Tag Archives: installation

Why you should have External Wall Insulation on your Cavity Walls

Whether your house should occupy cavity wall insulation (CWI) or external wall insulation (EWI) is an age-old question that still leaves homeowners confused. While it seems obvious that CWI should be installed on cavity walls and EWI on solid walls, there are many benefits to having EWI installed on your cavity walls. Of course, the decision ultimately comes down to what best suits both your budget and your property; however, with CWI’s history of creating issues surrounding damp and mould compared to EWI’s aesthetically pleasing and energy-saving properties, it’s clear why EWI is quickly becoming the favoured choice.

If you’re still torn on which type of insulation would be best for your home, we’ve compiled a little guide on the advantages and disadvantages of both CWI and EWI to aid your decision.

Advantages of Cavity Wall Insulation

If CWI is the only option for you, it does offer some benefits:

  • CWI does not alter the external appearance of your property
  • CWI helps to reduce your energy bills
  • CWI keeps your house warmer in the winter
  • CWI helps to reduce your carbon footprint
  • CWI is very quick and easy to install
  • CWI is cheaper than EWI

Disadvantages of Cavity Wall Insulation

If you are considering CWI, it is important to consider these factors:

  • CWI is at risk of being improperly installed by underqualified installers
  • CWI has been known to trap moisture and cause dampness when poorly installed
  • CWI restricts the amount of insulation that can be installed (dependent upon the size of the cavity), making it less effective than EWI
  • CWI is not suitable for all buildings (i.e. solid wall structures)

Advantages of External Wall Insulation

In contrast, EWI offers many benefits:

  • EWI massively improve the façade of a property due to the decorative topcoat
  • EWI has no restriction as to how much insulation can be installed (you can get up to 200mm+)
  • EWI regulates the thermal comfort of your home, thereby reducing energy costs
  • EWI materials such as Rockwool have soundproofing capabilities as an added advantage
  • EWI has minimal risk of dampness and condensation issues
  • EWI does not cause thermal bridging
  • EWI prolongs the lifespan of the building by protecting its exterior walls
  • EWI increases the value of the property in terms of its energy efficiency and external appearance
  • EWI requires very little maintenance
  • EWI is suitable for virtually any property type

Disadvantages of External Wall Insulation

Though not strictly disadvantages, there are some things to consider before installing EWI:

  • EWI is more expensive than CWI due to the number of materials required and the higher level of skill required to install it, but its long-term benefits make it worthwhile
  • EWI requires skill to install to ensure it is safe and won’t cause problems further down the line, so you need to be careful as to who you hire
  • EWI can be difficult to get planning permission for on older properties as it creates a completely new exterior
  • EWI may need the occasional touch up to ensure the render topcoat remains fresh, but this can be easily completed by giving it a little wash and by using our Silicone Paint

The verdict: Why you should choose External Wall Insulation

If you already have CWI installed and it’s not as effective as you would like it to be, you can certainly have EWI installed as well. By doing this, not only will you achieve two layers of insulation but any thermal bridges within the existing CWI will be negated by the EWI. Together, CWI and EWI will achieve maximum aesthetic and thermal performance.

Nonetheless, the downside is that you can’t have one without the other; trying to install EWI onto an empty cavity wall will achieve very little given that the air within the cavity will be heated up before escaping. Therefore, if you don’t have CWI insulation already, be sure to have that installed first, then consider EWI at a later date.

To conclude, EWI offers an array of benefits to an insulated cavity wall property; it greatly increases the thermal comfort, massively enhances the façade and even prolongs the lifespan of the building, to name a few. If you’re looking for more advice on having EWI installed onto your home, do not hesitate to reach out to our technical team who are available to help every step of the way!

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    Stages of Installing an EWI System

    Stages of installing an EWI system

    You might have heard about external wall insulation (EWI) through the likes of… well, us, or seen it in action whilst it’s being installed on your neighbours’ homes, but what you might not be so familiar with is how it’s installed. Here at EWI Store, we aspire to ensure that all our customers are fully informed about our EWI systems, including how they are installed in certain ways and why, and that what’s this blog is for. Here’s a simple step-by-step guide on how to install an EWI system.

