Cavity Wall Insulation

Cavity wall insulation is a common solution for heat loss in buildings throughout much of the world.

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Cavity Wall Insulation

Cavity wall insulation is a common solution for thermal transmission in buildings throughout much of the world.

Buildings constructed since the early-to-mid 20th century typically have an outer wall with a cavity. Originally designed to better prevent water from coming through, since the 1960s and 70s these have often been filled with insulation – primarily for thermal performance.

Cavity wall insulation can bring additional benefits by reducing carbon emissions – and improving health and indoor comfort¹.

Without proper insulation, in hot climates, heat will easily come in, increasing the need for cooling. This will lead to higher energy bills.

Discover more about the benefits, products, and installation methods of ROCKWOOL cavity insulation today.

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Why do we need cavity wall insulation?

Fitting insulation for cavity walls is among the quickest and most cost-effective ways to improve energy efficiency. Whether it's slabs for new builds and extensions.

Materials with strong thermal insulation properties are key to delivering effective external walls². An uninsulated cavity will cause a lot of heat gained during a hot period.

Cavity wall insulation acts like a blanket that stops cool air from escaping. It retains the cool air and spreads it around the internal space.

In hotter climate conditions, insulation can help keep the home cool or reduce the need for air conditioning, assuring the property maintains a pleasant temperature and doesn’t overheat.

Key benefits include:

Improved energy efficiency and warmer surface temperature on the inside of the outer wall
Enhanced fire safety – especially around openings, preventing a fire from spreading through the cavity
Reduced cooling costs
Quick and easy installation

Calculator and savings

The exact cost of installing cavity insulation and the energy savings it can bring will depend on property size and type – as well as local building practices and energy supply.

Stone wool insulation can be installed as partial or full fill, with the amount required determined by the number of walls and the type of material used.

Use our ROCKWOOL U-value calculator to determine the thermal performance of the building’s walls and possible cost savings. For more details on technical specifications, visit our ROCKSPEC Specification Toolkit.

Learn about energy efficiency

Why choose ROCKWOOL solutions?

We offer two main types of wall cavity insulation. Each has its own benefits:

Cavity slab - Flexible surfaces adjust to irregular inner walls and sides, knitting perfectly together. This avoids gaps behind the insulation and open joints, which could lead to thermal losses. In addition, the material does not shrink or expand due to temperature changes – maintaining its shape under all conditions.

ROCKWOOL cavity wall insulation also uses the power of stone to create resilient, long-lasting and effective solutions.

Key benefits include³:

Thermal consistency - maintains a steady temperature
Fire resilience - adds to the fire safety of the entire building
Water repellent - prevents rainwater coming through the construction
Reusable and recyclable - sustainability at the forefront
Sound absorption - improves acoustic performance
Robust and adaptable - lifelong steady performance

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Using natural air to insulate, thermal performance does not deteriorate over time. Studies show a stable performance even after more than 55 years. The material will last the lifetime of a building.

Roger Peeters

ROCKWOOL Group Product Manager

Case Studies

The challenge

Silken Park in west Dublin, Ireland, was conceived as a new build housing development designed to offer cost-effective, low energy housing that would minimise environmental impact. The homes needed to be comfortable, while still delivering strong thermal performance.

The solution

To create a cost-effective building envelope, Silken Park saw a ‘fabric-first’ approach to construction. This aimed to ensure all buildings were airtight and well insulated, meeting the latest building regulations and Passive House standards. Several ROCKWOOL cavity insulation products were used.

The results

Our environmentally friendly and effective insulation ensured that the building fabric across all units in Silken Park saw significantly reduced heat loss.

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By combining simple wall construction, good solid windows, air tightness, ventilation, and above all, high levels of insulation, we will have a very happy customer, with a healthy home and – most importantly – very low energy bills.

Barry Durkan

New Homes Director, Ecofix UK

Applications

Insulation

Timber Frame Insulation | ROCKWOOL Asia

Timber frame insulation provides strong acoustic, fire resistant and thermal properties. Improve your timber frame wall insulation with ROCKWOOL solutions.

Insulation

External Wall Insulation | ROCKWOOL Asia

External walls are key for combatting heat gain in buildings. Improve energy efficiency – and gain other benefits – with ROCKWOOL external wall insulation.

Insulation

Internal Wall Insulation | ROCKWOOL Asia

Internal wall insulation reduces heating bills and boosts indoor comfort. Discover the benefits and strengths of ROCKWOOL wall applications today.

Installation

With cavity wall slab insulation, the amount required matches the ft² area of the property’s walls (minus openings such as doors and windows). In new build properties these are usually installed by the contractor or bricklayer.

Working out the amount of loose fill cavity wall insulation is more complex – this is blown into the cavity through tiny holes in the wall by specialised installers. The installed density needs taking into account, so contact our installers directly to measure what you need.

Key tips:

Use a registered installer - they will check your property for suitability and recommend the best type of insulation to use.
Choose partial or full fill cavity insulation - it can depend on your local regulations or building traditions which is most suitable.
Measure your property - make sure you have enough material by measuring your cavity walls first. Insulation times will depend on the size of the property and ease of access.

Inspiration and guides for professionals

Are you a professional?

Our sales package that can boost your business includes:

Guide on how to sell a premium job
Tips & tricks to do an expert installation
Advice on effective communication with customers
Frequently asked questions by other professionals and customers
Boost your skills by watching our installation videos

Sustainability and energy efficiency

ROCKWOOL cavity wall insulation is focused on sustainability. Our key aim is to assist with the construction and development of energy-efficient buildings, using effective materials from a sustainable source.

Our products help property owners and industry professionals comply with market requirements - and go beyond them. We strive to work towards NZEB (nearly zero-energy buildings) through highly energy efficient designs that promote indoor comfort and quality.

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ROCKWOOL cavity products help enhance the thermal comfort, heating and air quality of any building.

By using the latest innovative emissions control technology, we minimise the environmental impact of producing stone wool insulation too. Over the lifetime of its use, our building insulation will save 100 times the carbon emitted in its production⁴.

Our products are also assessed and certified via Environmental Product Declarations (EPDs)⁵ that can be found on local websites or obtained from our Technical Support teams.

Learn about Net Zero Energy Building