About a third of the heat lost from an uninsulated home escapes through the walls. Since the mid-1980s, most homes have been built with wall insulation. The most common wall constructions found in Scottish homes are traditional brick or block cavity walls and solid brick walls.

In the case of cavity walls, the most common improvement is to install insulation by drilling a series of holes on the outside and injecting insulation into the cavity. This is highly cost-effective but requires a suitability assessment before installation. If the building is in a poor state of repair, over 11m high, or is severely exposed to wind driven rain, this method may not be appropriate.

In such cases, or where the wall is solid and does not have a cavity, internal or external wall insulation can be installed by adding a layer of insulation to the internal or external wall surface. Internal wall insulation is usually installed by fitting rigid insulation boards, or by building a stud wall and filling the void with insulation material, such as mineral wool.

External wall insulation involves fixing a track and layer of insulation material to the wall, and then covering it. A range of finishes are available which can improve the building’s aesthetics. These can be smooth, textured, painted, tiled, or finished with brick slips. For this method, a detailed suitability assessment must be undertaken to check the ability of the surface to carry the necessary loads.

Other wall constructions include rough stone, timber frame, steel frame, and system built, all of which can be upgraded subject to an assessment of suitability.

About a quarter of the heat lost from an uninsulated home escapes through the roof. The main forms of roof construction are traditional pitched roofs and flat roofs. The type of roof dictates which method of insulation is required.

A pitched roof is typically insulated at joist level to create a cold roof, or at rafter/roof covering level to create a warm roof. Room-in-roof insulation refers to insulation that’s used to create a warm attic space in a home.

A cold roof is typically insulated by laying 270mm insulation between and over the joists at ceiling level. It must be adequately ventilated; services such as downlighters must be protected and pipework and loft hatches insulated. A warm roof has the insulation fitted directly below the roof covering, between the rafters.

Room-in-roof insulation solutions are more complex and involve fitting insulation to provide a continuous thermal envelope around the room space. The term ‘thermal envelope’ refers to the shell of the building acting as a barrier to unwanted heat between the interior of the building and the outside conditions. This minimises heat loss by securing areas such as the window and door reveals. The final design will rely on the specific layout, which could include areas of cold roof space. This emphasises the need for effective moisture control.

Although less common, flat roofs can also be treated by placing insulation on top of a vapour control layer above the roof decking, immediately below the waterproofing.

The ground floor can account for 10% to 20% of heat loss from the building envelope. This could be a result of gaps in the floorboards, around the floor perimeter, or because of gaps around the pipework.

Adding insulation can improve the U-value and eliminate any draughts to improve the home’s energy efficiency. The floor of the property impacts which insulation is needed. The most common floor types are:

• Suspended timber
• Beam and block
• Solid concrete

Suspended timber floors are usually insulated by fixing wool between the joists. A building assessment is needed to identify any condensation issues, high moisture content, or poor ventilation, prior to installation.

Beam and block and solid concrete floors can be retrofitted with insulation by fixing rigid insulation boards on top of a damp proof membrane and finishing with either a screed or a floating floor.