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Duct Insulation

Does your home have air duct insulation in its HVAC system? One of the most energy efficient things you can do in your home’s heating and cooling system is to apply some insulation where it’s most needed.

Think about it; you have countless feet of air ducts running through you house. It all starts at your furnace, then branches out through crawl spaces, basements or garages, then perhaps up walls and through floors and attics. Much of these duct lines run through unfinished spaces. That means, they are exposed to the extreme temperatures that your HVAC is trying to counteract inside your house.

You would think most modern homes that have a heating or A/C installation would have duct insulation applied. This is mostly true, but you’d be surprised at how many homes actually do not have their duct work properly wrapped to both insulate and protect the tubing that is carrying the conditioned (heated or cooled) air you are paying for on your electricity bill. On the other hand, your home may actually have heating duct insulation, but as a home ages, the insulating materials can become damaged or deteriorate from moisture and harsh climate changes year after year.

Let’s take a look how you should go about insulating your ducts in your home’s unfinished spaces. You’ll find that it’s a fairly simple task for the average DIY homeowner.

What you need to insulate and seal your duct work
The materials you’ll need to buy are some R11 fiberglass duct insulation and some metallic duct tape. Both come in rolls and are found at any home center.

For the duct insulation, you can work out a rough measurement of the amount you’ll need for your project. Then, buy a bit more than you think you’ll need from there. As long as you don’t rip open everything when you get it home, you should have no problem returning any unused surplus when you’re done.

The shiny, aluminum duct tape is easy to find too. It’s true that it will cost a few bucks more than standard duct tape, but it will last much longer and perform much better at sealing/insulating seams such as between ducts and return vents. If possible, buy or use a packing tape dispenser. This will make handling the cutting the metal duct tape much easier.

As for your other supplies, you’ll most likely have these on hand: A flashlight, since you’ll probably be working in dark places. Old clothing with long sleeves and pants, since attics and crawl spaces are usually pretty dirty and dusty and not always friendly to elbows and knees. Dust mask, so you can breathe a little easier. Your nose and lungs will thank you later! Gloves and a hat can also help depending on your situation. Also, a few clean rags in case you need to wipe down things before applying tape and insulation.

How to apply air duct insulation
With all your materials and “outfit” donned, it’s time to get started. A couple of tips to keep mind: Ensure that your furnace is set to off and that it has cooled before you start working near it. Start from near your furnace or air handler and go out to the various branches that are within your attic, basement or crawl space under the house.

As you go, simply do the following. These instructions assume your ducts do not have insulation currently, i.e. they never did or you have already removed old and worn insulating materials.

  1. Find each joint (seam) along the ducting. You want to tape these up first to help seal off any small air leaks. Just wipe the area around the seam clean. Also, check that the joints are solid and not coming apart.  Usually, three or more sheet metal screws will hold the joints in place properly. Now, wrap the tape around (one time is enough) and smooth down for a secure hold. You don’t need to be perfectly neat here, just ensure you’ve made a good, tight seal. You don’t want any moisture coming out and damaging the very heating duct insulation you’re putting on.
  2. Next, wrap the duct work with your duct insulation. Get it around the duct, joints, dampers and anything else. Your goal is to cover all exposed metal. Note: if your ducts are actual insulated tubing, you can “double wrap” these if you live in extreme temperatures or you suspect these ducts aren’t quite cutting it.As you complete each section, you can secure the insulation to the ducts using wire. Alternatively, you can use some long 16d nails to “pin” the insulation material to itself, sort of like a using a straight pin on cloth. In other words, don’t just try and tape the insulation to the ducts. Over time, the hold will give and your work will be undone, literally.
  3. For added protection of both your ducts and the insulation you’re installing, you can come back and wrap bubble wrap around everything. This is especially useful in basements where duct work is exposed to contact such as from children or a workshop.

That’s it. One other thing you can do while installing duct insulation is to check that your ducting is attached firmly to joists and other framing members.  It should not be sagging or swinging loosely at any point. When you’re all done you can have the enjoyment of a more efficient heating and cooling system and a lower electricity bill. You’ll be glad you invested a little time and money on duct insulation.

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