TrustMark Internal Wall Insulation Installers

What is Internal Wall Insulation?

Internal wall insulation refers to the process of adding insulation material to the interior surfaces of internal walls within a building. It is specifically for solid internal walls with no cavity. The primary goal is to enhance the thermal performance of your walls, reducing heat loss by up to 25% and improving energy efficiency. The internal wall insulation method is typically used in existing buildings where external insulation or cavity wall insulation is not possible due to it being a solid wall.

The process involves fixing insulation boards or batts to your internal walls, and installing a choice of insulation material such as rigid insulation boards, mineral wool, or other sustainable insulation materials. Once installed, internal wall insulation is often covered with plasterboard or other finishing materials to create a smooth and aesthetically pleasing surface.

How does Internal Wall Insulation Work?

Internal wall insulation works by adding an insulating layer to the interior surfaces of external walls within a building. This layer helps to reduce heat loss, improve energy efficiency, and enhance thermal comfort within the living space. Here’s a basic overview of how internal wall insulation works:

Reducing Heat Loss:

  • The insulation material slows down the transfer of heat through your walls. This results in reduced heat loss from the interior of the building to the exterior, especially during colder months.

Thermal Comfort:

By maintaining a more stable indoor temperature, internal wall insulation contributes to improved thermal comfort for occupants.

Energy Efficiency:

  • Reduced heat loss means that the building’s heating system doesn’t need to work as hard to maintain a comfortable temperature. This can lead to increased energy efficiency and potentially lower heating costs.

Preservation of Interior Space:

  • Unlike external wall insulation, which affects the appearance of the building’s exterior, internal wall insulation preserves the external appearance while providing the benefits of improved thermal performance.

It’s crucial to note that internal wall insulation should be installed carefully to address potential issues like thermal bridging and moisture management. Professional advice and compliance with building regulations are essential to ensure effective and safe installation.

Diagram showing the layers of an insulated internal wall

Benefits Of Internal Wall Insulation

Internal wall insulation improves your homes overall insulation by up to 25%, internal wall insulation offers several benefits, such as:

By reducing heat loss through walls, internal insulation helps to maintain a more stable and comfortable indoor temperature, potentially lowering energy consumption for heating.

Warmer internal surfaces can contribute to increased thermal comfort within the living space.

Improved insulation can lead to reduced heating costs, making the building more energy-efficient and cost-effective.

Unlike external wall insulation, which alters the appearance of the building’s exterior, internal insulation preserves the external appearance while improving thermal performance.

Internal wall insulation can help manage moisture issues by creating a barrier that prevents warm air from condensing on colder surfaces. Proper installation and ventilation are crucial to address potential moisture concerns.

Insulation materials used in internal wall insulation can also contribute to sound absorption, reducing the transmission of noise between rooms and from external sources.

Meeting or exceeding building regulations for energy efficiency is essential for new constructions and renovations. Internal wall insulation helps achieve these standards, ensuring compliance with regulatory requirements. Internal wall insulation is also one of the main criteria for improving your homes EPC rating.

Internal wall insulation improves your homes EPC rating
It's important to note that the effectiveness of internal wall insulation depends on proper installation and consideration of factors such as insulation material, thickness, and potential thermal bridging.

Internal Wall Insulation installation

The insulation installers Insulation Scotland partners with are well versed at installing internal wall insulation on solid walls. Like most home insulation, proper installation is everything to achieve the full benefits of internal wall insulation. The installers we work with adhere to the following installation process when fitting internal wall insulation:


Before installing internal wall insulation, the existing wall surfaces are typically assessed for suitability. Any issues such as dampness or structural problems may need to be addressed first.

The appropriate insulation material is chosen based on factors like thermal performance, moisture resistance, and the available space for installation. Common materials include rigid foam boards, mineral wool, or other insulation materials.

The selected insulation material is fixed to the interior surfaces of the external walls. This can be achieved by attaching insulation boards or placing batts between timber or metal studs.

Gaps and joints between insulation boards are sealed to prevent air leakage, which can compromise the effectiveness of the insulation. This helps create a continuous thermal barrier.

Once the insulation is in place, finishing layers are added to create a smooth and aesthetically pleasing surface. This often involves fixing plasterboard over the insulation.

It’s crucial to note that internal wall insulation should be installed carefully to address potential issues like thermal bridging and moisture management. Professional advice and compliance with building regulations are essential to ensure effective and safe installation.

Best Material For Internal Wall Insulation

The best material for internal wall insulation depends on various factors, including thermal performance, space constraints, moisture resistance, and budget considerations. Here are some common materials used for internal wall insulation:

Rigid Insulation Boards:

Advantages: Good thermal performance, lightweight, and easy to install. Some types, like extruded polystyrene (XPS) and polyisocyanurate (PIR), offer high insulation values.

Considerations: May require additional fire-resistant coatings, and careful installation is needed to avoid thermal bridging.

Mineral Wool (Rockwool or Glass Wool):

Advantages: Provides good thermal and acoustic insulation, fire-resistant, and moisture-resistant. Can be used in various forms, including batts or rolls.

Considerations: Requires careful installation to avoid gaps and compression, and it may irritate the skin during installation.

Cellulose Insulation:

Advantages: Made from recycled paper or other plant fibres, good thermal performance, and can be blown or injected into wall cavities.

Considerations: Requires professional installation, may settle over time, and may not be suitable for areas prone to moisture.

Spray Foam Insulation:

Advantages: Provides an effective air seal, good thermal performance, and can be applied to irregular surfaces.

Considerations: Professional installation is essential, and it may expand over time, causing issues if not applied correctly.

Reflective Foil Insulation:

Advantages: Reflects heat, effective in reducing radiant heat transfer, and can be used in combination with other insulation materials.

Considerations: Works best in conjunction with other insulation, may not be sufficient as the sole insulation material.

Plasterboard with Insulation Backing:

Advantages: Integrates insulation into the plasterboard, providing a finished surface.

Considerations: Thickness may be limited, and it may not provide as high thermal resistance as some other materials.

As you can see there is lots of choice, generally speaking mineral wool, rigid insulation boards and foil insulation are best for internal wall insulation.


Knauf Mineral Wool Insulation


(PIR) Rigid Insulation Boards

Insulation Scotland

Internal Wall Insulation Installers Midlothian

Numerous insulation installers and companies offer internal wall insulation services throughout Scotland. It is advisable to conduct thorough research to ensure the selection of the most suitable installer for your home insulation needs. Additionally, checking online ratings and reviews is essential, and opting for a well-established insulation company is recommended.

Internal Wall Insulation Grant Midlothian

Internal wall insulation or IWI as it’s commonly known in the industry is amongst the most common type of home insulation where a government grant is awarded to fund the cost. 

People often look for a loft insulation grant or a cavity wall insulation grant which may not always be available or more accurately, it won’t always be the top priority to improve your homes EPC rating.

All grants are available through Home Energy Scotland, however, we are happy to assist you with your application and can then install your internal wall insulation if you are awarded funding.

For more information, visit the Home Energy Scotland website or call them directly on 0808 808 2822.

ECO Flex Internal Wall Insulation Grant

The ECO flex or local authority flex is another grant available for internal wall insulation. This is only applicable in North Lanarkshire, South Lanarkshire and Renfrewshire council areas where our partners are approved installers. 

The ECO flex provides funding for people who are not on benefits but earn less than £31,000, who’s home EPC rating is less than D and who meet other criteria.

Insulation Scotland

Approved Internal Wall Insulation Installers

Get an Internal Wall Insulation Quote

Please fill out the contact form below so we can arrange a no obligation internal wall insulation survey. Please allow up to 48 hours for one of our representatives to contact you to discuss on the telephone.

Instant Quote in Midlothian

Please call us to discuss your requirements, if you have pictures of your walls, loft, roof or home layout please provide these to speed up the process.
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