Do HVAC Return Ducts Need To Be Insulated

Guide to cleaning a duct properly and regularly
  • Author: Amanda Arnold
  • Posted On: October 24, 2022
  • Updated On: August 21, 2023

You will need to insulate your ducts if exposed to environments with unfavorable air temperatures. By doing this, you’ll be able to reduce the temperature difference between the inside and exterior of your home.

If you don’t insulate them, the air’s temperature differential inside and outside will result in heat loss or gain. The more dramatic the temperature differential over time, the more energy is required to maintain a comfortable indoor climate.

Insulation is required if return air ducts pass through areas where the return air temperature is affected. Typically, exhaust air ducts are not insulated. Insulation keeps moisture from condensing and leaking out of ducts.

Ductwork refers to the system of pipes that your domestic forced-air HVAC system uses to transport warm or cooled air. To get more vital details regarding your air ducts, continue reading.

Do you Also Need To Insulate Your Cooling Duct System?

There are several justifications for insulating a cold air return. The first is that insulation can prevent cold air from leaking into the living area and keep it in the basement or crawlspace where it belongs.

Second, insulation can lessen air conditioner or furnace noise. The return ducts can also be kept from freezing in cold weather with insulation. Use insulation that has been approved for use in contact with ducts if you’re thinking of insulating your cold air return.

Remember that if the return ducts in your furnace room freeze, you will lose efficiency if your home is primarily heated by natural gas or propane. So, it makes sense to insulate them to prevent issues with frozen ducts throughout the winter.

Do You Really Need To Insulate Duct Work?

In addition to the supply ducts that carry the conditioned air, your HVAC system also has a system of return air ducts that transport the exhausted air back to it. The many advantages of insulation are lost, however, if they are not adequately sealed or insulated.

HVAC ducts pass through several rooms with various temperatures before delivering air through the registers. It suggests that the system must raise the duct’s temperature above a certain threshold to distribute the desired air temperature throughout the structure.

Before the building can be heated, the furnace in the basement must force air through chilly ducts. The opposite happens when you use the air conditioner on a hot day. Warm ducts must be overcome before the building can be successfully cooled.

The eventual occurrence of heat transfer is a usual difficulty to overcome during the initial operation. In contrast, your system often cycles to give thermal insulation while preserving heat in the interim. The joints of ductwork also leak.

Any air loss implies it will take the system longer to provide the surroundings with enough hot or cold air. Insulation aids in plugging these holes, boosting airflow, and enhancing the system’s overall effectiveness.

Types Of Insulation For HVAC

Only a few forms of insulation are utilized for HVAC ducts. Due to ducts being built above the ceiling, it is frequently impossible to view the insulation. Insulation is typically applied outside of ducts to stop energy loss and condensation.

Nevertheless, it is occasionally utilized inside ducts to lessen noise, especially in air-handling unit ducts.

  • Polyethylene Insulation

Ducts for exhaust ventilation and air conditioning are insulated with polyethylene. Polyethylene insulation is recommended when the duct is exposed. Concealed ducts use Polyethylene foam as insulation because it is a more expensive material.

Ducts insulated with polyethylene rather than fiberglass are more desirable because they don’t wrinkle and are safer to work with.

  • Fiberglass Insulation

Ductwork is wrapped in pliable fiberglass air duct insulation. Foil serves as a support for the visible outer backing. Insulating and preserving the fiberglass are also functions of the foil. Technicians secure the air duct insulation by wrapping some heavy-duty tape around it.

Rigid board insulation is effective for rectangular ducts. Insulation of stiff board is fastened to the duct with clamps or clasps. One of the best insulating materials on the market is fiberglass. To get your ductwork inspected, you can hire professionals.

They aid in determining whether fiberglass duct insulation is suitable for your structure.

  • Rockwool Insulation

The inside surfaces of large air conditioning ducts are frequently soundproofed with Rockwool, a typical sound-insulating material. When replacing Rockwool, experts occasionally use fiberglass that precisely matches the requirements.

However, Rockwool is recommended because it resists tearing in ducts where the wind is blowing at a high pace.

Use Thick Insulation For Extreme Climate

Generally speaking, the more insulation you should apply, the harsher the climate you live in. Residents of places should choose the thickest insulation with bitterly cold winters and scorching summers.

Adding a thicker layer will make more sense if you intend to stay in this particular house for a long time. This will assist you in preventing numerous potential issues with insulation. Anywhere your ducting is exposed should have insulation added.


You now know all there is to know about ductwork insulation. In a word, place insulation in your ducts if you can because there will be many advantages. If a little amount of insulation needs to be installed in your home, you might be able to do it yourself. The general rules would be quite similar regardless of the area you have chosen to work on.

There must be insulation on all supply ducts. Return air ducts that do not pass through conditioned space are subject to it. To prevent your electricity bill from going up, take care of your return duct insulation issues as soon as you discover them.

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Author: Amanda Arnold

Amanda has been working with ConstructionHow since 2021. Her experience spans over 5 years in the creative niche such as home decor and trends, landscaping, renovations, and custom architectural values. As a home designer expert, she has a keen eye for the latest home improvement trends with accurate facts that readers find impossible to ignore. Being invested in home-building trends is how she has gained her lucrative expertise exploring more to bring a positive ambiance for all homeowners (and even tenants!). Currently, she lives in a beautiful beach home, a source of fascination for her.