Comfortboard, external insulation, install, construction, exterior, home, wall

External walls, together with the roof, form the envelope of any building, protecting everyone and everything inside.

They also cover the largest surface area, making them a prime area for preventing thermal transmission. The main place where excess heat absorbed is by entering through poorly insulated walls.

With ROCKWOOL external wall insulation, living spaces can be made cool, energy-efficient, and compliant with modern building standards – as well as gaining additional benefits in terms of acoustics, indoor comfort and fire safety.

Discover the importance of insulation for exterior walls, and the positive impacts it can bring.

Why do we need external wall insulation?

Outside walls are where thermal transmission most commonly occurs in the majority of buildings.

External wall insulation can significantly moderate this – improving the building’s energy efficiency, as well as cutting CO2 emissions and reducing fuel or cooling costs.

External walls come in different shapes and forms. These range from cavity walls to rendered systems and façade cladding, for domestic, commercial and industrial buildings. Each type of external wall has its own advantages and disadvantages. They appeal to the building owner in one way or another, by assuring good energy performance that meets local requirements.

Key benefits:

  • Less thermal transmission
  • Lower energy bills
  • Protected building structure
  • Lower temperature fluctuations
  • Fewer condensation issues
  • Better acoustic level
  • Superior fire protection

Calculator and savings

Exterior wall insulation can be applied in a variety of building solutions, like External Thermal Insulation Composite Systems (ETICS), cavity wall, timber frame, ventilated façade, or metal cladding. The products themselves come in rigid slab form.

The exact costs and savings will depend on the size of the area being insulated and how much insulation is required. You can – of course – also decide to go above and beyond what is required by minimum regulations.

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.

Energy renovation can also raise the value of a building if they’re rated based on their energy performance1.

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ROCKWOOL boasts excellent thermal performance both in winter and summer. Stone wool slabs can add significant mass to the building envelope, ensuring summer comfort by keeping the heat outside. The fibres in the tightly butted slabs knit together, significantly reducing heat loss that’s caused by gaps between slabs.

Erica Bazzini

Global Product Manager, ROCKWOOL Group

Case studies

The problem

Wilmcote House flats, an iconic Portsmouth landmark in the UK, had become blighted by mould, damp and condensation.

Many people living in its three connected blocks – across 100 maisonettes and 11 ground-floor flats – were in fuel poverty, and residents were not typically heating their homes to the comfort temperature of 18°C set by the World Health Organisation (WHO)4.

The solution

Renovation aimed to ease fuel poverty by making the buildings naturally warmer and less susceptible to damp – with a target to reduce heating demand by 90 percent.

Meanwhile, a deep retrofit was launched to extend the lifetime of Wilmcote House by another 30 years.

The results

ROCKWOOL helped to reduce draughts, condensation and mould. Thermal performance and air tightness were improved thanks to the fitting of a 300/400mm zone fixed to external steel frames, which were newly assembled.

Wilmcote House project completed
It’s about future-proofing the property and moving away from the sticking plaster approach.
Due to the fabric improvements, we’re now more confident that the residents don’t need as much heating in their properties. In fact, we’re looking to take out some of the existing storage heaters so that there is a maximum of two per property — one in the lounge and one in the downstairs hall.

Steve Groves

Head of Building Maintenance at Portsmouth City Council
Read more about Wilmcote House
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Sustainability and energy efficiency

ROCKWOOL products are developed with sustainability at their heart.

One of our key aims is to help in the construction and development of energy-efficient buildings around the world – promoting comfort, safety, noise reduction and reduced emissions.

ROCKWOOL insulation can also contribute to credits for sustainable building rating schemes, BREEAM, LEED, WELL, SGBC, MGBC, TRAI, IGBC, and many more local ones.5



External walls, ETICS, MUH, multi unit, building, apartments
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Financial support

Sustainability schemes and refunds may be available for external wall insulation through tax reductions or incentive schemes. Contact our local offices for more information.

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Will external wall insulation stop condensation?
How long does external wall insulation last?
What is ETICS?
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