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What is WUFI and Why is it Important for EWI?

In the dynamic world of building science, understanding how materials interact with environmental factors is paramount. This is where WUFI (Wärme Und Feuchte Instationär), a cutting-edge software tool, comes into play, particularly when considering External Wall Insulation (EWI). Careful planning and modelling for EWI are crucial for many reasons. One of the major issues that plague retrofits and new builds is thermal bridging. Certain modelling software will be able to display where these thermal bridges occur, allowing the system designer to eliminate them. WUFI works in a slightly different way, which we discuss in this blog.

What is WUFI?

WUFI, a German acronym translating to “Transient Heat and Moisture,” is a powerful software developed by the Fraunhofer Institute for Building Physics. It’s designed to simulate heat and moisture transfer in multi-layer building components. In simpler terms, WUFI allows architects, engineers, and builders to predict how different materials will behave under various climatic conditions over time.

Core capabilities of WUFI
  1. Hygrothermal Simulation: At its core, WUFI is a hygrothermal simulation tool. “Hygrothermal” refers to the movement of heat and moisture through building materials. This dual aspect is crucial because heat and moisture transfer often interplay, impacting the building’s overall performance.
  2. Dynamic Analysis: Unlike traditional static analysis tools, WUFI uses dynamic modelling to simulate real-world conditions. It can account for varying weather patterns, temperature fluctuations, and humidity changes over time, offering a more realistic view of how materials will perform.
  3. Multi-layer Component Analysis: WUFI excels in analysing multi-layer construction components, such as walls with EWI. It can assess each layer’s response to environmental conditions, providing a comprehensive view of the entire system’s performance.
Applications in building science
  1. Material Selection: By simulating different materials under varied conditions, WUFI helps in selecting the most suitable materials for specific climatic conditions, enhancing the effectiveness and durability of EWI.
  2. Design Optimisation: WUFI aids architects and engineers in optimising the design of EWI systems. For instance, it can determine the optimal thickness of insulation needed for maximum energy efficiency.
  3. Research and Development: WUFI is extensively used in R&D to test new building materials and methods. Its detailed simulations can predict how innovations in EWI will perform, speeding up the development of more advanced solutions.
The science behind WUFI

WUFI is grounded in the principles of building physics. It uses advanced algorithms to simulate heat and moisture transfer based on physical laws. The software incorporates:

  1. Weather Data: It utilises actual meteorological data, including temperature, humidity, rainfall, and solar radiation, to create realistic environmental conditions for simulation.
  2. Material Properties: WUFI contains an extensive database of material properties, including permeability, thermal conductivity, and specific heat capacity. Users can also input custom material data for specific projects.
  3. User Interface and Outputs: The software is designed with a user-friendly interface, providing detailed outputs like moisture content, temperature profiles, and risk assessments for mould growth or structural damage.


External Wall Insulation is a critical element in modern construction, especially for energy efficiency and building longevity. EWI systems involve applying insulation material to the exterior of buildings, which can drastically reduce heat loss. However, the interaction between the insulation, the external environment, and the building itself can be complex. This is where WUFI’s significance becomes evident.

Enhanced understanding of moisture dynamics
  1. Accurate Moisture Behaviour Prediction: WUFI’s ability to accurately predict how moisture behaves within EWI systems is paramount. It simulates how moisture interacts with various materials, considering factors like absorption, diffusion, and drying capacity. This is critical in preventing moisture-related issues such as dampness, which can compromise the integrity of the insulation.
  2. Long-term Moisture Risk Assessment: WUFI enables long-term predictions about moisture risk, helping to identify potential problems that could arise years after installation. This foresight is invaluable in ensuring the longevity and effectiveness of EWI systems.
Optimisation of thermal performance
  1. Energy Efficiency Assessment: WUFI’s simulations help in determining how different insulation materials and thicknesses will perform in terms of energy efficiency. This assists in creating EWI systems that effectively reduce heating and cooling costs.
  2. Climate-Specific Solutions: WUFI takes into account local climate data, ensuring that the EWI system is optimised for the specific weather conditions it will face. This means that a building in a rainy maritime climate and one in a dry continental climate can have EWI systems tailored to their unique environmental challenges.
Proactive risk mitigation
  1. Structural Durability Analysis: WUFI helps in assessing the impact of EWI on the structural durability of a building. By understanding how insulation interacts with the building’s fabric, it’s possible to prevent potential damage caused by factors like freeze-thaw cycles and thermal expansion.
  2. Mould and Condensation Prevention: WUFI’s simulations are crucial in identifying areas at risk of mould growth and condensation within EWI systems. By predicting these risks, preventative measures can be implemented, ensuring a healthier living environment.
Regulatory compliance and sustainability
  1. Meeting Building Regulations: With increasing focus on energy efficiency in building codes, WUFI helps ensure that EWI systems comply with these evolving standards. This is essential not only for regulatory approval but also for meeting sustainability goals.
  2. Lifecycle Analysis: WUFI enables a comprehensive lifecycle analysis of EWI systems, considering long-term performance and environmental impact. This aligns with sustainable building practices, ensuring that EWI systems contribute positively to the building’s overall environmental footprint.
Facilitating innovation in insulation materials
  1. Testing New Materials and Techniques: WUFI allows for the testing of new insulation materials and methods in a virtual environment. This capability is crucial for innovation, allowing researchers and manufacturers to explore and validate new approaches before physical implementation.
  2. Customisation and Experimentation: With WUFI, professionals can experiment with custom configurations and materials, pushing the boundaries of what’s possible in EWI technology. This opens up new possibilities for energy efficiency and building design.
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