Is It Necessary To Insulate Basement Walls? (Lower Your Energy Bills)

Homeowners are reluctant to spend money on insulating basements that they use only as storage spaces. However, basements are often damp and cold because their walls are not well insulated. Do homeowners really save money by not insulating their basement walls?

It is necessary to insulate basement walls to conserve energy and better regulate the temperature in a building. It will also make the basement comfortable enough to be used as additional living space. However, basement wall insulation is not recommended in areas prone to seasonal flooding.

Is It Necessary To Insulate Basement Walls?

In the rest of this article, I’ll examine this topic in more detail, including the benefits of basement wall insulation. I’ll also explain how insulation works and list the materials commonly used to insulate basement walls.

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Understanding Insulation

To understand why basement wall insulation is necessary, we must first understand how insulation works.

In simple terms, insulation restricts heat from flowing out of or into the insulated space. T

hat brings us to the question: how does heat flow?

Heat Flows in 3 Ways

Heat flows from a warmer place to a colder place until the temperature difference no longer exists.

Heat flows in three ways:

  • Conduction
  • Convection
  • Radiation

Insulation works by putting up barriers to restrict heat flow by conduction and convection.

The barriers are made of materials that are poor conductors of heat, and most have air pockets that disrupt conductive heat flow.

Reflective insulation materials are used for radiant heat.

Why It’s Necessary To Insulate Basement Walls?

A simple basement with concrete walls and no insulation
A simple basement with concrete walls and no insulation

In winter, heat from the heated areas in your home flows into unheated areas like the basement and to the cold outdoors. If the basement is not insulated, much of the heat will escape into the cold earth around it, although the earth is not a very good conductor of heat.

Your HVAC (heating, ventilation, and air conditioning) system has to work harder to replace the heat loss to keep the heated areas at a comfortable temperature.

In summer, the reverse happens. Warm air from the outdoors flows into your cooled living spaces, some of it entering via the uninsulated basement walls.

Again, the load on your HVAC system will be high, this time to remove the heat gained.

Studies show that about 20% of the heat loss from a home occurs through the basement.

So the basement must not be left uninsulated if you want to make your home energy efficient.

Some people think it’s sufficient to insulate the ceiling of their basement and prevent heat loss from the above-grade floors of their house.

However, insulating the basement walls offers better thermal performance than ceiling insulation in most cases, according to Energy Star, a program run by the U.S. Environmental Protection Agency (EPA) and the Department of Energy.

Insulating the basement walls will bring the basement within the house’s thermal cover, making it part of the conditioned space.

With all walls from the basement to the roof insulated, the overall heat loss will be reduced.

However, basement wall insulation is not recommended in areas prone to seasonal flooding because water logging can damage the insulation.

Insulating the basement ceiling will be the better option in such places.

Benefits of Insulating Basement Walls

Additional Living Space in An Insulated Basement
Additional Living Space in An Insulated Basement

Basement wall insulation involves significant upfront costs for homeowners, especially if they engage professional contractors to do the job.

The investment will, however, yield considerable benefits over the long term.

The benefits include:

1. Savings on Energy Costs

As mentioned earlier, proper insulation will reduce your HVAC system’s load during heating and cooling seasons.

That will translate into savings on your utility bills.

Moreover, your HVAC system will work efficiently, saving you money in maintenance costs.

According to a North Dakota State University publication, basement wall insulation can save homeowners up to 20% of their annual heating bill.

Over the long run, you’ll save more than the money you spend upfront on insulating your basement walls.

2. Additional Living Space for the Family

Insulating your basement wall will make the space more comfortable. You can consider several practical uses for the space.

You could, for instance, turn it into a home theater, a gym, or a play area for children and adults alike.

A well-insulated and comfortable basement will also increase the value of your home.

3. Healthier and More Hygienic Environment

Basement wall insulation is not just about saving money and more comfort; it’s also about protecting your health.

Using the appropriate Insulation material can help address existing issues in your basement that could negatively impact your health.

4. High Moisture Levels Promoting Mold Growth

Basements are prone to water seepage, making the walls damp.

Dampness promotes the growth of mold, which can lead to allergic reactions, flu-like symptoms, skin rashes, and lung infections.

If there’s water seepage, it’s best to address the issue before installing the insulation.

