Solid walls allow twice as much heat to escape compared to homes with cavity walls. So insulating them could really help to cut your energy bills.
According to the Energy Saving Trust, solid and external walls can be insulated from either the inside or the outside of the building. This could save you around £445 per year if insulated on the inside and £475 per year if on the outside.
The costs range between £5,500 to £8,500 for internal insulation to £9,400 to £13,000 for external insulation. The carbon savings are around 1.8 to 1.9 tonnes per year.
Internal insulation is carried out by fixing rigid insulation boards to the wall or building an interior stud wall filled with mineral wool fibre. The main advantage of internal insulation is that it is cheaper, but there are several disadvantages.
Internal insulation tends to reduce the internal area of any rooms in which it is applied. Not only that, but it can be disruptive during installation and skirting boards, door frames and other fittings need to be removed and then re-attached. So it’s not the most popular of all the different types of home insulation methods.
There are more advantages to be gained from external wall insulation, although of the two options this tends to be more expensive. However, unlike internal solid wall insulation, external insulation:
The cost of external insulation can be spread by combining it with any other external refurbishment work that needs to be carried out. The work may need planning permission and so you will have to check with the local council planning department.
In addition the work needs to comply with building regulations by having a thermal performance (U-value) of no more than 0.30. This measures the rate at which heat passes through the wall. In most cases you will need to apply between 60mm to 120mm of insulation.
You also should ensure that there is reasonably good access to your external walls so that the work can be carried out efficiently. Furthermore, the external walls need to be structurally sound and in good condition.
There are various forms of external wall insulation available. Those approved by the Energy Saving Trust include: