As a building and construction expert with years of experience in the field, I've had the opportunity to work on a variety of projects, including the installation and maintenance of insulation in residential and commercial settings. When it comes to the type of insulation to use behind shower walls, there are several factors to consider, including moisture resistance, durability, and ease of installation.

Moisture Resistance: Shower areas are prone to high humidity and water exposure. Therefore, the insulation material should be able to withstand moisture without degrading. Water-resistant or waterproof insulation materials are preferred for this area.

Durability: The insulation should be durable enough to last for a long time without the need for frequent replacements. This is especially important in areas that are difficult to access for maintenance.

Ease of Installation: The insulation should be easy to install, requiring minimal disruption to the existing structure and causing as little inconvenience as possible to the homeowner.

Fire Resistance: Shower areas are also subject to building codes that require certain levels of fire resistance. It's important to choose an insulation material that meets these requirements.

Energy Efficiency: While not directly related to the shower wall, it's worth considering the overall energy efficiency of the insulation. Proper insulation can help reduce energy costs by keeping the space warm in the winter and cool in the summer.

Compliance with Building Codes: It's crucial to ensure that the chosen insulation material complies with local building codes and regulations.

Now, based on the information provided, it seems that the insulation behind the tub or shower should be equivalent to that used in the rest of the exterior walls. This suggests that the insulation should provide a similar level of thermal resistance. However, the specific type of insulation can vary depending on the factors mentioned above.

An air barrier is also mentioned, which is essential to prevent moisture from penetrating into the insulation and the wall structure. This can be achieved using a cement backer board, which is a moisture-resistant board that can be used as a substrate for tile installation. It also provides a good surface for the application of mortar and tile adhesives.

Rigid foam insulation is another option that provides excellent moisture resistance and a high R-value (a measure of thermal resistance). It is also easy to install and can be used to fill irregular spaces.

Non-paper-faced drywall can also be used as an air barrier, provided it is sealed properly at the edges and seams. This type of drywall is more resistant to moisture than traditional paper-faced drywall and can be a good option for areas with high humidity.

In conclusion, the choice of insulation behind shower walls should be based on a combination of factors including moisture resistance, durability, ease of installation, fire resistance, energy efficiency, and compliance with building codes. An air barrier is also essential to prevent moisture intrusion. The specific type of insulation and air barrier material will depend on the individual project requirements and local conditions.

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The insulation behind the tub or shower should be equivalent to the insulation in the rest of the exterior walls and should be covered with an air barrier of cement backer board, rigid foam insulation, or non-paper-faced drywall that is sealed at the edges and seams to provide a continuous air seal.read more >>