The Importance of Breathable Internal Wall Insulation

By Jamie Orr
Date 19/04/2022
the importance of breathable internal wall insulation

What do you want from internal wall insulation? Thermal efficiency is no doubt top of the list. But one thing that’s often overlooked is how breathable the solution is. In this post, we’ll discuss why breathable insulation matters for your internal walls.

Why breathability matters

To understand why breathable internal wall insulation matters, it’s worth looking at the walls they’re insulating. Walls can be either permeable or impermeable, which is crucial in determining the type of insulation used.

Permeable walls allow moisture to pass through (or permeate) them, while impermeable walls do not. To work properly, that permeable wall needs to be breathable on both sides. Otherwise, moisture will get in one way and won’t come out the other.

If you add non-breathable insulation on the internal side of a wall, you’ll basically be trapping moisture within the wall. That leads to damp, which has the following knock-on effects:

  • Structural damage – If it spreads to timber, damp can cause rot.
  • Mould – Damp provides the perfect conditions for mould development, which increases the risk of respiratory problems.
  • Unsightly – Let’s face it, nobody wants damp or mould to be part of their design scheme.

Isn’t all internal wall insulation breathable?

In short, no. Some of the most well-known materials used for internal wall insulation are not breathable. That includes polystyrene and foam-based products, which don’t let moisture through their structure.

What’s even more concerning is that these materials are the most commonly used for solid wall insulation (SWI), according to a report for the Department of Business, Energy and Industrial Strategy. While “some experts insist that only breathable materials should be used” for SWI, “the most common methods of carrying out SWI still use impermeable materials”.

3 types of internal wall insulation

The government report outlines two options when it comes to breathable internal wall insulation – namely, glass wool and wood fibre. According to the report, glass wool (or fibreglass) is less commonly used for retrofit wall insulation because it’s “liable to slumping, creating cold bridges.”

On the other hand, wood fibre offers inadequate insulation values compared to other materials. It also needs to be used with three coats of lime plaster, which makes it both time consuming and costly to install.

Another downside for both of these options is their size. With the thickness of the insulation material and the additional coats of plaster, both can eat away at the size of a room.

Thankfully, there is an alternative – a sprayed cork coating. SprayCork is breathable to let moisture through while being impermeable to liquids on the surface, making it uniquely suited to the requirements of permeable walls.

In terms of application, the breathable internal wall insulation is spray applied in two 3mm coats. That’s finished with a 2mm skim of plaster, meaning the entire solution is just 8mm thick.

Get a quote from an approved applicator

If you’re looking for internal wall insulation that’s breathable and thermally efficient without compromising on space, SprayCork ticks every box. Best of all, it’s available exclusively to our Network of Approved Applicators, who have all been fully trained to achieve the highest standards.

To get a quote from your local applicator or find out more about SprayCork, simply contact the CorkSol team on [email protected] or 01484 442420.

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