    Wall preparation

    Before any work can begin, the external walls must be prepared. The preparation required varies depending on the condition of the building. In most cases, a simple scrub will do, but sometimes the existing external wall coating needs to be removed entirely. If you are installing EWI onto a smooth surface, then you will need to use our EWI-310 Universal Primer to allow the adhesive to stick to the walls. Alternatively, if the wall surface is uneven, the EWI-260 Levelling Mortar must be used to prepare the wall. To remove any organic growth, consider using a fungicidal wash.

    Starter tracks application

    Once the wall has been prepared, it is time to apply the starter tracks. The types of starter tracks to be applied depend on the EWI system being installed. The correct starter tracks should be applied to the walls above the DPC (damp-proof course). The starter tracks not only allow for the easy installation of insulation to the walls but also protect the surface of the insulation from weather, damp and other damage. The clip-on profile should be attached to aluminium starter tracks to create a neat finish between the starter track and the insulation.

    Insulation application

    After the starter tracks, the basecoat should be applied to the insulation using our modified dot-and-dab method (three dots in the middle and a layer all around the perimeter). For reference, the EWI-220 EPS Basecoat can be used as an adhesive. Use a notched trowel to spread the basecoat evenly across the back of the insulation board. The basecoat should be about 4-5mm thick. When placed on the wall, mechanical fixings should be used to enhance the security of the insulation (6 fixings per square metre of insulation). Allow 2-3 days for the basecoat to set before installing the mechanical fixings.

    Beading and Verge Trims application

    Before adding the basecoat, all beading must be applied. Beading is used to reinforce weak or impact-prone areas within the system, helping to prevent damage and reinforce structural integrity. Each beading has its own special function and area of application:

    • Corner beads: Corner beads are embedded with mesh which sinks into the basecoat. Corner beads reinforce the external corners of the EWI or render-only system.
    • Movement beads: Movement beads are used inside the corners of thermal insulation systems to create a permanent and weather-proof sealant of vertical movement joints.
    • Bellcast beads: Bellcast beads are designed to provide a clean, natural stop to the render just above the DPC. The bellcast bead also propels water from the wall.
    • Render movement beads: Render movement beads should be used where there is an expanse render area. The render movement bead should be applied vertically and is designed to prevent cracking within the render through thermal expansion and compression.

    Basecoat and mesh layer application

    After 2-3 days, another layer of the basecoat should be applied with a notched trowel over the top of the insulation boards at a thickness of 5-6mm. Then, fibreglass mesh is embedded into the basecoat in vertical strips using the flat edge of a notched trowel. Each vertical strip of fibreglass mesh should overlap its neighbouring vertical strip by approximately 10-15cm. At EWI Store, we recommend using fibreglass mesh because it increases the tensile strength of the system and goes an extra step further in preventing cracks and impact damage.

    Render Primer application

    Render primer is classed as an optional step, but to enhance durability and adhesion, we highly recommend applying a render primer to the basecoat. The render primer you use will depend on the render topcoat. For instance, if you’re using our Silicone Silicate render, the Topcoat Render Primer is the most suitable. Alternatively, for our Acrylic render, the Mineral and Acrylic Primer is most ideal. This should be painted on and then left to dry for 12 hours; check out our blog all about our primer range for a deeper insight into render primer and its properties.

    Render application

    Once your final basecoat layer is dry, the final step is to apply the render. When we talk about render, we are referring to our thin-coat render range. The thickness of the render determines how thick the layer should be on the wall. For instance, if you select one of our Silicone Renders with a thickness of 1.5mm, the render should be applied no thicker than 1.5mm from the surface of the wall because, even though our renders are extremely flexible, durable and breathable, this can hinder the EWI system. At EWI Store, our range of advanced silicone renders can be tinted to absolutely any colour, catering to any taste and enhancing the external appearance of your property whilst also improving its thermal comfort.

    And, there you have it! Although this is a very basic installation guide that should be used merely for informative purposes, we hope you found this blog helpful in explaining the stages of installing an EWI system. Every installation is different so, if you have any further questions about installing EWI on your property, do not hesitate to call our technical team who are always happy to assist!