Here at EWI Store, we provide customers with a whole-system approach to external wall insulation. We sell all the products required for the job, and we can put you in touch with any of our approved installers in your area.

However, there are instances where customers want to use our systems but they wish to swap out the insulation board with an alternative insulation board to the ones that we offer (Mineral Wool, EPS and Wood Fibre). It could be that the customer would prefer to use a 100% natural insulation material such as cork insulation boards, or they would like to use Kingspan K5 insulation boards because a thinner amount is required to achieve the same thermal performance.

We wouldn’t generally advise that this is the best approach, because our external wall insulation systems are designed so that the products are technically engineered to work in conjunction with each other. By using an alternative insulation board, you may be compromising the quality and strength of the system.

However, this isn’t to say that it can’t be done. You can use EWI Pro external wall insulation systems with other insulation boards. Nevertheless, there are a few things that we would recommend you do to ensure that the system is totally secure.

Using EWI Pro adhesives with alternative insulation boards

Whilst it is possible to use other insulation boards, we suggest that you do not stray too far away by using other adhesive materials. We would recommend that you stick to EWI Pro materials for the rest of the installation. By doing this you’ll be better off in the long run because the rest of the materials in the system will work properly in conjunction with each other (as they are designed to) and it will minimise any risks or problems further down the line.

When using an alternative insulation board, we encourage the use of the EWI-225 Premium Adhesive to secure the insulation boards to the substrate. The type of adhesive that you use does usually depend upon how heavy the insulation material is. However, it’s better to be safe than sorry – so in order to completely ensure that the alternative insulation boards will adhere to the substrate properly, it is imperative that you use our extra strong adhesive.

The 225 Premium Adhesive has been designed with EWI Pro insulation systems in mind, most especially Rockwool insulation boards which tend to be a bit more heavy than EPS. The Premium Adhesive is extra strong, and contains strands of fiberglass embedded into the material. This basically means that the tensile strength of the adhesive is overall much higher than other alternative adhesives. So you can be confident that it will bond to the alternative type of insulation board, and ensure that it is firmly secured to the substrate.

The EWI Pro adhesives are also highly breathable. So when installed properly, the EWI-225 will support the system against the dangers of water ingress.

As well as this, by using the EWI-225 any EWI Pro renders applied as a top coat will bond to the adhesive correctly. This is again because our renders have been designed be applied on top of EWI Pro materials. Applying our renders to any other type of adhesive may affect the success of their application and their longevity.

Using EWI Pro Mechanical Fixings with other insulation boards

Another suggestion that we would make when you are using an alternative insulation material is the type of mechanical fixings that you use.

Our Mineral Wool boards are much heavier than EPS, so we advise that installers use metal fixings because these are much stronger than plastic.

For alternative insulation materials, we therefore recommend that you follow the same guidelines and use metal fixings for added strength and security. Metal fixings also require the application of EPS thermo dowel caps to the heads of the fixings to prevent thermal bridging. By following these guidelines, you’ll be giving your external wall insulation system an added layer of security.

Using EWI Pro Silicone Render with other insulation boards

The final step in the system is choosing which render would suit the insulation system best. We would advocate our silicone render when using alternative insulation boards. This is because silicone render is our premium render, with unrivalled breathability and strength. Basically, by using a silicone render you are adding an entirely waterproof and vapour permeable layer to the exterior of the EWI system.

Water ingress is the worst possible occurrence for an external wall insulation system. If your insulation boards lack breathability, then any water vapour collecting within the system can compromise how well it functions (its ability to insulate), and it can also mean that over time the system becomes improperly secured to the substrate. If you were to use a non-breathable render, it would trap any moisture within the system and could compromise its structural integrity. Using breathable materials such as our silicone render is therefore your safest bet and will reinforce the system’s ability to breathe and function.

If you have any further questions, we are always on hand to give technical support and advice so just give us a call and we would be happy to help! Alternatively, if you are looking for an external wall insulation installer then we have a whole list of approved installers who we can put you in touch with!