External vs Internal Wall Insulation – How to Decide

By Jamie Orr
Date 12/08/2022
external vs internal wall insulation – how to decide

Photo credit: WBS Ltd


Insulating your walls is a great idea if you want to make your home more energy efficient. But there isn’t just one type of insulation. One of the biggest decisions you’ll have to make is whether you want internal or external wall insulation.

To make things easier, this post goes through some of the key factors to consider when making your decision…


The first factor is space. All too often, this is the deciding factor between external and internal wall insulation. Why? Because traditional insulation like panels or blocks are pretty bulky. Installing them internally can reduce the size of your space significantly, leading people to opt for their external counterpart instead.

But it doesn’t have to be that way. Modern products like SprayCork allow you to insulate from the inside with a coating that’s just 8mm thick.


Adding insulation will naturally alter a building’s internal or external appearance. Inside, you’ll typically get a fresh plaster finish that needs to be decorated. Outside, you can expect a rendered finish on top of insulation boards – or one that’s naturally insulative itself.

If your house is already rendered, opting for external insulation can kill two birds with one stone, so to speak. As well as upgrading your thermal efficiency, you can rejuvenate the appearance of your walls.

On the other hand, buildings that are listed or situated in conservation areas might actually be prohibited from applying external wall insulation. If that’s the case, internal wall insulation might be a better solution – though you should always check with your local authorities or conservation officer first.


Cost is an unavoidable factor for practically all home improvements. When it comes to wall insulation, internal jobs are typically cheaper. That’s because there’s no need for scaffolding or alternative platforms to complete the job. Materials for external insulation may also be more expensive given that they need to be weatherproof for outdoor use.

Whichever route you go down, the best advice here is to invest in quality. While cost will naturally play a part, it shouldn’t be a standalone factor in your choice of insulation. Rather than buying cheap and buying twice, it’s better to let good insulation pay for itself over time by reducing your energy bills.


Finally, performance – which type of insulation is more efficient? In most cases, the answer is external wall insulation. That’s because it provides a complete, uninterrupted barrier on the outside of your walls.

On the other hand, internal wall insulation can only be applied from the floor to the ceiling, before starting again from the floor on the next level up. As a result, it typically has cold bridges between floors where some heat can escape.

External vs internal wall insulation – the verdict

When deciding between internal and external wall insulation, it comes down to what suits your requirements. Externally, you’ll get a bit better performance with a fresh look for your walls. You can also sidestep any spatial issues if you’re using traditional panels.

That said, internal wall insulation is still incredibly effective at a slightly lower cost – and is more likely to be permitted for listed/conservation buildings. With a modern, sprayed coating, you can also sidestep the bulk of internal panels.

Whichever side you land on, CorkSol has a thermally efficient coating for your walls. Our sprayed cork solution can be used as external insulation or an internal coating reduce your heating bills by up to 15%. To find out more, give us a call on 01484 442420 or email [email protected].

Share this post

Latest Posts





Subscribe to our newsletter
Sign up for our newsletter to learn more about CorkSol.

"*" indicates required fields

This field is for validation purposes and should be left unchanged.

user linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram