How To Insulate Ductwork [Inc. In The Basement Or Attic] –

1. Inspect your Ductwork for Size and Form

The first step in insulating your ductwork is to inspect your entire system. Usually, there are ducts only in either the attic or basement/crawl. However, some homes have ducts in both locations. Often, accessing these ducts requires movement in dirty and cramped locations.

Click here for a protective suit from Amazon.

Therefore, it is wise to wear proper protective equipment when performing the inspection and the subsequent work and only enter safe spaces. Wear full-body suits, breathing protection, eye protection, and gloves (optional).

During the inspection, have the fan of your HVAC system running. This allows you to feel for areas that are leaking air out of your ducts. Overall, look for and note the following during your duct inspection:

  • Diameter/Perimeter
  • Length
  • Air leaks (and length of leaky duct seams)
  • Location

Diameter, length, and air leaks are information that allows you to plan for which and how many materials you need for your project. The location of your ducts enables you to prepare for how to accomplish the duct insulation and whether your ducts even need insulation.

As you perform your inspection, be sure to note the diameter/perimeter and length and the specific lengths of each different size of ducting. Usually, a single home will have two or more different-sized ducts throughout the system.

Remember, if the task appears too daunting, it is always possible to call weatherization professionals to provide a bid and do all of the duct insulating work for you.

Does exposed ductwork need to be insulated?

Exposed ductwork needs to be insulated if it is in unconditioned space. On the other hand, if the ductwork is in a conditioned attic or basement, there is no need for insulation.

Any heat or cold that escapes from ducts in conditioned spaces escapes to already heated or cooled locations. This means that jacket losses in conditioned spaces are not energy inefficient or costly.

What type of insulation is used for ductwork?

According to the North American Insulation Manufacturers Association, fiberglass insulation is the standard for duct insulation. For at-home remodel applications, you will want to use foil-faced fiberglass batts with an R-value over R-6 for all duct insulation.

Click here for foil-faced fiberglass batts from Amazon.

However, for ducts within the belly of mobile homes, surrounding the ducts with loose-fill insulation is standard. Further, for attics that have ducts very close to the ceiling, it is sometimes the most practical to blow loose-fill insulation over the top of the ducts and over the ceiling in one go.

Foil-faced fiberglass batts are the best option because they are easy to install and the foil acts as a moisture barrier that stops condensation on the duct surfaces.


Why Foaming Ductwork is Needed

Over time houses move and shift, and the old, hard ducts become disconnected and insulation falls off of them. We want to remove all that old insulation and foam the duct. What this means is that we spray a layer of foam insulation all around the hard duct, all the way down. We’ve found that this does two things. First, it insulates the duct work much better than any padded or fiberglass insulation ever could. It also seals it. There is nothing better, thermally speaking, than an air seal plus insulation. There’s nothing better for protecting your duct work that’s delivering that cold air through your house.

Ductwork Insulation in Different Locations

How to Insulate Ductwork in Attic

To be completely honest, you should try to avoid installing ducts in a vented unconditioned attic. In case ‘the damage had already been done’, move the ducts inside your home’s thermal envelope.

Your home has ducts in the attic if there are vents in your ceiling. And in case you are planning on leaving the ductwork there, then you would definitely need to insulate the system.

Installing insulation in unconditioned areas might be a bit tricky as you need to avoid ‘sweating’. Due to the drastic temperature changes, condensation might appear on the ductwork and that is something that must be avoided at all costs.

The first thing that you have to do is find and repair any leaks. After that, you can begin insulating using one of the methods that we have already mentioned above or you can try going for blown-in cellulose insulation: 

  • Ensure that the ducts are located on top of the rafters.
  • Use a quality hose and blowing machine.
  • Try to fully cover the ducts with cellulose.
  • If there are any uncovered areas left, you can use insulating blanket material.

Insulation Around Ductwork in Ceiling

There are quite a few disadvantages to having ducts in the ceiling. Heat rises and if it starts in the ceiling, it doesn’t really have anywhere to go. As a result, you are using your furnace inefficiently. 

However, if you have ducts in the ceiling and you know that the space is well-insulated, there might be no need in insulating the actual ductwork

Should I Insulate Ductwork in Basement?

The main thing that you should bear in mind is that insulating the ductwork in the basement will make the space much colder. If you have plenty of drains and water pipes running through the basement and you live in an area with super cold winters, then the pipes might freeze and burst in the winter.

To avoid that, you can use an electric heating tape wrap and apply it to the pipes. Or you can consider insulating both the basement walls and the ducts.

Insulating Ductwork in Crawl Space

Just like your attic, the crawl space is an unconditioned area with great temperature fluctuations. You should definitely install furnace ductwork insulation as this will help you save energy and money (including cash saved on furnace maintenance and repair). Insulation, if installed properly, also does a great job at preventing condensation.

You might want to consider hiring a professional to insulate your crawl space as it is challenging to work in such a tight space. 

The most common type of insulation used for the crawl space includes foil-faced blanket and spray foam insulation.

5. Enjoy the Added Comfort and Savings

Congrats! You are all done. The money saved on energy cost through duct insulation and duct air sealing is usually fully realized over the life of the measure. Duct insulation is considered an excellent investment.

Your Next Step

You can learn more about our ductwork services here: Air Duct Services! Very shortly we will have up more information on duct work, sealing, and foaming. We’d love to talk to you about any part of our service, and give you an estimate. When we come out to you we will assess your whole attic space to see what shape your attic is in and which part of our services will be appropriate for your space, including radiant barrier, removing and replacing insulation, duct work, etc. Give us a call, we’d love to see how we can help your home be more comfortable for you!

Insulating Ductwork – What Tools/Materials are Needed

The following tools and materials are needed in order to install ductwork insulation in your basement, attic, and/or crawl space:

  1. Goggles
  2. Dust mask
  3. Protective Clothing
  4. Gloves
  5. Laser Thermometer
  6. Mastic
  7. Caulk Gun
  8. Duct Tape
  9. Foil Tape
  10. Masking Tape
  11. Paint Brush
  12. Silicone Tube
  13. Box Knife
  14. Fiberglass Insulation (foiled backed, heat resistant, the higher the r-factor, the better)

** Depending on the type of insulation you are using and what area you are working on, the materials may vary.  You might not use all the materials listed, but they may come in handy at different times during the installation of your insulation.

Why Should You Insulate Your Ductwork?

We mentioned energy efficiency by reducing energy loss through uninsulated ductwork when heating and air conditioning your home. Ecofriendliness shouldn’t be overlooked. The more energy that is conserved or saved, the better it is for the environment.

Plus, the fact your equipment won’t work as hard to keep your home comfortable.

It’s also true that if your HVAC system is properly sized but you’re losing a lot of the treated air with uninsulated and possibly leaky ductwork, your furnace, heat pump or AC might not be able to keep up, and parts of your home won’t be adequately heated or cooled.

OK, we’re all on the same page now. Let’s talk about how to insulate ductwork in the basement or attic.

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