Wall Insulations


Understanding Wall Insulation Systems

In recent years there has been a huge increase in social and political pressure to minimise unnecessary energy consumption.

Diminishing fossil fuels and rapidly increasing energy bills are a cause for concern around the world. Heating and cooling buildings is a considerable cost for both domestic and commercial property owners.

Significant, ongoing savings can be made if the entire building is insulated properly. External wall insulation (EWI) systems help reduce energy consumption and
energy costs.

Heat transfer through a wall is known as thermal transmittance and measured using U-values.

The materials used, number of windows and doors, just about everything involved in the construction of a building, has a direct impact upon heat loss and heat gain.

The UK Building Regulations provide maximum U-values across the UK and Eire.

There are 3 typical approaches to insulating walls: internal, cavity and external wall insulation.

We believe that the best possible building performance can only be realised if walls are externally insulated.

Internal Wall Insulation

  • Rooms can be heated quickly.
  • Added insulation thickness reduces the internal room dimensions.
  • Structural wall is cold and potentially damp, increasing the risk of condensation
  • Installation is disruptive for building occupants.
  • Exposure to cold bridges, resulting in condensation, damp and mould.

Cavity Wall Insulation

  • One of the most common building insulation methods.
  • Cavity construction is expensive and time consuming.
  • Thicker wall construction reduces the internal room dimensions.
  • Limits options for thermal upgrades in the future.
  • Outer leaf construction isn’t insulated or protected, increasing the risk of condensation and freeze / thaw damage

External Wall Insulation

  • Structural wall is warm and dry, increasing thermal performance and reducing building maintenance.
  • Removal of cold bridges reduces the risk of condensation, damp and mould.
  • The heat retention capability of the existing wall is fully utilised.
  • Lightweight construction methods can be used, allowing for fast installation.
  • Condensation can be eliminated, irrespective of climate conditions.
  • Eliminates cracking caused by thermal expansion and contraction, even in mixed blockwork.

Key Insulation Terms

Cold Bridge

Wherever a building element crosses through an externally-facing wall (e.g. floor and ceiling joints; door and window frames) heat can escape through the element. This is especially a problem in concrete and steel framed buildings. Where the temperature of the surface falls below the condensation point of the surrounding air, this can lead to condensation and mould growth inside the building, which is harmful to the health of the building’s occupants.

Cold Spot

Any part of an exterior-facing surface with a significantly lower thermal resistance than the surrounding area. This can lead to a blotchy appearance on a facade, particularly early in the morning.


A calculation to determine how much thermal energy in Watts (W) is transported through a building material with the size of 1m² at a temperature difference of 1 Kelvin. The unit of measurement for U-values is W/(m²K). Achieving low U-values reduces the energy used to heat a building, which reduces energy bills and contributes towards saving energy. U-Values are measured in accordance with BS EN ISO 6946:1997.

Building regulations

In the UK and Ireland, ongoing efforts to limit the use of natural fuel resources have been implemented through the UK Building Regulations. As part of the assessment, the Regulations specify maximum U-Values for new buildings. These values are different across the United Kingdom and Ireland, and are currently:

Part L (England, Wales, N. Ireland) – 0.35W/m²K
Part J (Scotland) – 0.3-0.27W/m²K
Part L (Eire) – 0.27W/m²K

Download the Part L1A Guide 2010

Download the Part L1B Guide 2010

External Wall Insulations can explain to you in simple terms what it needs to be done to get your home warm and energy efficient. We are just a call away.

Contact Us

External Wall Insulations

Address: 2nd Floor, Old Bank Chambers, 39 Station Road, Horley, Surrey, RH6 9HW

Tel: 01293 820350

Email: info@external-wall-insulations.co.uk



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We would be happy to help and advise you on the type of external wall insulation that best meets your needs.

Our site surveys and advice are completely free of charge.

We cover all areas of Sussex: Bognor Regis, Horsham, Billingshurst, Brighton, Hove, Littlehampton, Arundel, Worthing, Henfield, Shoreham-by-Sea, East Preston, Hove, Fareham, Pulborough, Lancing, Epsom, Burgess Hill, Banstead, Rudtington, Crawley, Pound Hill, Woking,