Should ductwork be insulated in a crawl space?

Does Ductwork Need to Be Insulated?

When talking about ‘ductwork’, we are referring to the system of pipes and ducts that circulate cooled or heated air throughout the house.

Unfortunately, the absolute majority of ducts are made out of thin material (fiberglass or sheet metal) and that’s why the air that is traveling through the system can easily get lost. 

Of course, you can always choose to not insulate the ductwork in your home. But adding insulation to the system has quite a few benefits that you should know about:

  • Reduced energy consumption ; lower electricity bills

Insulation helps ensure that the air that is traveling through the system stays at the desired temperature. Moreover, it prevents leakage which, in its turn, leads to energy loss.

In fact, without proper insulation, you can be losing up to 30% of the energy that is used to heat or cool your house.

Tip: to find out if your ductwork needs additional insulation, place your hand close to the supply register. The answer is ‘yes’, in case the air feels lukewarm.

  • No condensation

Whenever cool air passes through a very warm part of your house, it may cause condensation to appear in the ductwork. As a result, there will be moisture build-up that can lead to mildew and mold growth, and other problems.

High-quality insulation can prevent condensation from occurring in the system.

In a nutshell, ductwork insulation will help ensure that your home stays cozy and at an optimal temperature. And all that – without the cooling and heating systems having to work at full capacity all the time. 

But does all ductwork need to be insulated? Or are there certain areas where insulation is more necessary?

How does insulation work?

Insulation traps pockets of air to slow the movement of heat going in and out of your home. The rate in which the heat is slowed is measured by an R-value.

The goal is to envelop your home in thermal protection to keep you comfortable all year round.


Is duct work covered by insurance?

Is Ductwork Covered By Insurance? No, your homeowner’s insurance will not cover ductwork, cleaning, repairing, or replacing it. … The efficiency of your HVAC system can be affected by the ductwork and it can put your home in jeopardy if problems are not caught and addressed.

How often should ductwork be replaced?

Like all HVAC equipment, air ducts experience wear and tear, which is why it is important to have your ductwork checked and likely replaced every 10 years or so.

Ductwork Insulation – Details

Types of Ductwork Insulation

Fiberglass is the most common material used for ductwork insulation. It comes in a flexible or rigid format and has R-values that range from R-4.0 to R-11.

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Flexible fiberglass is wrapped around the air ducts. After that, the outer backing is backed by foil. On the other hand, rigid fiberglass is great for rectangular ducts. To keep the rigid board against the ductwork, experts use clamps and clasps.

Sometimes, more than one type of fiberglass can be used in a single system.

Such insulation prevents condensation, helps conserve energy, and provides temperature and acoustic control.

The second widespread type of insulation is made out of polyethylene bubbles that are located between radiant barriers (they look similar to simple foil). It is a cheaper option that is relatively easy to install. 

However, do bear in mind that in order to take advantage of the barrier, you would have to leave 2 inches of air space between the duct and the foil. And that is not always a simple thing to do. 

Foil-backed self-adhesive foam duct insulation is easy to install and can be wrapped around irregular ductwork. The material is relatively thin, but it dampens sound very well and, if you ever need to, can be used with other types of insulation.

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Warning! Make sure to use only the foam that is specially designed for insulating as a lot of foam products can become toxic when burning and are highly flammable.

Ductwork Insulation Cost

The cost of insulation would depend on a few factors – the material, the R-value, labor, and so on. Usually, duct insulation cost falls in the range between $0.95 and $2 per square foot installed.

Let’s have a closer look at what you are paying for:

  • The length of the ductwork

Of course, the longer the actual ductwork, the more expensive the insulation is going to be. The cost will also depend on the insulation ratings (R-3.5, for example, is cheaper than R-8.0).

  • The thickness of the ductwork

The thinner the ductwork, the more insulation material you would have to add to achieve the desired thickness. This is done in order to meet the recommended insulation levels.

  • Supplementary materials

Unfortunately, you can’t simply stick the material to the duct, you are going to need quite a few supplementary materials. Expect to pay $25-$50 for the supplies for every 1.000 square feet of insulation.

  • Labor costs

You can attempt doing the job yourself. It isn’t extremely challenging and won’t cost you a penny. However, if you are not used to working with such materials, you should expect to spend a wagon of time on the job.

When it comes to professionals, you will be asked to pay up to $0.80 per square foot for their services.

Tip: you can attempt completing the job on your own if it’s a small project. For larger tasks, experts recommend hiring professionals.

Even though the installation process might cost you a lot of money, in the end, it will definitely be worth it as high-quality duct insulation will help you save a small fortune on your electricity bills.

Ductwork Insulation Thickness

As a rule of thumb, the more extreme climate you live in, the more insulation you should add. People living in areas with freezing cold winters and boiling hot summers should consider going for the thickest insulation.

