Photo of a comfortable modern living room decorated in white. Interior wall insulation contributes to indoor comfort.

Insulation is a crucial factor in an energy-efficient home. So if you are hoping to save on energy costs or, even better, are striving to have a net-zero home, it’s worth taking some time to think about insulation.

We all know we need to insulate exterior walls and attics. But while insulating interior walls isn’t necessary in most cases, it can help with soundproofing, energy efficiency and heat transfer between rooms, and moisture control. Be sure to check local building codes to be sure!

To explore the details of each benefit, we’ve expanded on them below. We’ve even found some natural insulation options for your eco-friendly green home!

Should You Insulate Interior Walls?

You may feel like you already have enough insulation in your home. Or you may be wondering why you should insulate your interior walls if it isn’t required.

There are several benefits gained by adding interior wall insulation. Let’s examine them.

Interior Wall Insulation For Soundproofing

One advantage of interior insulation is its sound-dampening capabilities.

Since most building codes don’t require interior insulation, the only difference between the TV’s noise in the next room and your peace and quiet is a little wood or drywall.

Photo of a woman with a frustrated expression holding gray throw pillows over both ears.
Interior wall insulation might just save your sanity.

Even if you don’t have a home theatre system, you will notice the difference when you install new insulation.

With interior wall insulation, you can listen to your music in one room while the kids (or your roommate) listen to music in another without sounding like a battle of the bands.

I mean, who couldn’t do with a little more peace and quiet in their home?

Insulating Interior Walls For Energy Efficiency

While having a quiet home is nice, one of the main benefits of interior wall insulation is increased energy efficiency.

Like insulation for your exterior walls, attics, and basements, interior insulation can help lower your home’s heating and cooling costs. A well-insulated home is key if you are looking to lower your carbon footprint.

Insulation is especially important around rooms you don’t regularly use, like storage areas or guest rooms.

Insulate Interior Walls For Moisture Control

A worker wearing a face mask and safety glasses handling a mineral wool insulation batt being used to insulate interior walls.
Mineral wool is heavier than fiberglass insulation and has slightly better insulation properties.

As much as we try and control it, moisture collects in our homes. It’s in our bathrooms from showers and in our kitchens when we cook.

If you choose an insulation option with a vapor barrier, you can help control this moisture. That will help prevent unhealthy mold and mildew growth in your walls. 

What R-Value Insulation for Interior Walls?

The building codes for your area set out the requirements for R-values for insulation.

When talking about building codes, it is important to remember that these are the absolute minimum requirements when you build your home.

Codes are there to make sure your house won’t fall down or catch fire. I don’t know about you, but I always strive to be above the minimum.

And it’s the same when building or buying a home. You don’t want just the minimum requirements. You want to exceed the minimum requirements.

Of course, building codes and common building practices vary by region, as do insulation requirements. When looking at insulation codes, you will start to see talk of R-values.

So, before we get into the nitty-gritty of codes, let’s talk about R-value.

R-Value Meaning

R-value is an important number to know when talking about insulation. The R-value tells you how well a material impedes the flow of heat.

Scientists measure each material in a lab and assign it an R-value based on how much heat is stopped by one inch of insulating material. The higher the R-value, the better the material is at blocking heat.

As I said, R-values are based on one inch of material. So, if you are using more than one inch of material, simply multiply the R-value by the number of inches you use to get your actual R-value.

What Is a Good R-value? – Code Requirements

Your home’s insulation requirements will change depending on where you live in the country. Depending on what part of your home you are insulating, different R-values are needed.

While building codes vary from state to state, you can find the minimum R-values recommended for your region on the EnergyStar website. In addition, they provide numbers for attics, floors, and exterior walls.

You’ll notice that the interior walls are missing. That’s because, in many cases, adding interior wall insulation is not standard building practice.

However, interior wall insulation is important if you want an energy-efficient home. You can use the same R-value recommended for your region’s exterior walls.