5. Prevent Radon Entry Through Cracks in Basement Walls

Radon is a radioactive gas that emanates from granite, rock, and soil.

Carried by water and air, radon enters buildings through cracks and holes in underground structures.

Radon is the second leading cause of lung cancer in the U.S., accounting for about 21,000 deaths yearly.

You can check the radon levels in your basement with a radon test kit.

I recommend the RadonScreen Home Radon Test Kit from It comes with a return envelope to mail the device to RadonScreen’s lab for an EPA-approved test. The fee for the test is included in the price of the kit.

6. Prevent Pests Infestations

Basement wall insulation can also prevent termites, ants, and other pests from making their homes in the wall’s holes, cracks, and cavities.

Irrespective of the insulation material, you should fill and seal all the holes, cracks, and cavities before insulating the wall.

Sealing them will help block pests and radon from entering through the walls.

Where To Insulate: Inside or Outside?

A basement insulated on interior with rockwool
A basement insulated on interior with rockwool

You can go about insulating your basement wall in two ways: from the inside or the outside.

For existing houses, interior insulation is usually preferred because it costs significantly less than exterior insulation, which involves excavating the ground around the basement.

Interior insulation is also easier to complete as a DIY project, but it will reduce the basement floor area (by the width of the insulating material).

During the house construction a basement is insulated on exterior with rigid foam board
During the house construction a basement is insulated on exterior with rigid foam board

Exterior insulation is more effective in minimizing heat loss, especially through spaces between the walls and the foundation, and preventing moisture from permeating the walls.

However, it is only practical for new constructions.

Insulation Materials for Basement Walls

When selecting the insulation material for your basement walls, you need to consider its R-value, which measures how resistant it is to heat flow.

The R-value you need depends on where you live, and the higher the R-value, the better the insulation.

Here are some of the better options for basement wall insulation:

1. Rigid Foam Board

Rigid foam board (polystyrene) for basement insulation
Rigid foam board (polystyrene) for basement insulation

Rigid foam boards are made from expanded polystyrene foam and come in different sizes and R-values.

They are ideal for flat concrete walls and unframed walls.

Rigid foam boards are ideal for DIYers because they are easy to install; The boards are scored, so you can cut them to the required sizes by snapping off sections. You can also use a wood saw to cut the boards.

You can fix the board to the wall with screws or strong adhesives.

Then seal off the perimeter using a foam sealant such as the Loctite White Insulating Foam Sealant, which you can order from

You can also use the sealant to fill and seal holes and cracks in the wall before installing the foam boards.

It’s good for cracks up to 3 inches (7.6 cm) wide.

3. Spray Foam

A basement ceiling insulated with spray foam
A basement ceiling insulated with spray foam

Spray foam is polyurethane foam, and it’s applied to the wall using a spray gun.

The foam expands to fill up all the holes and cracks in the wall, keeping radon and pests away from your basement.

Spray foam is considered one of the best options for basement insulation because it works well even in damp or moist environments.

However, it’s also more expensive to install than rigid foam boards.

The higher cost is partly because spray foam application requires expertise, and professionals are often hired to do the job.

Polyurethane contains toxic compounds.

Workers spraying it must don safety gear to protect their eyes, nose, and skin.

When the foam has set on the surface, it ceases to be a health hazard.

4. Mineral Wool

A basement ceiling insulated with mineral wool
A basement ceiling insulated with mineral wool

Mineral wool is a fibrous material made from molten rock and slag, a blast furnace byproduct from iron and steel plants.

Apart from being a good insulator, it’s resistant to water and fire and is soundproof.

Also known as rock wool, mineral wool is more expensive than many other insulation materials on the market.

Mineral wool comes in the form of large thick mats and can be installed the same way as rigid foam boards.

If you’re planning to use mineral wool to insulate your basement wall, I recommend ProRox SL 960 Rockwool from It’s made from rock and will last a lifetime.

Final Thoughts

Unless you live in a flood-prone area, you’ve got much to gain by insulating your basement walls.

Before you get down to insulating your basement walls, you need to consider whether you’re insulating the exterior or interior and what insulation material to use.

Cheers, tools owners!

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Hi there! My name is Jack and I write for ToolsOwner. I have a passion for everything related to tools and DIY projects around the house. You often find me in my workshop working on new projects.