Keep The House Warm

Exterior Wall Insulation

Solid Wall Insulation Guide

exterior insulationIf you live in a home with solid walls it is estimated that the loss of heat in your property through the walls will be around 45%.

Unlike properties with cavity walls which have a gap between the two layers that can be filled with insulation to retain warmth and save energy, solid walls are a single brick or stone wall and therefore warmth cannot be retained in the building.

Solid wall insulation has been available for many years and is a solution for properties which do not have cavity walls or are considered difficult to treat. Although this type of insulation is more costly than loft and cavity wall insulation due to the process involved, the potential savings to be made are far greater reaching £460* per year for internal wall insulation and £490* per year for external wall insulation.

Do you have solid walls?

Older houses usually built before the 1920s will have solid walls.

The easiest way to work out if your property has solid walls is to view the exterior brickwork. If you can see an alternating pattern it is most likely that your property has solid walls.

If your property is rendered or the brickwork has been covered the next step is to measure the width of the wall. Measure the width at a door or window. If the wall is less than 260mm thick, it is a good indication that it is probably solid. There are however some exceptions to this rule as stone buildings will measure thicker than 260mm but will still be solid.

MeasureAnnual SavingTotal cost including InstallationCarbon Dioxide Saving Per Year
Internal Around £460 £5,500 to £8,500 1,800kg
External Around £490 £9,400 to £13,000 1,900kg

Although the cost of installing solid wall insulation is more costly than cavity wall, the financial savings per year are considerably more.

Solid walls can be insulated from the inside or the outside.

Internal wall insulation

Insulating a wall internally is usually considered less disruptive than the external option and can be done on a room by room basis.

Usually there are 2 main ways to insulate.

Rigid insulation boards are foamed boards backed with plasterboard and are fixed directly onto the walls using adhesive, strategically placed fixings and plaster. Varying in thickness from 25mm to 100mm depending on the materials used any items such as mirrors and pictures that need to be placed on the wall must be attached using special fixings.

Alternatively a stud wall with mineral wool fibre placed behind it can be built. Vertical batons are fitted to the wall, mineral wool insulation at least 120mm thick is placed between the batons, sealed and plastered over.

A stud wall is the best option to use where the prepared wall is uneven or requires levelling before installation. A stud wall is not as strong as using insulation boards so will be unsuitable in areas that require heavy fittings such as kitchens.

For both systems the surface of the wall must be carefully prepared, sealed and any potential damp issues must be addressed before installation.

It is worth noting that due to the thickness of the insulation installed, the floor space will be reduced slightly.

Exterior Insulation

To insulate an external wall a layer of insulating material is fixed to the wall and rendered.

External wall insulation can be achieved without any internal disruption or damage.

Insulating boards of around 25-50mm thickness are attached to the exterior walls using adhesive and special fixers. The boards are then covered with a protective, re-enforcing mesh which is then rendered.

The render comes in a variety of finishes to suit the individual requirements of the customer.

Like internal wall insulation, the wall must be prepared before installation takes place and any damp issues must be addressed.

As external wall insulation will change the appearance of a property it is worth checking if planning permission is required before work commences.

Keeping the costs down

Although the main disadvantage of solid wall insulation may be the cost to install, the main advantage is the savings that can be made on energy bills.

Internal wall insulation is generally cheaper to install than external wall insulation but can be disruptive and internal floor space will be reduced.

External wall insulation can be fitted with little disruption to the household however planning permission may be required.

To keep costs down it may be more financially viable to consider solid wall insulation whilst alternative home improvement work is being undertaken on the house.

Finding an installer

It is important that when fitting solid wall insulation it complies with current building regulations and meets the thermal performance requirements with approval from the local Building Control Office.

Next Steps

To speak to Keep The House Warm about solid wall insulation call 0800 118 2755 or click here to contact us through this website.


* Energy Saving Trust