Moreover, it will make more sense to add a thicker layer, if you are planning on living in this particular house for decades. This will help you avoid a lot of insulation-related problems in the future.

You should plan on adding anywhere from an inch to 3 inches of insulation to your ductwork.

1-inch insulation gives you an R-value equivalent to 1.9.

1.5 inches – R 3.5

2.5 inches – R 6.0

3 inches – R 8.0

How to Insulate the Ductwork

There are a couple of steps to insulating ductwork. It is best to work with an HVAC professional who can make sure you are choosing the right insulation and installing it properly.

Determining the Right R-Value

Insulation is rated in terms of its thermal resistance. It gets an assigned R-value, which is a measure of the effectiveness of insulation.  Insulation with a higher R-value is a better insulator.

For your ductwork, you will want to choose an insulation with an R-value of least 5.

Sealing Before You Insulate

Before you insulate the ducts, you need to seal the ducts.

Ducts are inherently leaky at the joints where the pieces attach. It is almost impossible to build leak-proof ducts.

That said, once the ductwork is installed, you can seal the ductwork to reduce leaks. Don’t waste time insulating your ducts if you aren’t also going to be sealing the joints.

Use mastic to seal the ducts. Mastic doesn’t shrink as it ages, so it won’t pull away from the joints. It also doesn’t deteriorate over time. It will last the lifetime of your HVAC system.

Despite the name, don’t use duct tape to seal your ducts. It is sticky, ineffective, and breaks down over time.

Once you seal your ducts, you can insulate the ducts.

Choosing the Type of Duct Insulation

There is more than one way to insulate ductwork. The insulation type will be determined by your ductwork configuration and budget.

The two most common ways to insulate ductwork are

  • Wrapping the duct in a foil-faced blanket; or
  • Applying spray foam insulation to the outside of the duct.

If you need help deciding which type of insulation you need, set up an energy consultation.

Does crawl space insulation need to be replaced?

Damp or dangling insulation is a sure sign that your crawl space needs a revamp. If your home was built before 1990, it’s likely not up to today’s energy-conserving building codes. You may have very little to no crawl space insulation remaining

Your vented crawl space could be to blame for your high utility bills

Fiberglass insulation installed in the crawl space ceiling will not protect you from frozen pipes, cold floors and high heating bills. Ductwork in a vented crawl space is another problem. Outside air and temperatures make your ducts cold in the winter and hot during the summer. This forces your HVAC system to work overtime to deliver air at the proper temperature, cutting system efficiency by as much as 25-40 percent.

How we seal out the cold in your crawl space

Instead of worrying about your crawl space and making temporary repairs, let us permanently solve your cold weather problems. We don’t just winterize crawl space pipes or vents. Instead, we seal and winterize your entire crawl space foundation to bring your plumbing and heating system inside your home’s conditioned space. Here’s how our process works:

  • Air seal & insulate the rim joist. A tremendous amount of heat is lost through the rim joist that rests on your crawl space foundation. We prevent frigid air from leaking in by sealing gaps around the perimeter of your foundation. Then we reduce conductive heat loss by insulating the rim joist with foam insulation.
  • Insulate crawl space walls with rigid foam. We install high-performance ExTremeBloc™ rigid foam insulation against the crawl space walls. ExTremeBloc™ does what fiberglass can’t: it stops air leaks, never loses R-value, and can’t absorb or be damaged by moisture.
  • Seal & insulate the crawl space floor. In colder climates, we recommend installing foam insulation on the crawl space floor. This specialized flexible insulation is then covered with our strong poly moisture barrier that completes the sealing process. The crawl space is now isolated from outside conditions.

The Problem with Uninsulated Ductwork

The crawl space is an unconditioned space. This means that, like an attic or unfinished basement, you don’t heat and cool it.

If you have ductwork in your crawl space, the temperature of the duct will be the same as the temperature of the crawl space.

In the winter, a crawl space can be significantly colder than the living spaces of your home. The hot air leaves your furnace at the desired temperature. When it hits the ducts in the crawlspace, that hot air is cooled by the cold ducts. It comes out of the vents at a lower temperature than desired.

This means that your furnace has to work harder to warm up your home. It has to run longer and more frequently because you have losing heat at your crawl space’s ductwork.

On a hot summer day, the opposite would be true. The unconditioned spaces that house your ductwork will likely be hotter than the living spaces. You’ll cool the air in your A/C unit and then warm it back up by sending it through hot ducts.

Leaky ducts also create indoor air quality problems. Drawing crawl space air into the air supplied to the living space can introduce allergens and other air quality issues.

This set up is inefficient, in any weather conditions. It wastes energy and money. Thankfully, efficiency can be easily restored with proper insulation.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Caulk gun
  • Cordless drill
  • Dust mask
  • Knee pads
  • Lineman’s pliers
  • Safety glasses
  • Tape measure
  • Utility knife
You’ll also need a trouble light and leather gloves