Specifications are essential as they provide an incredibly detailed manual for installing EWI systems. Every system can be different; we provide in-depth, site-specific specifications, with considerations for all potential problems. This includes the assessment of thermal bridging, ventilation, air tightness, pressure, heat, and moisture conditions. Each of these facets works in harmony to deliver a system that will remain effective for up to 25 years, increase energy efficiency, and improve overall thermal comfort.


Whilst we do say our scope is extensive, it is crucial to clarify just how extensive it can be! Our highly experienced and skilled team can perform many forms of substrate testing. Information gathered from pull-out, wind-load, moisture content, porosity testing, thermal imaging, and survey details are fed back to the technical office. From this, our experts produce any required specification, no matter how large the property is or how difficult the circumstances are. We specify anything from a small garden shed used as a home office to multi-storey residential properties suffering from health-threatening damp. Crucially, our team will guide you through the process; a specification can seem daunting and complicated, but our friendly experts will break everything down and answer any question you can think of. Best of all? Our specification offering is free of charge!



U-values for external wall insulation (EWI) are critical measures used in building physics to quantify the rate of heat transfer through the external walls of a building. These values, expressed in watts per square metre per degree Kelvin (W/m²K), indicate the thermal conductivity of the wall assembly with the insulation in place. A lower U-value signifies better insulation performance and greater energy efficiency, as it means less heat is lost through the walls. EWI systems are designed to reduce these U-values significantly, enhancing the building’s overall thermal efficiency. This reduction in heat transfer improves energy savings, contributes to a more comfortable indoor climate, and reduces carbon emissions. U-values are essential for architects, engineers, and builders in designing, retrofitting, and assessing the energy performance of buildings, ensuring compliance with energy regulations and sustainability goals.


WUFI test
WUFI is an acronym for Wärme Und Feuchte Instationär, which translates to ‘Heat and Moisture Transient’, and is a cutting-edge software tool designed for simulating the transient coupled heat and moisture transfer in multi-layer building components. Originating in Germany, WUFI employs sophisticated algorithms to predict the heat and moisture conditions in building components under natural climate conditions. Its primary application lies in improving buildings’ energy efficiency and durability by helping architects, engineers, and builders understand how different materials and designs respond to various environmental conditions over time. The software is invaluable for assessing risks like condensation, mould growth, and structural damage, thereby informing better design and construction practices.

Armed with this knowledge, our fabulous Specifications team can produce documentation to support our customers’ installs well in advance.


Psi Values

Psi values, in the context of external wall insulation, refer to the measure of thermal bridging at specific points or junctions in a building’s envelope. These values represent the linear thermal transmittance, indicating how much heat is lost through the junctions or interfaces between building elements, such as where a wall meets a window or floor. Expressed in watts per metre Kelvin (W/mK), lower psi values indicate better insulation and less thermal bridging, leading to improved energy efficiency. Accurately calculating and minimising psi values is crucial in building design, as it enhances overall thermal performance, reduces heat loss, and contributes to achieving better energy ratings and compliance with building regulations.

Wind-load Testing

Wind-load tests are designed to simulate the impact of wind pressure on a structure. These tests determine how much wind force a building or a specific part of it can withstand before it fails or becomes unsafe. Wind-load tests can reveal potential weak points in a building’s design. Therefore, engineers can make necessary modifications to ensure safety and reliability. Concerning EWI and render, such tests help to confirm that the installation will resist the high wind pressures that some buildings, especially high-rise structures, are subjected to. By doing so, we can ensure that the insulation or render won’t be dislodged or damaged by heavy winds.

INCA sets out specific guidance for wind loading. In terms of factors that affect wind loading and the impact it has, INCA states the following:

“The forces created by the wind on a building are very dependent upon the wind direction and the orientation of the building to the wind. Designers should therefore be mindful of the prevailing wind direction for a given site and how they might optimise the building performance by orientating the building accordingly.
High winds are often associated with high buildings, whereas the reality is high wind loads can also be experienced in low-rise construction. Tall buildings interrupt airflow at a high level, which accelerates as it is forced down towards the ground. This has the effect of increased loads at both higher altitudes and ground levels. Similarly, where buildings are very close together, the venturi effect (as the wind is compressed) results in very high localised wind speeds and associated high pressures. This effect is known as funnelling and the potential for this effect to occur should be carefully considered on each site.” (INCA, Wind Load Design Considerations for EWI Systems)

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