Overview

External insulation involves fixing insulating materials such as mineral wool or expanded polystyrene slabs to the outer surface of the wall. The insulation is then covered with a special render to provide weather resistance. A steel or fibreglass mesh is embedded in this render to provide strength and impact resistance. External insulation is an expensive solution; however additional problems (other than poor levels of insulation) suffered by some homes such as rain penetration, poor airtightness or frost damage can be solved by an external insulation system.

Case Study Example

John has a 3 bedroom detached house with a footprint of 120 sqm (1290ft2). He has an annual heating bill of €1,600. John has solid masonry (or hollow block) walls & needs to use external (or internal) insulation for his home, he cannot use Bonded Bead, Wool or Foam. Typical costs for external insulation systems are approx €12,000 - €20,000 (excluding grant).

The Grant available from SEI to Externally Insulate John’s house was €4,000. Taking this measure resulted in John reducing his heating bill by 25%-30%, more than €520 in his annual heating bill with a payback period of between 15 to 20 years.

Sizing and Design

External insulation is typically used with masonry construction types but might also be considered as an option for upgrading timber frame dwellings. The key principle behind this insulation method is to completely wrap around the entire structural building envelope thereby significantly reducing thermal bridges which can otherwise arise where external walls and foundations connect to internal walls and the floor slab. If external insulation is being proposed for a cavity wall construction, then it would be imperative to also fill the cavity with insulation in order to avoid thermal looping occurring from the ‘cold’ unheated cavity through the internal block leaf to the inside of the dwelling. This would also reduce the visible thickness of insulation required externally. There are two options of external wall insulation, as follows:

The so-called ‘composite system’ or ‘single-skin system’ is where insulation is either stuck or mechanically fixed directly to the external face of masonry wall, reinforced with for example a plastic or glass fibre mesh and then rendered. To avoid complications regarding damages or warranty it is important to use components of one building system only. This composite system is used widely on Continental Europe as a technique to upgrade existing buildings to the Passivhaus Standard. With this single skin construction type, care should be taken that the system has Agrement Certification for insurance purposes.

The second system is where instead of the above single-skin system a ventilated cavity is created between the external cladding and the insulation, the latter of which is otherwise fixed to the exterior of the existing walls in a similar manner to the other option.

External Insulation works by adding a decorative weather-proof insulating treatment to the outside of your wall. The thickness of the insulation needs to be between 50 and 100mm and is usually installed where there are severe heating problems or the exterior of the building requires some form of other repair work providing the opportunity of adding insulation.

There are a number of systems which can be used to insulate the exterior of a house. The usual process is:
• an insulation slab is fixed mechanically to the wall
• a web is paced over this
• a polymer based weatherproof render is applied

A-Rated Energy pay close attention to details such as windows sills and window surrounds to ensure the façade of the house is unchanged.

Depending on the amount of insulation applied, the insulation of the house will increase dramatically.

To get up to the new standard of building regulations you require a minimum U value of 0.27w/m2K, to achieve a U value of 0.12 w/m2K or less you need to increase the thickness of your insulation board.

Installation

The External wall insulation system that we apply consists of the following system components.
1. Thermal insulation board adhesive
2. Thermal insulation board (EPS or XPS boards, mineral wool rigid boards or mineral wool lamellas)
3. Two-part plastic hammer set anchors
4. Base coat
5. Glass fibre mesh
6. Primer coat
7. Decorative render

Application Method

1. Insulation boards differ as far as strength characteristics, thermal conductivity and water vapour permeability are concerned. You can choose:
• EPS board, which are the most common and most cost effective type of insulation board used
• XPS board, are suitable for below ground level due to their low water absorbency and strength characteristics
• Mineral wool rigid boards have slightly better sound resistance and fire rating
• Fixing of the boards requires the use of an adhesive

2. Mechanical Fixing of Insulation Boards.

Mechanical fixing are to be installed at a pre-determined rate depending on the substrate.

3. Base Coat

The base coat depending on the insulation type should be applied to the correct thickness. Embedded in to the base coat is a resistant mesh and it is important to overlap the edges by 100mm. Additional mesh patches will be required around windows and doors.

4. Primer

Before applying the final coat, a primer is applied onto the base coat. It should match the selected final coat.

5. Final Coat Application

The final coat in an external wall insulation system is usually one of the pre-mixed decorative renders. In coastal regions it is recommended to use silicone render.

Costs and Payments

A-Rated Energy price all work on a per client basis. Pricing terms and conditions vary on the service provided.

After Sales Service

In recognition of the importance of having a first rate back up service, we have invested heavily so that our customers have access to unrivalled levels of back up service. All products offer extensive manufacturer warranties.