The Best Insulation for Bathroom Walls Interior and Exterior Parts

Bathroom insulation is an excellent way to prevent the growth of rot, mold, and mildew while soundproofing the space. Choosing the proper insulation for bathroom walls depends on several factors, including budget, preferences, and moisture control.

Find out some of the most recommended types of insulation for the bathroom’s exterior and interior walls below.

Best Insulation for Bathroom Exterior Wall

Insulation of the exterior wall of the bathroom, especially when using energy-efficient materials like rigid foam or fiberglass, and accompanied by a vapor barrier, is generally seen as a more effective way to prevent moisture-related problems.

This approach ensures that mildew growth is minimized and enhances the bathroom’s overall comfort and energy efficiency. This approach ensures that mildew growth is minimized and the wall cavity is protected.

Read also: The Best Insulation for Bathroom Walls

Some of the most common types of insulation used for bathroom wall insulation are meant to be performed on the exterior parts of this building section, including fiberglass, cellulose, and foam insulation.

Here are brief details about each insulation type that you may choose for the exterior walls of your bathroom:

  • Fiberglass insulation: Fiberglass is the cheapest option compared to other recommended insulation types for the exterior walls of your bathroom. This particular type of insulation can be acquired in batts or blown-in installations. That being said, it’s important to note that fiberglass is the least effective insulation material among the other insulation types in this list due to the lack of thickness.
  • Cellulose insulation: Cellulose is a subtype of blown-in insulation. It makes the most eco-friendly insulation in the market nowadays because it is made from recycled stuff. This insulation material is resistant to insects, fire, and mold because it receives chemical treatment.
  • Foam insulation: Rigid foam insulation is a fairly new method of insulation that you can try for your bathroom walls. It has an extremely soft and smooth texture, but it builds a solid air seal and closed cell barrier that’s very hard to penetrate by air and moisture after it dries.
  • Rockwool: This insulation is also called slag or mineral wool. It is also an environmentally friendly insulation material made from molten substances to fibers. However, it falls into the pricier side of the range.

Best Insulation for Interior Bathroom Walls

The question of whether you insulate bathroom walls is not rare, but even more so for people who wonder about the importance of insulating the room’s interior part.

best insulation for bathroom walls

In general, most professional constructors would say it’s not required to insulate the interior walls of the bathroom. Still, if you plan to do so, you may as well, particularly to reduce energy costs.

Proper insulation in these areas can help maintain a consistent temperature, contributing to an energy-efficient home. A lot of modern houses also adopt this method for noise reduction purposes.

Insulating the interior walls of your bathroom also offers another benefit of comfortable shower wall surface temperature when you lean against it because it prevents the heat produced by hot shower to escape so quickly.

Interior wall bathroom insulation is tricky; professionals mostly perform it because it’s typically done before the shower and bathtub are installed. Due to this, it’s more recommended to insulate the parts during a major remodeling or the initial build rather than doing it as a solo project.

Read also: What is Cellulose Insulation Made of?

Material choice also becomes more challenging when it comes to interior bathroom walls. Fiberglass is widely used, but it can be prone to moisture penetration. Spray foam is recommended if you use it around the shower walls to protect the plumbing and pipes.

It should be noted that regardless of what insulation material you choose for the interior walls of the bathroom, the quality should match the one installed for the exterior walls. This is meant to reduce the chance of frozen spots on pipes or whisking away moisture accumulation.

When installing insulation in your bathroom, it’s crucial to consider the space’s specific needs. Bathrooms are prone to high humidity, so selecting materials that resist moisture and prevent the growth of mold and mildew is essential. Paper-faced insulation products can be a good choice, as they offer additional protection against moisture.

There is a list of options other than the best insulation for bathroom walls mentioned above that you can find in the market. It includes glass mat gypsum fibre-cement and more that you can research further.

Enhancing Energy Efficiency and Cost-Effectiveness with Bathroom Insulation

When considering the best insulation for bathroom walls, it’s important to consider the potential to reduce energy consumption. Well-insulated walls can help maintain a comfortable temperature in the bathroom, reducing the need for excessive heating or cooling.

This is particularly relevant when installing spray foam insulation, as it provides an airtight seal that significantly lowers energy bills. Additionally, understanding the cost of spray foam insulation compared to other types like fiberglass is crucial for budgeting your bathroom renovation project.


In conclusion, selecting the right insulation for bathroom walls, both interior and exterior, is crucial for moisture control, soundproofing, and energy efficiency. Whether you choose spray foam insulation or another type, the goal is to create a comfortable, energy-efficient space in your bathroom.

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Insulator is a skilled author and Insulation expert with years of experience in the field. He has authored several articles and books on various aspects of insulation installation, maintenance, and repair.