Solutions for Insulating Walls

ABOVE: Examples of external insulation (LEFT) and internal insulation (RIGHT)

If you live in a period property there is a good chance that there is no insulation in the walls at all, making it difficult to keep warm in the colder months, and expensive to heat. Around a third of the heat loss in a detached house is through the external walls, and if your home has solid walls with no cavity, the proportion of heat lost may be even greater (up to 50%, according to Government figures). Fitting insulation can reduce this heat loss immediately, making your home more comfortable, and according to the Energy Saving Trust (EST), saving £450-500 per year for the average three bedroom house.

If your home has cavity walls, it is relatively straightforward to blow or inject insulation material into the cavity between the inner and outer wall, typically using mineral wool fibres, cellulose fibres, mica beads or polyurethane foam. The work is undertaken by specialist contractors and can usually be done in a day or two. Once completed there is little or no visual evidence that the work has been done.

If you have solid walls, however – and if your home was built before 1930, the chances are that it has – the only way to add insulation is to fix it to either the inside or outside face of the external walls. This is more expensive than fitting cavity wall insulation, and causes far more disruption — but it’s well worth doing.

Unless a wall is being substantially reconstructed (such as the removal of all of the plaster) or involved in a material change of use, such as an attic, cellar or garage conversion, the Building Regulations do not currently enforce the addition of insulation into existing external walls when you are undertaking alterations. It is nonetheless a good idea to consider this when renovating a property, as the impact can be minimised.

Where a building is subject to a change of use, such as a barn, church, warehouse or school conversion, the Building Regulations do require the external walls to be brought up to the same standards as required of all new dwellings. It can be difficult to achieve the target U-value of a maximum 0.45W/m²K (U-value is a measure of the rate of heat loss) but fortunately, by using the Carbon Index Method, the Building Regulations allow a degree of flexibility on individual elements, such as walls or floors, providing the performance is compensated for elsewhere in the building. This means that you can, for instance, leave some panels of traditional brick or stonework visible inside a conversion to maintain the building’s original character, providing you exceed the requirements in the roof, glazing, floor and add other features that reduce the building’s overall carbon footprint.

In the following articles we look in depth at the main options for insulating solid and older timber walls.

• Internal Wall Insulation
• External Wall Insulation
• Insualting Walls: Traditional Construction

A Victorian Terrace mixes external and internal insulation solutions

The owners of this semi-detached property in Nottingham provided the perfect demonstration of how you can retrofit high levels of insulation to ordinary period houses. At the front of the building (LEFT) the 100mm insulated dry-lining is fitted inside (BOTTOM RIGHT), so the charming brick façade is unaltered. On the less sensitive side and north-facing rear wall (TOP RIGHT), where it is less important to show the period brickwork, 150mm rigid EPS wall insulation has been applied to the rear face. (Read more about this renovation...)

Further reading:

• Why Walls Need to Breathe
• How to Insulate Old Houses
• How to Give Your Home an Eco Makeover