There are primarily two wall types in the domestic residential sector, solid walls and cavity walls and both can be insulated to improve the energy efficiency of a property. There are also non-traditional or hard-to-treat types which can also usually be insulated but will require more specialised preliminary works.
 

“…the better insulated a property is, the less money will be spent on heating it.”

If your property was built before the 1030s there’s a good chance it will be a solid wall construction. A good way to tell is by looking at the brick pattern. If you wall has lots of “end bricks” (which look like half bricks but are actually full, cross bricks which are laid to run from the front to the back of the wall) which are in the middle of the wall and not just around windows and doors then this is usually a reliable indicator. Typically the depth of a solid wall is obviously the width of a brick – around 9 inches.

Solid walls may sound like they should be better at keeping in the heat but unfortunately, the opposite is true. Un-insulated solid walls can lose heat twice as fast as un-insulated cavity walls but insulating them externally could save up to £435 each year and save 1770 kg/C0 2/year* (Source: Energy Savings Trust).

Put simply, the better insulated a property is, the less money will be spent on heating it.

Whilst there is no cavity to fill with insulation the good news is that solid walls and hard-to-treat properties can be insulated from the outside or, potentially, the inside.

This will cost more than insulating a standard cavity wall, but the savings on heating bills can be larger too, because more insulation can be used on the inner or outer walls.

Internal Wall Insulation (IWI) is applied to the internal walls of a building. It typically consists of the dry lining in the form of pre-insulated plasterboard or built-up systems using insulation such as mineral wool or foam sheets held in place using a studwork frame.

External Wall Insulation (EWI) involves fixing a layer of insulation material to the wall, then covering it with a reinforcement and a special type of render. The finish is usually a textured render, pebbledash or sometimes a brick slip or a brick effect render finish could be used.

These solutions can also be used in conjunction with each other, known as a Hybrid solution, where EWI is used on the front of the property and IWI at the rear. This is common if there are restrictions (i.e. listed building, conservation areas, etc) that meant an IWI or EWI system on its own would not be suitable.