an R-value, which is a measure of its insulation rating, that conforms to your local building codes. (This may be R-6, for example, or R-8.)
Now that everything’s set up, wrap the insulation around each duct. You want it to fit snugly but not so snugly that the fiberglass insulation is compressed. Use short pieces of foil tape to hold the seam together, pinching it first to ensure a tight fit and no leaks. (Peel the foil tape off its backing a little at a time to avoid having the tape stick to itself.)
Once the insulation is taped well enough to stay in place, add another layer of lengthwise foil tape along the seam to reinforce the seal. Where two pieces of insulation join, wrap tape all around the entire edge so there’s nowhere for heat to escape. This is also important for ensuring that moisture stays out of your insulation and doesn’t end up condensing on your ductwork.
Continue to move through your duct system, wrapping each duct and taping it shut, ensuring the insulation fits tightly and has no gaps. Once it’s all in place, stand back, take a deep (masked) breath, and enjoy your handiwork—and, once they come in, your lower energy bills!
While DIYing your ductwork insulation is definitely possible, for many people, it might be a bit of a challenge—or just too much of a mess. You will definitely save money on labor costs by DIYing, but working with fiberglass is inherently risky. In either case, your local duct installer will be happy to help.
The short answer is yes—and the long answer is yes, but it takes some care and precision. While insulating your own ductwork isn’t the easiest home improvement project in the books, it’s not the hardest, either. You’ll need the right gear to safely handle fiberglass insulation, as well as the patience and precision to cut the insulation to fit your ductwork. All in all, the project could save you money on professional labor and energy costs down the line.
Because it doesn’t degrade as quickly as natural insulation materials do, many home experts recommend using synthetics, like fiberglass insulation, to keep your ductwork as efficient as possible. (Although other materials, like mineral wool, can be used, fiberglass is considered by many to be the most widely available and effective option.)
Some builders’ codes require ductwork to be insulated, though specifics will vary depending on other factors about your home, what kind of HVAC system you have, and which type of ducts are used in your system. That said, insulating your ductwork can go a long way toward improving energy efficiency and lowering your energy bills over time, as well as keeping your HVAC system working—and, therefore, keeping your home warmer or cooler.
