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Do You Need a Secondary Mesh Layer?

Last modified: 28.02.2024
Close-up of a worker applying mesh-embedded basecoat using a stainless steel trowel on external wall insulation. The visible EWI Pro branding on the mesh indicates use of a certified and reliable system, available from EWI Store for effective thermal performance and surface reinforcement.

When considering enhancements to External Wall Insulation (EWI) systems, the question of whether to incorporate a secondary mesh layer often arises. This additional layer plays a critical role in reinforcing the insulation system, offering improved mechanical strength, durability, and crack resistance. A primary layer of fibreglass mesh is essential in all EWI and render systems. However, we recommend a secondary mesh layer. Whilst it may seem superfluous, it does allow access to a new level of funding through EWI Pro's innovative DSP system.

The role of fibreglass mesh in External Wall Insulation (EWI) systems is multifaceted and critical for enhancing the overall performance and durability of the insulation. Fibreglass mesh is embedded within the basecoat layer of the EWI system, serving several key functions:

  1. Reinforcement: It provides structural reinforcement to the insulation layer, significantly reducing the risk of cracking and deformation under mechanical stress or thermal expansion and contraction. This reinforcement is crucial in maintaining the integrity and effectiveness of the insulation over time.
  2. Impact Resistance: By distributing stresses more evenly across the surface, fibreglass mesh increases the system's resistance to physical impacts, such as those caused by wind-driven debris or accidental collisions. This is particularly important in protecting the insulation's surface from damage that could compromise its thermal performance.
  3. Compatibility and Versatility: Fibreglass mesh is compatible with various types of insulation materials and finishes, making it a versatile choice for different architectural styles and building requirements. It can be used with a range of basecoat and render products, allowing for flexibility in design and application.
  4. Prevention of Algal and Fungal Growth: Some fibreglass meshes are treated with fungicidal and algaecidal coatings to prevent the growth of algae and fungi on the facade, contributing to the longevity and aesthetic appeal of the building's exterior.
  5. Ease of Installation: Despite its strength and durability, fibreglass mesh is lightweight and easy to cut and apply, facilitating a swift and efficient installation process. This efficiency is essential in minimising construction time and labour costs.

The types of fibreglass mesh used in External Wall Insulation (EWI) systems vary in terms of their Grams per Square Meter (GSM), which directly impacts their strength, durability, and application suitability.

  1. Standard Fibreglass Mesh: This mesh typically has a GSM ranging from 110 to 160. It's designed for use in standard EWI applications where a balance between strength and flexibility is required. Suitable for residential buildings with minimal exposure to mechanical stress.
  2. High-Tensile Fibreglass Mesh: With a GSM value ranging from 165 to 200, this type of mesh offers enhanced tensile strength and is ideal for areas subjected to higher mechanical stresses or where a higher level of impact resistance is needed, such as commercial buildings or lower floors of residential buildings in urban areas.
  3. Panzer Mesh: Panzer Mesh is a high-density fibreglass mesh with a GSM of over 300. It provides exceptional durability and impact resistance, making it suitable for high-risk areas, including schools, hospitals, and buildings in harsh environmental conditions.

EWI systems are crucial for enhancing a building's thermal performance, but the DuraShield Pro system takes this a step further. At its core, the DSP system is an advanced ETICS (External Thermal Insulation Composite Systems) solution which extends the lifespan of buildings significantly. This system is a product of meticulous engineering, aimed at providing an unparalleled combination of thermal efficiency, impact resistance, and aesthetic appeal.

The DSP system's distinguishing feature is its enhanced impact resistance, primarily attributed to the integration of a secondary mesh layer known as the Panzer mesh. This addition not only triples the system's durability compared to conventional EWI systems but also significantly improves its flexibility and resilience to mechanical stresses. The Panzer mesh, with its superior strength, elevates the DSP system's ability to withstand environmental and accidental impacts, thereby safeguarding the building's exterior facade over an extended period. External wall insulation is seldom simple; however, the ‘why’ for DuraShield Pro could not be simpler. Regular warranties range from 10-25 years; DSP offers a 60-year warranty. An EWI system has reasonable impact resistance; on the other hand, DSP triples that value. Crucially, the funding support for a DSP system is uplifted to 45% of the total value of the project. We can access this uplift due to the acquisition of an Ofgem Innovation Link accreditation. The performance enhancements stem from significant installation and manufacturing alterations.

The DSP system represents a leap in EWI technology, incorporating significant installation and manufacturing enhancements. One such advancement is the modification of the EWI-225 Premium Basecoat's chemical composition. The refinement increases the system's durability without compromising its flexibility and adhesive properties. This meticulous enhancement, coupled with the secondary Panzer mesh layer, underscores EWI Pro's commitment to delivering superior quality and performance.

EWI Pro has rigorously tested its systems to ensure they meet the highest standards of durability and impact resistance, utilising a comprehensive testing procedure developed in partnership with the Technical and Test Institute for Construction Prague. This procedure aims to provide transparent and comprehensive insight into the impact resistance capabilities of their systems, extending beyond the standard testing outlined in their BBA certification (Agrément 18/5503).

  • Enhanced Tolerance at Higher Joules: Testing of the improved EWI-225 Premium Basecoat recipe with a single layer of 160g fibreglass mesh demonstrated an improved tolerance of impact resistance at both 15 and 20 Joules. This is a significant enhancement over the standard testing reported at 3 and 10 Joules in the BBA certification. The system showed no surface cracking at these higher impact levels.
  • Minimal Impact on Underlying Insulation: The new testing methodology revealed no or minimal impact on the underlying insulation behind the render system at these higher joules, a discovery not possible with previous testing methods. This indicates that the system effectively dissipates impact energy, protecting the insulation layer.
  • Superior Surface Tension With Double Mesh Application: When testing the EWI-220 Basecoat with a double mesh application, the system withstood surface tension impacts up to 40 Joules – four times stronger than the upper limit reported in the BBA certification.
  • Remarkable Performance with Mineral Wool and High-Density Mesh: This setup withstood an astonishing 80 Joules of surface impact without external blemishes on the render – eight times stronger than standard results. Even at 100 Joules of impact, the maximum crack observed externally was only 0.35mm.
  • Impressive Internal Crack Resistance: Despite the high impact levels, internal cracks on top of the insulation were minor and only became vividly apparent at 80 Joules of impact. This indicates that the system not only protects the exterior façade but also maintains the integrity of the insulation layer under extreme conditions.
  • No Spalling of Grains at High Impact Points: With the improved silicone render's elasticity, no spalling of grains at any of the impact points, even at 100 Joules.

The DSP system is particularly beneficial for government-funded and social housing projects, offering an extended lifespan, enhanced durability, reduced maintenance costs, and improved safety and security. These advantages are vital for ensuring the long-term viability and integrity of housing structures, providing residents with peace of mind and confidence in their homes' quality and stability.