A Guide to Wall Insulation

A Guide to Wall Insulation
Posted in: Guides, Insulation

A Guide To Wall Insulation

Most homeowners are probably losing around 35% of the heat in their homes from the walls. There is a solution however, you can have your walls insulated meaning your home will become more energy efficient and help reduce your energy bills.

How Does Wall Insulation Work?

Cavity wall insulation works by injecting mineral fibre or using PIR/Phenolic/Mineral wool slabs. Solid wall insulation usually comes in the form of specially treated rigid boards or rolled material. Whichever material is used works to prevent the heat from escaping through the insulation. It traps the heat with tiny air pockets. This helps the warm air stay inside the home making your central heating system run more efficiently and thus reducing your energy bills.


What Type of Walls Do I Have?

The age of your house can give you a clue as to what type of walls you are likely to have. This is because most properties that were built before the 1930s are probably going to have solid walls. Between the 1930s and the 1980s, many of Britain’s homes were built with cavity walls. After the 1980s it is hi

Loft Insulation

ghly likely that you have cavity walls and they may already be insulated.

Another way to tell what type of wall you have is by looking at the brickwork. If the bricks appear long all the way down the wall, then you most probably have a cavity wall. If some of the bricks appear to be shorter in the middle of the wall, then it is probably solid. If while you’re looking you see small holes have been drilled into the wall at some time, this could mean you already have cavity wall insulation.

Finally, a third way of looking is to measure the thickness of your walls from outside a window or door. If your walls are 30cm or more then you could have cavity walls. If they are less than 30cm it is likely that you have solid walls.


Can You Add Insulation to Existing Walls?

Yes. You don’t need the property to be a new build. Insulation can be added to existing walls both externally and internally.


What Types of Wall Insulation Are There?

There are several types of wall insulation for both cavity and solid walls:

Cavity Wall

Cavity wall insulation is the easiest and cheapest way to insulate your walls. It can be done using three different types of insulation which are:

  • Blown Mineral Fibre/Mineral wool slabs – This is made up of rock wool or glass wool which is spun and dried into fibres. The fibres are then treated with water repellent before being blown into the wall cavity.


  • PIR Boards- Polyisocyanurate, also referred to as PIR, is a thermoset plastic typically produced as a foam and used as rigid thermal insulation.
  • Phenolic boards - These boards are manufactured by a process in which a plastic foam forms an insulating core between two flexible tissue faced layers. It has a high closed cell content and fine cell structure. Rigid phenolic insulation is produced by mixing high solids and phenolic resin with a surface acting agent.

Solid Wall Insulation

You can still insulate your wall if it is solid. There is internal insulation, which means you insulate from the inside. It is a cheaper option, but it does mean that your rooms will become slightly smaller. External insulation is more expensive because it is more labour intensive.

If you insulate from the outside, then usually rigid boards or mineral fibre are fixed to the outside walls and then a layer of render or cladding is added. This may change the appearance of your exterior. If you live in a listed building or in a conservation area you can choose to have a tailor-made option for the rendering which matches other exteriors in the area.

If you decide to insulate from the inside, you can fit rigid boards onto the walls or fix a stud frame. If you do this, you can fill the gap between the frame and the wall with insulation.


How Much Money Can Wall Insulation Save?

According to the Energy Savings Trust if you have installed cavity wall insulation you should make the following savings per year:

  • Detached House - £250
  • Semi - £145
  • Mid Terrace - £95
  • Detached Bungalow - £100
  • Flat - £75

If you install insulation to solid walls you should make a yearly saving of:

  • Detached - £460
  • Semi - £270
  • Mid Terrace - £180
  • Detached Bungalow - £180
  • Flat - £150


Does Wall Insulation Need Planning Permission?

If the outside of your house is going to change dramatically, then you should talk to your local authority planning department because there might be restrictions. The same restrictions may apply if you own a listed building or live in a conservation area. If you don’t need planning permission, you still might need a building warrant. If you’re not sure then speak to someone at the building warrants office at your local council before you start the work.


Will I get a Guarantee?

If you use a company that is registered with the Solid Wall Installation Agency (SWIGA) you will get a 25- year guarantee against defective workmanship, materials or design faults.


What Thickness of Wall Insulation Do I Need?

As is to be expected, the thickness of the wall insulation you will require will depend on the material that you have used. If using rigid insulation boards, it should normally be around 60mm thick, but can go up to around 100mm. When undertaking stud wall insulation, mineral wool fibre is used and requires a thickness of at least 120mm. 

What Are The Benefits of Wall Insulation?

The benefits of installing wall insulation will differ depending on whether you have decided to undergo internal wall insulation or external wall insulation. That being said, there are some benefits that overlap both. 

1. Save Money on Heating Bills 

If you’re looking for ways to save a bit of money, installing wall insulation can mean that less heat escapes from your rooms when you don’t want it to. This, in turn, means that you will rely a lot less on turning your heating on during the cold winter months, and it’ll mean that rooms heat up much quicker when needed too. 

Therefore, the price of your heating bills will fall in line with the lower usage.

2. Reduce Your Carbon Footprint

As you’ll be using less gas and electric energy to heat your home, you’ll also be reducing your carbon footprint, which is an important step to take for the good of the planet. 

3. Protect The Building Fabric

Having wall insulation installed can essentially wrap your home in a protective blanket that prevents heat loss and also protects against weathering, meaning that water ingress is prevented and damage from any extreme weather is vastly reduced. 

4. Eliminate Damp and Condensation

Insulation helps slow down the rate of heat transfer by retaining heat in the walls. Condensation can occur when hot air hits cold walls, but when external walls are warmer due to the insulation, the amount of condensation is reduced. The air quality is also improved, helping you breathe more freely in your home. 

What Kind of Insulation Should I Use For Interior Walls?

The best option for you will depend on your personal circumstances and which would suit your individual home the best. The options are:

  • Rigid Foam Insulation boards: These tend to be thinner than the alternatives and thus take up less space. They do tend to be a bit more expensive than some other options, but for good reason. 
  • Mineral Wools: Knauf and Rockwool are good examples, often available as semi-rigid batts or quilts. 
  • Sheep’s Wool: They provide good levels of breathability and are good options for those interested in the eco benefits. 

What Kind of Insulation Should I Use For Exterior Walls?

  • Fiberglass Insulation: A fairly inexpensive option, fiberglass insulation helps slow down the spread of hot and cold air through walls, but still allows for the air to move in and out of the home. It will need to be replaced eventually, which is something you’ll need to consider if you choose this option.
  • Foam Board Insulation: These rigid panels are either made of polystyrene, polyisocyanurate, or polyurethane. It won’t need to be replaced either once it has been installed. 
3 months ago
487 view(s)