Best Insulation for Basement

The basement can harbour mold and also allow drafts through the ceiling, rim joists, and the walls. Most homes especially the older ones lack insulation within the basement area making these spaces uncomfortable. Un-insulated basements can also cause the floors above to be extremely cold or even damp.

The insulation that you will choose for your basement will depend on the area of the basement you are going to insulate and what your specific needs are. We recommend installing both spray foam and mineral wool insulation. In this guide we’ll help you understand what insulation to use for different components of your basement and how to do it.

Let’s jump right into it!

Best Insulation for Basement Exterior Walls

Basement walls can either be finished or unfinished. Insulating the basement walls from the outside is considered the best method if you want to gain energy efficiency. Insulation on the exterior walls is also a great choice if you’re looking to have more space on the inside. Insulating the exterior walls of a basement also protects the foundation of the building from collapsing due to temperature variations.

However, it’s important to note that when insulating the basement exterior walls, you need to consider the drainage system. The method may therefore end up being more expensive because more measures have to be put in place. Besides, the method works best when installed during the initial construction of a home.

The best insulation for the finished walls on the outside of the basement is spray foam. Here is why spray foam makes the best insulation for this purpose.

Benefits of Spray Foam Insulation for finished Basement Walls

  1.   Prevents mold

Spray foam creates a moisture barrier preventing dampness in your space. Most basements are constructed using concrete. We all know how notorious concrete is for moisture retention. Such conditions favor the growth of mold. Consequently, mold is a health hazard and can also damage your home making the building weak and unstable.

Spray foam stands tall preventing any moisture from penetrating into the basement. Spray foam fills all cavities on the seams and edges of the walls making it perfect for moisture prevention.

  1.   Air sealing

Other than preventing moisture from infiltrating into the basement walls, spray foam also forms a great air seal. The insulation fills all gaps making sure that no air can pass through, a property that no other insulation can achieve.

  1. Strengthens a building

Spray foam upon curing forms a rigid layer that eventually becomes part of the walls. Due to the thickness and rigidity of spray foam, it strengthens the structure of your basement.

  1.  Reduces pollen and dust infiltration

Do you at times find your furniture full of dust a few hours after dusting? Well. The culprit may not be the windows or the doors but rather your basement walls. Spray foam forms a barrier preventing entry of dust or pollen keeping your home comfortable.

How to Install Spray Foam on Finished Walls of the Basement

The process of insulating the walls of a basement is quick and straightforward. However, there are several things you need to check before you start insulating the walls with spray foam.

  1.   Check the drainage

Never insulate walls that have water leakage problems because sealing with insulation can only worsen the problem. Check the drainage system first and fix any water leakage problems if any.

  1. Remove interior finishes

The next step involves eliminating any finishes on the walls such as plasters, any existing insulation, and dry walls.

  1.   Uninstall the doors and windows

For effective insulation, you can remove the doors and windows to give access to the openings around them that need insulation.

  1.   Flashing

Next, connect the house wrap or the building paper to the doors and windows rough openings. For this process, use a self-adhered and flexible flashing.

  1. Reinstall doors and windows

After flashing the rough openings and transitioning the air control, reinstall the doors and windows or replace with new ones.

  1.  Install insulation

Spray foam insulation can be applied directly onto the concrete walls of the basement. For this process, you need to have two hoses connected to each other at the nozzle, a gun, and the insulation. Spray foam as we all know comes in two cans as component A and component B. The chemicals only mix at the point the two hoses connect.

Wear protective gear because spray foam emits dangerous fumes if inhaled. Then, spray directly onto the concrete walls from bottom to top until all the walls are insulated.

  1.  Cover the walls

Most building codes require that after installation of spray foam on the walls of the basement, you install a gypsum cover over the insulation. Therefore, once the spray foam cures, the final step involves installing a drywall over it.

Now that we know how to insulate finished basement walls, let’s talk about the unfinished walls.

How to Insulate Unfinished Basement Walls

The best insulation for unfinished basement walls is mineral wool batts in combination with spray foam. Mineral wool batts are ideal for placing in between wall studs because they fit snugly offering thermal resistance. Besides, mineral wool has some water repelling properties that make it ideal for basement conditions.

It’s important to note that covering the warm side of the basement wall with spray foam can help prevent moisture infiltration. Therefore, combining spray foam with mineral wool insulation for your unfinished basement walls can help you achieve thermal resistance and consequently save you on energy costs.

How to Install Mineral Wool on Basement Walls

When fitting mineral wool, make sure to wear some protective clothing because the fibers can irritate your skin and eyes. Also, as you fit the batts in between wall studs, avoid squeezing too many batts on one cavity because it can lower its thermal resistance capabilities.

After you’ve installed the batts on all wall studs, it’s essential to place a cover such as a drywall or gypsum on top to give it a perfect finish.

Benefits of Mineral Wool Insulation

You’re probably why mineral wool stands tall as the best insulation for unfinished basement walls over other types of insulation. Here is why.

  1.  Lightweight

Mineral wool batts are so light that you can install them yourself within a short period. The batts also come in different sizes so that you can buy the size closest to your area of insulation. Besides, if you want to make adjustments, you can quickly cut the batts into your desired shapes and sizes.

