Most homeowners believe that insulating the roof, walls, and ceiling are enough to resist heat flow and provide a stable and comfortable temperature inside the house. While that is partly true, adding insulation in floors—specifically in houses with multiple floor levels—provides additional thermal, acoustic, and moisture-proofing benefits. 

Floor insulation improves the temperature level on each floor by blocking heat, as well as updrafts of air, from the space below and vice versa. It helps to reduce sound transfer and block unnecessary noises. It serves as a moisture barrier and prevents the pipework system from freezing. Most importantly, the installation cost is affordable.

Still in doubt? Keep reading to learn more about the perks of adding insulation between floors. 

The Importance of Insulation Between Floors

Insulation is an important element in residential and commercial structures. Consequently, it makes insulation between floors as important as other types of insulation systems.

Here’s why.

Insulation generally serves as a mechanism to resist heat flow and heat gain. And by regulating the flow of heat and providing a stabilized temperature within the house or building, insulation reduces cooling and heating costs as well as provides comfort. 

The purpose of adding insulation between and within floors works virtually the same. It prevents air movement, as well as heat flow, between two rooms that are divided by floors. And updrafts of air and heat coming from the room below will not penetrate the room above. This way, if a sudden temperature change transpired in the room below, the temperature in the room above will not be affected.

Moreover, the US Department of Energy also recommends insulating floors as a standard, stating that floors above unconditioned spaces like unheated garages and crawl spaces should be insulated.

Certain floor and room conditions also require insulation, such as:

  • Slab floors that are built directly on the ground
  • In houses with unfinished attic space, insulation over and between floor joists will help seal off the space below
  • Any part of the floor that is cantilevered beyond the exterior wall below
  • Extend insulation into joist space to lower airflow
  • Insulation works as an acoustic barrier too and would be great to add if you want to reduce sound and noise transfer between floors 

The Pros of Insulating Between Floors

Floor insulation is not common in residential and commercial structures. But just like other installation systems, adding insulation between floors of your house or building provides several benefits.

1. Stabilized Temperature

Adding insulation between floors provides significant thermal benefits, specifically a stabilized temperature within rooms on each floor. Heat naturally travels to spaces with lower heat energy more so than to those with high heat energy. As a result, it is difficult to keep a house cool during summer and warm during winter.

This is where you will need insulation systems.

As discussed, insulation resists heat flow and, therefore, prevents heat loss and gain. And adding insulation between floors can significantly lower heat loss and gain between different levels of your house. If, for instance, the master bedroom is above the kitchen area, the heat produced from cooking and grilling will likely penetrate the room above. But if the floor between these two areas is insulated, the heat will find it difficult to move and escape to the room above.

The same goes for floors above unconditioned spaces like crawlspaces and unheated garages.

2. Reduced Sound and Noise Transfer

Sound, just like heat, naturally moves from one place to another without intervention. And in two- or three-story houses, sounds such as music, loud voices, footsteps, and even appliances can travel between floors and create unnecessary noises.

Adding insulation between floors can prevent sound transfer.

Insulation between floors provides acoustic benefits—soundproofing, specifically. Batts and rolls insulation are commonly the materials used if the objective is to reduce sound and noise transfer.

Specialized acoustic insulation is also available if you want a more effective material. The batts are denser and thicker compared to traditional thermal insulation batts and can help contain sound and create quieter spaces. It naturally offers thermal insulation as well.

3. Additional Vapor Barrier and Reduced Floor Moisture

Moisture, just like heat, cannot pass through insulated assemblies. Insulation serves as a barrier that blocks moisture produced specifically by cold temperatures. Insulation as a vapor barrier is particularly efficient as well if you use spray foam.  Hence, floors with insulation produce less to no moisture too.

However, this will only work if there is no water leakage within the assembly. The room will also require a heating device such as a dehumidifier or a furnace to support the insulation and effectively keep the floor dry at all times.

4. Prevent Pipes From Freezing

Floor insulation is also a great solution for avoiding frozen pipes. It essentially serves as a barrier and restricts air movement within the assembly. It also functions as extra protection to further stabilize the floor temperature and is specifically beneficial if the pipes are installed under the floor.

Frozen and broken pipes are common in residential and commercial spaces located in areas with icy weather and where the temperature reaches the below-freezing point. And such a situation is troublesome, specifically during the winter season.

It is the cheaper and more convenient alternative, as well, compared to when you insulate exterior walls and seal off crawl spaces.

5. Saves Space

Floor insulation can help you save space at the same time. Wall, ceiling, and basement are the most common areas that get insulated. And these often occupy a large amount of space. Wall and basement insulation, for example, are usually four to six inches thick.

6. Floor Insulation Is Cost-efficient

Compared to the typical insulation system homeowners know, floor insulation is a much cheaper option. It is especially true if you are planning to insulate your entire house, as it typically requires using several types of insulation to achieve the best results. 

The Disadvantages of Insulating Between Floors

While floor insulation is highly recommended by the US Department of Energy, the system may also pose risks and disadvantages.

1. Hazardous When Wet

While insulation can withstand moisture produced by cold temperatures, constant exposure to water can damage and break the insulation. And wet floor insulation is dangerous.

That’s because:

  • Wet insulation will eventually break
  • Wet insulation is heavy and could prompt the floor to collapse
  • Wet insulation is a perfect breeding ground for mold and mildew

Wet floor insulation happens only when there is water leakage within the assembly. As such, make sure that your water system is in good condition. Water pipes connecting across rooms must be properly and tightly sealed to avoid leakage.

Removal of insulation may be required too—particularly if the material is already wet—to avoid electrical shock. 

2. Prone to Mold and Mildew

Mold and mildew pose health risks with regular exposure. If inhaled, it could cause allergic reactions and respiratory problems, including runny nose, sneezing, itching, coughing, as well as difficulty breathing.

Certain types of molds can also lead to a severe respiratory problem called “aspergillosis.” And the symptoms may vary from breathing problems, coughing, headache, and weight loss.

Moreover, mold on insulation could also create an updraft of air with an unpleasant smell.

3. Installation Process Is Laborious and Time-consuming

Floor insulation is often installed during house construction since the process is much easier than when the foundation and the floors are already completed.

As such, if you are planning to add floor insulation, expect a strenuous and time-consuming process. You will have to hire a professional insulation installer to assess and help you. To be effective, floor insulation requires proper installation.

What Insulation Is Best Used Between Floors?

Fiberglass, spray foam, and rockwool are the best materials to insulate floors. Here’s why.

Fiberglass Batts and Rolls

Fiberglass batts and rolls are popular insulation materials used in residential as well as commercial structures. It is easy to install, budget-friendly, and naturally fire-resistant. Hence, it is commonly used to insulate attics, walls, crawl spaces, and the basement.

Fiberglass blanket insulation, on the flip side, is also an excellent material to use on floors. It is particularly suitable to use between joists on suspended floors. It is, however, not recommended in solid flooring as it could make the floor covering lie unevenly.  


  • Affordable
  • Easy to install
  • Suitable for suspended floorings
  • Made from fire-retardant materials


  • Not suitable for solid floorings
  • Prone to mold and mildew

Spray Foam

Spray foam is a liquid foam that, when sprayed, expands, and fills the space up immediately. It is popularly known for its ability to fend off air movement within the assembly, making it moisture-resistant. 

Spray foam is typically used in awkward and hard-to-reach areas. In flooring, it is best to use it in between the joists of suspended wood flooring. The only catch is that it is quite expensive. 


  • Can insulate hard-to-reach areas
  • Quick to install
  • Serves as thermal and air barrier


  • Costly
  • The installation requires some experience

Rockwool Slabs

Popularly known as Rockwool, mineral wool is made from recycled slag, volcanic rock, dolomite, and basalt. Aside from traditional insulation, it is also suitable to use as floor insulation. It is easy to cut into pieces as well as to install. In fact, many installers use this in uneven spaces ad even warped joists. It is best to use suspended timber flooring.


  • Provides excellent thermal benefits
  • It is a non-combustible material
  • Easy to cut and install
  • Can be used in hard-to-cover areas
  • Requires support to keep it sturdy
  • Installation process is time-consuming

Should You Insulate Floor Joists?

The US Department of Energy recommends the insulation of floor joists.  Per the organization, floors be insulated in between and over joists to seal off unconditioned spaces below such as the basement or garage. Insulation must be extended into floor joists too, to help minimize airflow.

Insulation between floor joists also provides several advantages, including thermal, vapor, and energy-saving benefits. But to be specific, adding insulation between floor joists helps prevent excessive moisture and drafts from penetrating through floors due to cracks and gaps. It is also beneficial in houses with uninsulated basements.

Should You Insulate Attic Floor or Ceiling?

The decision whether you should insulate the attic’s floor, or the ceiling depends on a variety of factors. If the attic is simply a utility space, insulating the attic floor will be the most practical choice. Attic floor insulation is a standard if the room below or above is unfinished and uninsulated, as explained earlier.

On the other hand, if you are planning to turn the attic into a livable space, such as a guest room, then adding insulation within the ceiling is the most practical choice. Adding floor insulation is not required in such a scenario, but it would provide further comfort.


Justin's been in construction for over 20 years in both new build and renovation. With experience in both commercial and residential construction, he specializes in healthier and more energy-efficient homes.

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