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Internal wall insulation

Internal Wall Insulation: Pros and Cons

Internal wall insulation involves the application of an insulating layer on the internal parts of a building. Types and benefits.


In recent years, the focus on the energy efficiency of buildings has significantly increased, prompting construction professionals such as contractors, architects, and engineers to seek innovative solutions to improve building insulation.

When it comes to thermal insulation, especially thermal insulation coating, the immediate association is usually with external insulation, which is undoubtedly effective, especially when applied continuously to cover all heat dissipating surfaces.

However, when external constraints such as urban planning, condominium regulations, or technical limitations prevent external insulation, how can one insulate an apartment or building?

In such cases, internal wall insulation represents an effective and cost-efficient solution to reduce heat loss and improve living comfort.

In this article, we will delve into what internal wall insulation entails, along with its advantages and challenges.

What is Internal Wall Insulation?

Applying internal wall insulation involves placing an insulating material layer of varying thickness on the vertical, horizontal, or oblique internal surfaces of a building to enhance its thermal performance, reducing heat loss, and lowering energy bills.
This technical solution is typically chosen in cases where:

  • Intervention on the external surfaces of the building is not feasible due to architectural and landscape constraints, historical facades, urban planning restrictions, or condominium regulations.
  • The building is adjacent to other constructions or has limited external spaces, making external work challenging.
  • The external walls are ventilated or have coatings that are difficult to remove.

The implementation of internal insulation requires careful execution using appropriate techniques and materials to maintain optimal thermal comfort indoors.

Types of Internal Wall Insulation

There are three main types of internal wall insulation:

  1. Dry lining insulation;
  2. Panel insulation;
  3. Foam insulation.

1. Dry Lining Insulation

Dry lining insulation involves attaching a drywall directly to the internal surface. One common approach is to construct metal-framed structures (using U and C-shaped profiles) between which various types of insulation can be inserted into the cavities. The completed inner wall is usually finished with an impermeable layer and then with plasterboards to smooth the surface. This insulation type is not recommended for narrow interior spaces due to the significant reduction in usable space caused by the structure’s thickness.

2. Panel Insulation

Panel insulation entails gluing panels made of low conductivity materials directly onto the walls or floors to be insulated, usually on the internal side. It’s often unnecessary to cover these panels with plasterboards as they can be directly fixed and finished with mesh, skim coat, plaster, and paint. Rigid materials are typically preferred for panel insulation.

3. Foam Insulation

Foam insulation is commonly used when dealing with buildings with cavity walls. When the insulation is injected into the walls, it’s referred to as cavity wall insulation. The cavity wall, also known as a “hollow wall” or “air gap,” is a structure with an unventilated air gap between the external and internal facades. The unventilated air gap acts as an insulating layer and also prevents moisture from entering the building. The foam insulation insertion is often partially invasive, requiring holes to be drilled into the walls. Complete filling of the foam into the cavity is essential to ensure insulation effectiveness.

Deforming zone

Deforming zone

Most Used Materials for Internal Wall Insulation

A wide range of insulation materials, including natural, mineral, and synthetic ones, can be used for internal wall insulation. The choice often depends on the type of intervention:

  • For dry lining insulation, materials like rock or glass wool are commonly used due to their mold and moisture resistance and acoustic insulation properties.
  • For panel insulation, cork panels are excellent due to their natural, sustainable, and renewable properties, along with being anti-mold and anti-condensation. Other commonly used materials include polystyrene and expanded polyurethane.
  • For foam insulation, initially liquid materials such as polyurethane resin, urea resin, or phenol-formaldehyde are typically used.

Pros and Cons of Internal Thermal Insulation

The installation of internal thermal insulation in a house naturally comes with both advantages and disadvantages.
The main advantages include:

  • Reduction of energy consumption leading to economic savings on utility bills;
  • Improved living comfort due to excellent thermal insulation;
  • Enhancement of the dwelling’s energy class;
  • Increased property value in the market when transitioning from a lower to a higher energy class.

It’s worth noting that the implementation of internal insulation is relatively straightforward, as it doesn’t require specific permits, initiation of building procedures, or waiting for authorizations. Additionally, it generally involves significantly lower costs compared to external insulation and offers the advantage of being applicable to individual areas within a building.
Furthermore, internal insulation also contributes to sound insulation, ensuring greater living comfort.

However, internal thermal insulation is a delicate intervention and, in general, less effective than external insulation. It may also be less efficient in managing thermal bridges, which are points of thermal discontinuity where deviations in the thermal flow occur. Moreover, it reduces the usable and living space internally.

It’s also essential to consider that certain types of internal insulation may even promote the formation of interstitial condensation between the insulation layer and the existing wall. For instance, the installation of certain types of panels or insulation in highly humid environments such as bathrooms can lead to mold formation.

Therefore, the correct design of a building’s thermal insulation is a crucial phase to ensure optimal results in terms of energy efficiency and living comfort. Before proceeding with the installation of internal thermal insulation, conducting a detailed analysis of the building project is fundamental.

To ensure proper internal insulation, it’s essential to carefully analyze the building’s structure to determine the most suitable installation conditions and material types that can provide the best design solution. Consideration of various parameters, especially the thermal conductivity of the insulating material, is essential.

In this way, the choice of insulation type is based on informed analysis, reliable simulations, and optimal thermal designs to prevent future building issues.

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