Cavity Wall Insulation

Homeowners lose up to 33% of heat through external walls. Wall insulation can improve the thermal envelope of your home and reduce your energy bills. We sell cavity insulation boards and cavity insulation slabs that have excellent thermal properties. According to the Cavity Insulation Guarantee Agency (CIGA), if you have cavity wall insulation installed, it can lower global warming and heat loss. Industry-leading manufacturers like Celotex, Knauf Insulation, and EcoTherm create insulation products that are designed to last. Our range of partial fill cavity wall and full fill cavity wall insulation boards and insulation slabs are available in different thicknesses and sizes.

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What Is Cavity Wall Insulation?

Cavity wall insulation is designed to fill the space between two masonry walls. They can even be friction fitted between joists and placed on flat surfaces that need to be filled. Cavity boards and slabs trap heat inside your home. They have excellent thermal properties. Some cavity insulation slabs and boards have thermal conductivity values as low as 0.018 W/mK.

There are lots of different types of cavity insulation. You can purchase glass mineral slabs, phenolic boards, and PIR boards. PIR is one of the most popular types of insulation for people who want a strong performance cavity insulation board.

How Does Cavity Wall Insulation Work?

Like all other types of insulation, cavity boards and slabs act as a barrier between the outside of the building and the inside. Wall cavity  insulation contains materials that do not easily conduct heat. The lower the thermal conductivity of the insulation (measured in W/mK), the better it is at reducing heat loss.

Cavity walls are comprised of two masonry walls. They are referred to as ‘cavity’ walls because there is always an empty space or unfilled cavity walls between the two walls. Lots of homeowners invest in cavity insulation to combat the loss of heat from their homes through these wall cavities. When you invest in our cavity wall products, you can save money and stay toastier for longer.

Partial Fill Cavity Insulation

Partial-fill insulation leaves a 25mm or 50mm gap between the insulation and the external leaf. Even if moisture makes it through to the outer leaf, there is very little chance that it will bridge through to the internal structure. Lots of local authorities require new build properties to have partial fill insulation inside masonry walls.

Full Fill Cavity Insulation

Full fill cavity insulation is quicker and easier to install. You do not have to spend time securing the boards or slabs in place. Full fill slabs and boards are designed to fit snugly between the masonry walls, which means that you can simply place them in the space.

Filling the entire cavity reduces the likelihood of future problems and better protects your space against costly heat loss. You do not have to worry about leaving ‘snots’ of mortar or debris in the space between the masonry walls. Some homeowners will not be able to install cavity insulation if their building code does not allow it.

Types of Cavity Wall Insulation

There are two main types of cavity wall insulation that can be put between solid walls.

Cavity Wall Insulation Slabs

Cavity wall insulation slabs are commonly made from glass wool. These materials are usually made from at least a third of recycled materials. Unlike rolls of insulation, slabs are flat rigid rectangles that are far easier to install. They are also known as cavity batts.

Lots of people choose Knauf DriTherm products for reliable cavity slabs. These glass mineral wool slabs are water repellent. They are also rated A1 on the Euroclass scale, meaning that they are anti-combustible. They are even BBA certified for use in exposure zones.  Knauf DriTherm cavity wall slabs are a full fill solution, meaning they fill the cavity completely without leaving an air gap.

Cavity Wall Insulation Boards

Cavity wall insulation boards are made from foam that is sandwiched between two aluminium facings. They are sometimes referred to as insulation foam boards or rigid foam. They are available in a range of sizes and thicknesses. You can slot cavity wall insulation boards in place and secure them with ease.

PIR foam is one of the best thermal insulators available on the market. PIR has a thermal conductivity value of just 0.022 W/mK. Celotex CW4000 products are the best cavity wall insulation for people who want all the benefits of PIR. They are available in thicknesses ranging from 50mm to 100mm and have low emissivity foil facings. The Celotex CW4000 is a range of partial fill cavity insulation, which means that there needs to be an air gap between the insulation and the external leaf.
There is also polyurethane foam and polystyrene beads cavity wall insulation material.

Frequently Asked Cavity Wall Insulation Questions

Does Cavity Wall Insulation Reduce Noise?

Cavity wall insulation is not specifically designed to reduce noise pollution and heating bills. The cavity wall slabs and boards that we stock are designed to reduce the transmission of heat. Despite this, you might still experience less sound pollution as a result of cavity insulation.

Sound waves travel through air from one material to another. In cavity walls, there is a gap between the two masonry walls. By filling the gap, you will create a barrier that the sound waves have to move through. The waves will dissipate, and less sound will reach the material that is on the other side of the insulation. 

If you are looking for insulation that reduces sound transmission, browse through our acoustic insulation rolls.

Is Cavity Wall Insulation Fire Resistant?

The fire resistance of insulation materials is measured on the Euroclass scale. This scale was created to regulate the classification of insulation materials in Europe. The scale starts at A1 (non-combustible) and ends at F (combustible). Different types of cavity wall insulation have different Euroclass ratings.

●     Celotex CW4000 - rated E, partially combustible

●     EcoTherm Eco-Cavity - rated F, combustible

●     Kingspan KoolTherm K108 - rated F, combustible

●     Knauf DriTherm - rated A1, non-combustible

An F rating on the Euroclass scale does not mean that you cannot use these products. All these slabs and boards still provide premium protection against heat transmission. If you are concerned about the fire rating of these products, you can use a build-up of materials that have better heat protection.

Is Cavity Wall Insulation Safe?

Cavity insulation boards and cavity insulation slabs are safe to use. It is a common misconception that some insulation materials, in particular fibreglass, are detrimental to health. Many people think that cutting fibreglass insulation can release dangerous particles into the air. Fibreglass cavity wall insulation is only dangerous when it develops mildew and the spores become airborne.

As long as you take the proper precautions when installing and protecting your insulation, you do not have to worry about dangerous airborne bacteria. Always consult with a professional cavity wall install before installing cavity wall insulation.