Insulating a single brick wall from inside – 2 methods

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If you live in an older property, your home may lack insulation. Even if you do have insulation, it is likely below the new building regulations standards. These regulations have been updated most recently in June of 2022.

As of this date, all cavity wall construction, should be equipped with 150mm of insulation. This makes modern homes much more energy efficient, meaning far less heat is lost via the walls

However, even if you live in an older property, there are still several ways you can add extra insulation.

If your home is built with a cavity, there are certain options, such as injecting insulation from the outside. This process involves drilling holes in the external skin of the property. Following this, insulation is blown through the holes filling the cavity.

However, not all walls have a cavity. If you are trying to insulate a single brick wall from inside, then you will need a different strategy.

One of the most popular ways to add insulation to in internal wall, is via insulated plasterboard. You also have the option to create an internal stud wall, where insulation is added between the studs. This will take up a little more space. However, it will also create a small cavity, separating your new insulated wall from the external wall.

Insulating a single brick wall from inside

When do you need to insulate a wall from inside?

Cavity wall construction, is by far the most popular construction method used in modern homes. Anything else is generally considered non-standard construction. However, there are still many buildings that have not been built with a cavity.

Things like garages and outbuildings, are often single skin brick walls. If you want to insulate these types of building, you will most likely need to insulate from inside.

Also, cavity walls in properties have only been around since the 1920’s. Prior to this, houses were built using solid wall construction. This consists of a large portion of the UK housing stock.

According to a household energy efficiency report from the government in March of 2021 (which you can see here), there are roughly 8.6 million homes in the UK built with solid walls. Of these properties, only around 9% are insulated, either internally or externally.

According to the same report, even 30% of cavity wall homes have no insulation. This is over 6 million properties that have a cavity, but still don’t have insulation. Because a cavity is present, filling with an injected insulation is the most common option. However, even cavity wall construction could still be insulated from the inside.

Insulating a single skin wall from inside – Method 1

The most common way to insulate your property from inside is with a type of insulated plasterboard. This is fixed to the internal walls and will result in similar U-values to a cavity wall insulation.

Insulated plasterboards consist of a plasterboard face (usually 12.5mm) and a rigid insulation panel fixed to the back. The insulation, will usually rage somewhere between 20-75mm in thickness.

There are two main ways to fix insulated plasterboard. These are:

Dot and dab is a drywall adhesive. To fix boards with this method, the adhesive is added to the wall in dabs, with a solid line of adhesive around the edges of each board. As well as additional adhesive around back boxes, for things like sockets and switches.

The adhesive sets extremely hard, sticking the insulation board to the wall. In addition, the solid lines of adhesive around the edges, prevent cold air from moving behind the boards and escaping into the property.

The second way to attach insulated plasterboard is via timber battens. When using this method, the timber battens are fixed to the wall with plugs and screws. Following this, the boards can be screwed directly to the timber battens.

You should also add a strip of DPM behind the battens. This will give additional protection and avoid moisture passing from the external wall.

Both of these methods will add around 20-25mm behind the insulated plasterboard, so there is very little difference in the finish. However, I would argue that timber battens is the better method, as it gives additional protection from damp, due to the added DPM.

Insulating a single skin wall from inside – Method 2

Your second option for adding insulation internally, is building an internal stud wall. This method will take up a little more space. However, it does also have some benefits.

For this method you would not use an insulated plasterboard. Instead, insulation would be added between the studs in your wall. If you are using 50x75mm studwork, then a similar thickness of insulation could be used.

Your best option for this insulation is a rigid board, such as Kingspan or Celotex. A softer insulation like rockwool, would not be suitable. There is no plaster board on the other side of the wall, so fiberglass insulation would be more prone to slipping down inside the studwork.

When installing the stud wall, you should have a slight gap between the timber and the external wall. Usually something like 20-30mm will be sufficient.

There are a few benefits to this method, which include:

  • A cavity behind the wall allows airflow and can reduce condensation.
  • Damp can’t pass between the walls because there is a gap.
  • You can add an additional vapour barrier with foil backed boards.
  • Your wall can be sat on a strip of DPM to further reduce the risk of damp.

As you can see, most of these benefits are avoiding potential issues from the outside wall. This method is better at avoiding these issues, because it is built completely separate from the external wall.

Any of these solutions are a valid way to do this job. The one you choose will depend on your own skill set.

For me I would generally opt for either battens or internal studwork. However, I am a joiner by trade, so this does lean into my own personal skills.

Conclusion

Insulating a single brick or stone wall from inside is a wise choice, especially if you don’t already have any insulation. Roughly 30% of heat is lost through a property’s walls. Therefore, adding insulation will reduce bills, and help your property to maintain a more balanced, comfortable temperature.

Insulation is also possible from outside. However, this is a far more expensive and difficult process. As a result, insulating from inside is much more popular.