Lime Green turns 21

Warmshell External Wall Insulation

Warmshell external insulation is a highly effective EWI (External Wall Insulation) system using wood fibre, or a choice of other boards, that is fitted to the outside of your property – making it significantly warmer and more comfortable to live in.

 The system consists of three main components:

  1. Insulation boards – in a choice of thicknesses and types
  2. Specialist fixings – to suit the specifics of your building
  3. Traditional lime render – in a range of colours and textures

Your internal floor area stays exactly the same, with no disruptive works inside, or redecoration needed afterwards.

And, by choosing the right thickness of wood fibre insulation, you achieve the highest standards of thermal efficiency in a way that suits your home and your budget.

Warmshell external insulation enhances the appearance of your home. You can choose the look and colour you want. And, because our renders are so good at resisting stains and the build-up of mould, your property can will look great for decades to come.


Ideal for many different types of property

You can use Warmshell external insulation for almost any type of property:

  • Brick, masonry, solid wood or timber frame buildings
  • Contemporary or traditional designs
  • New build or retro-fitted installations
  • Domestic or commercial premises
  • Hyper-insulated eco-homes or historic landmarks

To benefit, you just need to be able to get access to the exterior of the entire property and abide by any applicable planning restrictions.

But, of course, if you have a terraced or semi-detached property, live in a conservation area, or simply want to retain the existing look of your house, you can still benefit from our interior Warmshell Internal system.

Achieve the look you want

With the Warmshell external insulation system, you can enhance the appearance of your home – irrespective of whether the look you want is contemporary, rustic or traditional.

One of the benefits of Warmshell is the wide choice of different finishes. Whether you want our lime render for the artisan craftsman, or modern, easy-to-use, silicate thincoat render, we have a many different textures and colours.

But what you won't find is polymer, resin or silicone renders. We think the rubberised, synthetic finishes seen so often don't do justice to beautiful buildings. So all our finishes are made from minerals, not plastics. It means they weather and age like brick or stone, as well as being better for the environment.

And, to help you make your choice, we can always provide sample bags to help decide on the texture, colour and style of render finish you want.


Warmshell isn't just about appearances or sustainability. It has to be safe to install and live with. That's why we have done extensive testing and provide comprehensive advice and certification with our External systems. Talk to our technical team before you start

  • Our technical team can help you assess wind loads on the building, to ensure the right fixings are chosen to resist a 1 in 50 year storm with a large safety margin.
  • U values and condensation risk analysis can be provided free of charge.



Warmshell for new timber frame buildings

Unlike standard methods of timber frame insulation (where the insulation in-fills just between timbers), Warmshell Woodfibre insulation completely encases the property.

This offers a number of significant advantages.

You can expect a Warmshell wall to be warmer, more airtight, and have better acoustics than a standard timber frame design. In practice, this means that a wall as thin as 260 mm will meet Building Regulations standards (0.18 U Value) without the need for additional waste water heat recovery systems or triple glazing. For these reasons, along with its stunning looks and sustainably sourced raw materials, Warmshell using woodfibre is the obvious choice for timber frame, whether you're building your dream home or specifying a large commercial Passivhaus project like Cannock Mill.

Warmshell for historic timber frame buildings

Warmshell is an ideal way to upgrade the thermal performance of existing timber frame buildings.

Breathability is vitally important in historic buildings, as are hygroscopic materials that buffer moisture, protecting delicate structures from decay. So, Warmshell Woodfibre creates a breathable yet airtight envelope around the building – virtually eliminating thermal bridging and drafts, which can seriously compromise energy efficiency. And it can be finished with a beautiful, traditional appearance,  just like at Tyland Barn.

Warmshell for brick or masonry buildings

Warmshell external insulation is a fantastic way to make solid wall brick or masonry buildings significantly warmer and more comfortable to live in. And, you can still keep the beautiful, original look of lime.



Warmshell for solid wood buildings

Warmshell is an ideal way in which to insulate and add weather protection to buildings constructed from cross-laminated timber (CLT) and other solid wood building methods.

These CLT structures are made up of large load-bearing engineered timber panels that are light, stable and very strong. But it is vital that a compatible, breathable insulation is chosen. Warmshell Woodfibre boards are a perfect match for CLT.

Benefit from our installation expertise

Installing our Warmshell external installation system is a straightforward process, but we would urge you to take full advantage of our training and support – or to call on the wide network of system-trained installers.

For builders and plasterers who are interested in learning more about installing Warmshell, we offer regular training days at various locations, so you can become a certified installer.

Training covers important topics, such as:

  • How to make watertight junctions at eaves and window reveals
  • How to fit it around window sills
  • How to choose the right types of fixings beads and trims

Also, there are some significant differences in approach depending on the type of property.


Guideline specifications and detail drawings for Warmshell systems on different external wall backgrounds.

 Timber Guide 

Masonry Guide




See the difference Warmshell External Wall Insultaion can make to the heat loss on different wall types. 







Warmshell systems should be fitted according to the bespoke project specification, but the principles are simple.








Warmshell Warranty


Become a Warmshell partner

With Warmshell, installation is straightforward.

But, to help you on your way, we also offer training, and can put you in touch with a wide network of system-trained installers.

Get In Touch