  1.    Affordable

Compared to other types of insulation, mineral wool is affordable. Insulation such as spray foam is very expensive and if you’re using it alone, you may have to spend a fortune to have your space insulated.

  1.    Prevents moisture infiltration

Mineral wool insulation has good water repellency compared to insulation like fiberglass. Mineral wool therefore makes a great choice for basements where dampness is likely to be a problem.

  1.  Prevents dust and pollen

Are you worried that dust and pollen may affect the comfort of your home? Worry no more because with mineral wool, you can get rid of allergens that infiltrate into your house through basement walls.

Best insulation for Basement Ceiling

Mineral wool is the best type of insulation for basement ceilings. Mineral wool is made from molten glass, industrial waste, and stone. These materials are then spun into fiber like materials and used to create batts, rolls, and loose-fill insulation.

If you’re a smart homeowner, then insulating your basement ceilings is a noble move albeit lots of controversies over insulation of basement ceilings. Here is the main reason why you should use mineral wool for your basement ceilings.

Sound reduction

The reason why you’re going to want to install mineral wool into your basement ceiling is because it will help reduce sound. Different types of noises can come from the basement and are likely to distract your activities in the main house.

Before we go any further, let’s understand common causes of noise in the basement.

What are Common Causes of Noise in the Basement?

There are two main types of noises that can come from your basement. The first type of noise is impact noise. With this type of noise, you only hear it when sound hits a solid structure. For example, footsteps from someone walking in the basement, or if a ball hits the basement ceiling you may hear the impact from above the basement. Impact noise is mainly felt in the form of vibrations.

The other type of noise you may hear from the basement is airborne. This type of noise travels through the air. Such type of noise is like what’s produced by people talking in the basement, music, your HVAC, electricity, and water. Here is a list of some of the most probable causes of noise in your basement.

  • Blowers and pumps from the HVAC system
  • Water pipes running through the basement
  • The heating system especially the boiler
  • Music if you’ve converted the basement into a living area
  • People talking

Why do you want to install insulation that helps reduce noise in basement ceiling

As we improve our homes, it’s possible to repurpose the basement into an office, an extra bedroom, a playroom, or a music room. Without proper soundproofing, noises from above the basement ceiling can affect the occupants of the basement.

 For example if you’re working from your basement office and you can hear footsteps above, or the TV noises from the living rooms area affecting your work, then insulation isn’t an option anymore.

Best Insulation for Basement Floor

The basement floors are known for dampness and extreme cold especially if the home is older. If you use your basement as a storage, bedroom, or office, then you need to consider insulating the floors to make the room comfortable.

Other than comfort, by insulating the basement floors you also get to save on energy cost. As we all know insulation prevents heat gain and heat loss giving you energy efficiency. Now, let’s take a look at the best way to insulate your basement floors.

Rigid Insulation for Basement Floors

The type of insulation you use on the floors is dependent on the building codes regarding the height of the basement from the floor to the ceiling. Some insulation can add an extra layer of height than others.

Another aspect to consider is the type of floor because some floors in basements can be wet and others dry. You also have to determine whether the floor is uneven or leveled. Now, based on your evaluation, if you don’t have a problem with height in your basement, you have dry and level floors, we recommend using rigid insulation.

Types of Rigid Insulation

Rigid insulations are relatively thin but have lots of R-value which is an advantage to the homeowners. Here are 3 most common types of rigid foam insulation.

  •  Polyisocyanurate (ISO)

ISO has an R-value of R-5.7 to R-6 but some experts claim that the thermal resistance lowers as the temperatures go lower. This type of rigid insulation comes in liquid form and is then sprayed onto the surface which upon curing creates a rigid insulation. This is the most expensive type of rigid insulation.

Most ISO insulations come with an exterior vapor barrier which is usually a foil. The foil face prevents moisture infiltration. There are other ISO insulations faced with fiberglass but which aren’t moisture and air impermeable. Don’t go for rigid insulation with an interior face because it can worsen dampness problems.

  •     Extruded polystyrene (XPS)

The XPS rigid insulation is the intermediate to ISO. You’ll identify this type of insulation by its blue, green, and pink colors. This insulation has an R-value of 5 per inch. You can get XPS either faced or unfaced depending on what you’re looking for. The faced XPS has an extra layer of plastic which makes it moisture resistant and stronger.

If you’re concerned about the environment, then XPS isn’t the best choice because its blowing agent is known as a pollutant and can cause global warming.  

  •   Expanded polystyrene (EPS)

EPS is the most widely used form of insulation for basement floors. It has the lowest R-value of about 4 per inch. EPS can be used in direct contact to the ground and you can also apply treatment to keep insects away. If you compare this rigid insulation with the other two, it’s the least expensive. Thus, if you’re looking to insulate your basement floors without breaking your bank, then this is your best choice.


The basement is notoriously known for being cold and damp. Most basements are found below the ground and can therefore get damp from infiltrating wetness from the soil around. Insulating the basement floors, walls, and ceiling is therefore a no brainer if you want to save energy costs and enjoy a comfortable home. This guide gives you an idea of what insulation is best for different components of your basement and how to insulate.