Benefits of external insulation

Houses without external insulation lose around one third of heat through walls, so it is worth insulating them, this will retain heat and save you money on your heating bills.

External insulation will increase
your home’s energy efficiency

According to the Energy Advisory Associates external insulation is even more important than internal insulation; “It is much more durable than internal insulation, keeps the walls extremely warm and you do not use up valuable living space as you can easily do installing internal insulation”.

Before deciding to invest in external insulation, you will need to understand what type of walls your house has. There are two types; solid walls and cavity walls. If your home was built from 1920 onwards it has probably got cavity walls, which involve two layers of wall with a small gap (cavity) between them. The cavity acts as a barrier to reduce heat loss. Solid walls (usually found in properties pre-1920) have no such gap, meaning that more heat can pass through them – up to twice as much. The good news is that both types of walls can be insulated.

Advantages of external insulation

• Is installed without disruption to the home and does not get rid of any valuable living space
• Improves the appearance of aging exterior walls (planning permission may be required so check with your local council before undertaking any work)
  
• Fills in any cracks in brickwork and consequently gets rid of any draughts they were causing
• Prolongs the lifetime of a home by protecting the brickwork.
  
• Reduces condensation on internal walls and also discourages damp

Disadvantages of external insulation

• Can be more expensive then internal insulation. So for that reason, it is ideally installed at the same time as other refurbishment work to outer walls to save money
• Demands good access to the outer walls so that the installers can apply the insulation
• Can’t be done if the outer walls are structurally unsound and cannot be repaired

How much does external insulation cost?

The following costs are advised by the Energy Saving Trust and are based on an average gas heated semi-detached three bedroom house.

Solid wall Insulation

Installed cost: £10, 500 - £14, 500
Saving per year: £400
Co2 saved per year: 2.1 Tonnes

Cavity wall insulation

Installed cost: £250
Installed payback: two years (approximately)
Saving per year: £115
Co2 saved per year: 610kg
(The installed cost includes the subsidy under the Carbon Emissions Reduction Target)

External insulation for solid walls

Cavity wall insulation can
save you money

Is this suitable for your home?

It will be more cost effective if your exterior walls need re-rendering anyway. Remember you may need to get planning permission, especially if you live in a listed property or it is located within a conservation area.

How is a solid wall insulated externally?

A layer of insulation material is attached to the walls using mechanical fixings along with adhesive it is then covered with render or cladding. To prevent condensation, recessed areas around the windows must be insulated as well as the walls. The end result can be smooth, textured and painted, tiled, panelled, pebble-dashed or finished with brick slips. As this will cover the original appearance make sure you check with your local council if you need planning permission.

External insulation for cavity walls

Is this suitable for your home?

Your home will be suitable for cavity wall insulation, providing the external walls are unfilled cavity walls. If your home was build in the last 10 years it is probably already insulated. All masonry/brick work of your property must be in good condition, and the cavity must be at least 50mm wide.

How is a cavity wall insulated externally?

Cavity wall insulation can be done with one of three materials; mineral wool, beads/granules or foamed insulants. All three are manufactured according to the strict British Standards. Foam insulation must be certified by the British Board of Agreement and installed following guidance.

To insulate the walls, your installer will drill small holes around the outside of your home, and then using equipment ‘blow’ the insulation into the gap (cavity). Once the insulation is packed in, the installer will fill in the holes and you will barely be able to see them.

Questions to ask the installer

External insulation should only be installed by a professional; it is not a task most homeowners would be able to complete safely and effectively.

• Can I see examples of previous work?
  Ideally they should have a few before and after photos of similar work they have carried out.
• What is the best way to install external insulation in your home to achieve good energy performance?
  It should be to a U-value of around 0.35W/m2K. The U-value of a wall is a measure of the rate at which heat passes through it and so is a measure of how well insulated the wall is and is expressed in terms of “Watts per meter squared-Kelvin” (W/m2K). The lower the U-value, the better the performance of the insulation and the less it will cost to heat your home.