While interior wall insulation is easiest to install in new construction, it is possible to insulate existing interior walls.

Types Of Interior Wall Insulation

There are many types of installation to consider when deciding to insulate your interior walls. So let’s take a look at some of the common and not-so-common types of insulation.

Photo collage showing different types of insulation that could be used for interior wall insulation.
There are lots of options when it comes to insulation! Check out our Ultimate Guide here.

Fiberglass Insulation

Fiberglass is what we commonly think of as insulation—rolls of pink fibers that look like cotton candy. Fiberglass is made by the heating glass until it is molten and then spinning it into fibers.

Much of the glass used to make fiberglass comes from recycled glass bottles, meaning it is a more eco-friendly option than you might have thought.

A lightweight material, fiberglass is easy to install. You can purchase batts or rolls or decide to have this type of insulation blown into your walls.

Because fiberglass is affordable, it is a popular insulation choice. However, some people are concerned about the formaldehyde used in processing it and its long-term health risks in the home.

Mineral Wool Insulation

Don’t confuse mineral wool with sheep’s wool, which we will discuss briefly.

Mineral wool is made from industrial slag or basalt. Like fiberglass, the materials are heated until they are molten and spun into fibers.

Its R-value is similar to fiberglass, as is the installation process. You can buy mineral wool in batts or rolls.

Cellulose Insulation

A pair of cupped hands holding cellulose of the type that is often used to insulate interior walls.
Cellulose is an eco-friendly material that can be used to insulate interior walls.

Cellulose insulation is probably the oldest insulator, made from plant-based fibers. Nowadays, when we talk about cellulose insulation, we’re referring to a type of insulation usually made up of recycled newsprint.

The paper is ground down, the dust is filtered out, and a fire retardant is added. The remaining fibers can be blown in as loose fill or dense packed. Dense packing is preferred, as loose fill can settle, leaving gaps in your insulation.

Cellulose insulation is a very affordable insulation choice.

Polystyrene Insulation

Polystyrene, which you probably think of as styrofoam, is one of the better insulators. Its higher R-value means you can install less insulation. In addition, it comes in rigid boards, which makes it easy to install.

While polystyrene doesn’t seem very eco-friendly at first glance, the energy savings you get with it can help you reduce your carbon footprint.

Sheep’s Wool Insulation

Sheep's wool closeup. The wool has been sheared from the sheep and is light brown and white in color. The wool can be used to insulate interior walls.
Sheep’s wool isn’t just suitable for knitting into sweaters. It is a highly effective heat insulator, suitable for use in insulating internal or external walls.

If you are looking for a more natural option, sheep’s wool insulation is becoming increasingly popular. The R-value is similar to what you get using fiberglass, but you don’t have to worry about possible chemical interactions affecting your health.

Like fiberglass, you can purchase rolls or batts and install them between your studs.

Just like a wool sweater keeps you warm even when wet, sheep’s wool insulation performs well in damp environments. After all, sheep have to stay warm in the rain, too. Not only that, but it also works as a very effective sound dampener.

The only downside to sheep’s wool is that it is a bit more expensive than your traditional insulation choices.

Is Internal Wall Insulation Worth It? – Final Thoughts

There are many reasons to insulate your interior walls. While the minimum standards where you live may not require interior insulation, no one wants to live in a house that just meets the bare minimum.

By installing insulation, you can create a more comfortable, energy-efficient home.

While you probably don’t notice how much sound carries in your home (or maybe you do), I’m certain you will appreciate the peace and quiet insulation can provide. But quiet is just a bonus.

The true payoff will come when you look at your utility bills and see how much money you are saving.

With a variety of insulation options out there for every budget, you can decide how much you are willing to invest. Regardless of your choice, your insulation will pay for itself with your monthly savings over time.

So, you can’t go wrong whether you are thinking about interior wall insulation for comfort or efficiency. 

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