In this article we cover:

  • What is external wall insulation
  • What U-values you can expect to achieve with it
  • Explainers on U-values
  • Benefits of external wall insulation
  • Drawbacks of external wall insulation

The challenge with older buildings is to stem the flow of heat lost through the fabric. This includes the floors, windows, roof and the walls. The walls make up a high percentage of the fabric area so improving the U-value on this element is vitally important. There are several methods of doing this including pumping the cavity walls with insulating beads, dry lining the internal walls with insulated plasterboard slabs and finally wrapping the house with external wall insulation (EWI).

External wall insulation is proving to be a very effective method. You are essentially wrapping all the exposed walls in a blanket of insulation with little to no thermal bridging. If we take a 1980s bugalow with a typical wall U-vale of 1.1W/sqmK and apply 100mm EWI to all exposed walls, the U-value will decrease to a very respectable 0.24W/sqmK. However, like any major home improvement, it presents both advantages and disadvantages.

What is a U-value?

The U-value represents the amount of heat lost through a 1sqm section of a building element, be it the wall, floor, roof or windows and doors. The lower this value, the less heat escaping and the more energy efficient your home will be.

Benefits of EWI

Enhanced energy efficiency: EWI significantly reduces heat loss, leading to lower energy bills and a warmer home.

 Improved appearance: The process often includes rendering, which can refresh and modernise the façade of older buildings.

Minimised internal disruption: Since the work is carried out externally, homeowners can remain in their homes without major disturbance.

 Increased property value: Improved energy ratings can increase the price of the home.

Grants available: Grants are available in Ireland from the Sustainable Energy Authority of Ireland (SEAI) to install EWI to your home. These range from €3,000 for an apartment and €8,000 for a detached house.

Drawbacks of EWI

High upfront cost: Installation is expensive and can range from €80-€120 per sqm. A typical semidetached house could expect to pay between €18,000-€25,000 depending on wall area before the grant. A grant of €6,000 can be subtracted from this total for a semi detached house.

 Planning restrictions: Listed buildings or those in conservation areas may face limitations. It is worth checking with local planning authorities before work commences on changing the façade of your home. A few cases have come up in recent times due to homeowners installing EWI to their homes.

 Potential moisture issues: Incorrect installation could trap moisture, leading to damp problems. Loss of architectural features: This can be a disadvantage as opposed to an advantage.

 Damage to EWI: The external walls will no longer serve as a ball wall for any young hurlers or footballers. The less impact the better when EWI is installed.