If your home feels cold and draughty, or your energy bills seem higher than they should be, the chances are that your walls are losing a significant amount of heat. In fact, according to the Energy Saving Trust, uninsulated solid walls can account for up to 35% of heat loss in a typical home.
Many properties in Surrey, London and Berkshire – especially those built before the 1920s – have solid walls rather than cavity walls. This means they cannot benefit from standard cavity wall insulation, and the homeowner is left with two main options: external wall insulation (EWI) or internal wall insulation (IWI).
Both solutions work, but they suit different situations. In this article, we will explain how each option works, the pros and cons, and how to decide which one is right for your property.
What Is External Wall Insulation?
External wall insulation involves fixing a layer of insulation material to the outside of your walls, then covering it with a protective render finish. The insulation boards – usually made from expanded polystyrene (EPS), mineral wool or phenolic foam – are mechanically fixed and adhesive-bonded to the existing wall surface. A reinforced mesh layer is then applied, followed by a top coat of render in your choice of colour and texture.
The finished result looks like a freshly rendered wall, and in many cases, it can dramatically improve the appearance of a property as well as its thermal performance.
Benefits of external wall insulation include:
- Significant reduction in heat loss through walls
- Lower energy bills – savings of several hundred pounds per year are common
- Improved comfort with more consistent room temperatures
- Reduced condensation and mould risk on internal walls
- No loss of internal floor space
- Can improve the external appearance of your property
- Protects the existing wall structure from weather damage
- No disruption to the inside of your home during installation
Things to consider with external wall insulation:
- It changes the external appearance of your property, so planning permission may be required in some cases (particularly for listed buildings or properties in conservation areas)
- It increases the thickness of external walls, which can affect window reveals, sills, eaves and other external details
- It is generally more expensive than internal wall insulation
- Access may be needed around the full perimeter of the property, including scaffolding
What Is Internal Wall Insulation?
Internal wall insulation involves adding a layer of insulation to the inside face of your external walls. This can be done in several ways, but the two most common methods are:
1. Insulated plasterboard – rigid insulation boards with plasterboard already bonded to one face, fixed directly to the wall
2. Stud wall system – a timber or metal framework is built against the wall, insulation is fitted between the studs, and plasterboard is fixed over the top
Both methods are then skimmed with plaster to give a smooth finish ready for decoration.
Benefits of internal wall insulation include:
- Generally cheaper than external wall insulation
- No change to the external appearance of your property
- No planning permission required in most cases
- Can be done room by room, spreading the cost
- Rooms warm up faster because the insulation is on the inside of the thermal envelope
- Suitable for properties where external wall insulation is not practical (terraced houses with shared walls, listed buildings, etc.)
Things to consider with internal wall insulation:
- It reduces the internal floor area of each room slightly (typically 50-100mm per insulated wall)
- Skirting boards, coving, radiators, electrical sockets and light switches will need to be removed and refitted
- It can be disruptive as rooms need to be cleared for the work
- If not installed correctly, it can trap moisture and create damp problems behind the insulation
- Each room will need redecorating after the work is complete
Which Option Is Best for Your Property?
The right choice depends on your property, your budget, and your priorities. Here are some common scenarios and what we would typically recommend:
Detached or semi-detached house with plain rendered or pebble-dashed walls: External wall insulation is often the best option here. It wraps the entire building in a warm blanket of insulation, deals with any existing render problems at the same time, and leaves the inside of your home untouched.
Terraced house where only the front and back walls are exposed: External wall insulation can still work well, although you may only be insulating two walls rather than four. Internal wall insulation on the party walls (shared walls with neighbours) is not usually necessary as these walls are already partially insulated by the adjoining property.
Listed building or property in a conservation area: External wall insulation is often not permitted because it changes the appearance of the building. In these cases, internal wall insulation is usually the better option, though it needs to be specified carefully to avoid trapping moisture in historic wall constructions. Breathable insulation materials like wood fibre or calcium silicate boards are often recommended.
Property with existing damp problems: If your walls suffer from damp, it is essential to diagnose and treat the damp before installing any insulation. Insulating over a damp wall – whether internally or externally – will trap moisture and make the problem worse. At GO2 Property Services, we are both damp proofing and insulation specialists, so we can address both issues as part of the same project.
Budget is a key factor: If cost is the main consideration, internal wall insulation is typically the more affordable option, especially if you are happy to tackle one or two rooms at a time. However, external wall insulation often delivers better long-term value because it provides continuous insulation without cold bridges and protects the wall structure from the elements.
How Much Does Wall Insulation Cost in Surrey?
Costs vary depending on the size of your property, the type of insulation used, and the amount of preparation work required. As a rough guide:
- External wall insulation for an average three-bedroom semi-detached house in Surrey typically costs between eight thousand and fifteen thousand pounds, depending on the specification and finish
- Internal wall insulation for a single room typically costs between one thousand and three thousand pounds, including plastering and making good
These are ballpark figures, and we always recommend getting a proper survey and quote for your specific property. At GO2 Property Services, our quotes are detailed, transparent and provided in writing with no hidden extras.
Can You Get Grants for Wall Insulation?
There are various government schemes and grants that may help towards the cost of wall insulation, particularly if you are on a low income, receive certain benefits, or live in an energy-inefficient property. The availability of these schemes changes regularly, so it is worth checking the latest options at the time you are considering the work.
Your local council may also have information about area-specific schemes available in Surrey, Berkshire or London boroughs.
Why Choose GO2 Property Services for Wall Insulation?
We have been carrying out wall insulation projects across Surrey, London and Berkshire for over 25 years. What sets us apart is that we are not just insulation installers – we are also damp proofing, plastering and rendering specialists. This means we can handle every aspect of the project in-house, from damp diagnosis and treatment through to insulation, rendering and internal plastering.
Our family-oriented approach means you will deal with the same team from start to finish, and we take real pride in leaving every property in better condition than we found it.
If you would like to find out whether external or internal wall insulation is right for your home, give us a call on 01483 379 061. We will arrange a visit to assess your property and provide an honest recommendation along with a clear, written quote.
GO2 Property Services – damp proofing, plastering, rendering and insulation specialists serving Surrey, London and Berkshire.