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Best Types Of External Wall Insulation

There are several options for external wall insulation, which can be divided into two categories: the insulation material itself and the finish or render applied over it. This type of insulation is a popular choice for solid wall buildings where internal insulation would reduce usable space and cavity insulation is not possible.

It can also be a way to enhance the appearance of a home with options such as brick-like finishes or colored renders. When considering which external wall insulation system to use, it’s important to consider factors such as cost, effectiveness, and environmental impact in addition to the goal of increased warmth.

In this article, we will explore your options and determine which external wall insulation method is ideal for you. We have divided it into two categories: the insulation material and the render that covers the system.

Types of External Wall Insulation

Insulation material

Expanded Polystyrene (EPS)

Expanded polystyrene (EPS) is a common material used for external wall insulation. It is made by packing together small polystyrene balls, similar to those found in a beanbag. EPS is popular due to its low cost, light weight, and ease of use. Its low density is due to the presence of air bubbles, which helps to prevent heat transfer through the material.

However, EPS has a relatively low fire rating of E. When used in an external wall insulation cladding system, it is typically protected by a render or other barrier with a higher fire rating. This helps to prevent fires from reaching the insulation and potentially causing damage. Despite its low fire rating, EPS can be safely used in wall insulation systems when properly installed.

Mineral Wool

Mineral wool is a type of insulation material that is similar to the rolls used for loft insulation. When used in an external wall system, it is compressed to create a rigid board. Mineral wool has a high fire resistance rating and excellent soundproofing qualities.

However, it is heavier and more difficult to work with compared to other materials like EPS or Kingspan, which can lead to higher labor costs for installation. Additionally, it may not provide as much insulation as some other materials, meaning that more may be needed to achieve the desired result.

Kingspan K5

Kingspan manufactures Kooltherm K5, an additional sort of insulation that is popular. It is a stiff, pink, phenolic board with the highest thermal performance of all the insulations on this list. It is also extremely lightweight and simple for installers to deal with.

Kingspan K5 is significantly more expensive than other materials such as EPS. If space is limited or you don’t want your insulation to be as thick, this is an excellent option, but beware of the cost.

Wood Fibre

Wood fiber is the ideal choice for external wall insulation if sustainability and thermal comfort are important considerations. We advocate the use of Pavatex, which is comprised of pine reclaimed from sawmill waste chips, shavings, and sawdust. It is very permeable, making it ideal for timber-framed homes where moisture may be absorbed and released as the house breathes.

It has the lowest thermal qualities of all the insulation types we’ve discussed, and it’s fairly heavy, but for many individuals, the eco-friendliness will outweigh these disadvantages.


There are various types of render that can be suited for different situations. In this section, we look at its use cases in the context of External Wall Insulation.


Silicone is a high-quality option for external wall insulation systems due to its breathability and ability to repel dirt and organic growth. It can also be mixed in any color, with the pigment added directly to the render so there is no need for painting or worry about chipping. Overall, silicone render is a popular choice for external wall insulation systems due to its many benefits and versatility.

Acrylic Render

Acrylic is a cheaper alternative to silicone renders for use in external wall insulation systems. It has the same flexibility and color possibilities, but its hydrophobic qualities are different. Therefore, it may require more care than renderings based on silicone.

However, it remains a good option for many individuals and can give comparable benefits at a lesser price.

Monocouche Render

Monocouche is a scratch render approach that employs conventional techniques and a single coat, making the surface far more durable than other renders. It’s premixed, so it’s a favorite among installers, but it’s relatively rigid and susceptible to cracking over time.

Sand & Cement Render

Sand and cement render is a basic rendering option made by mixing 6 parts sand with 1 part cement. It is a low-cost option, but can be prone to cracking due to shrinkage or natural movement of the structure. Therefore, it is generally not recommended for use in external wall insulation systems due to its tendency to crack and lack of durability.

Other options, such as silicone or acrylic renders, may be more suitable for external wall insulation systems due to their greater resistance to cracking and better overall performance.

Looking for a professional contractor?

If you want to insulate your property, do get in touch with us. We will assess your requirements and get back to you with a no-obligation quotation. We offer a whole range of external wall insulation services.

Looking For Plasterers In South London or Surrey?

Ralph Plastering is a highly recommended plastering company in South London and Surrey providing all aspects of plastering, dry lining, rendering and external wall insulation services.

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