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How we Specify Buildings for EWI Systems

Buildings come in all shapes and sizes and therefore require us to specify them in various ways. Older buildings, particularly those predating the 1920s, are mostly solid walls, not cavity walls. As such, the U-values are far higher, which results in excessive heat loss and terrible heat retention.

To specify a building is to essentially perform a thorough site survey. However, the focus shifts mainly to the external walls and all the potential areas to address. This can include the DPC, areas around windows, and soffits.

What do we consider when we specify buildings?

  1. Building Age and Design: EWI is particularly beneficial for older properties with solid walls, which typically lack the cavity for insulation that more modern properties have. The design of the building is also important; properties with a large wall surface area relative to their volume, such as detached houses, will benefit the most from EWI.
  2. Wall Construction and Material: Different materials will require different types of insulation and may impact the suitability of a building for EWI. Solid masonry walls, for instance, are often good candidates. Conversely, certain materials may not be suitable for EWI due to moisture or structural issues.
  3. Wall Condition: The wall to be insulated must be in good condition. Any structural issues, cracks, or damp problems should be addressed before installing EWI.
  4. Location and Climate: The effectiveness of EWI can also depend on the climate and location of the building. Buildings in colder regions or areas with high wind and rain exposure might benefit more from EWI.
  5. Building Regulations and Restrictions: Some buildings, such as those in conservation areas or listed buildings, may have restrictions on the changes that can be made to their external appearance. In such cases, internal wall insulation might be a more suitable choice.
  6. Aesthetic Impact: The external appearance of the building will be altered by the installation of EWI. Consideration should be given to how this will impact the building’s aesthetics and whether this is acceptable or desirable.
  7. Future Maintenance Requirements: Consider the future maintenance needs of the building. For example, a building with lots of windows may be more difficult to insulate and maintain.
  8. Economic Viability: Economic factors must also be considered. These can include the cost of installation, the potential energy savings, and the payback period.

Site surveys

During a site survey for external wall insulation, various tests are carried out to ensure that the building is suitable for such a system. The results of these tests guide the design and selection of the insulation system and its components. Here are some of the primary tests performed:

  1. Pull-Out Tests: Also known as anchor pull tests, these are performed to determine the holding power of a fastener in the substrate material. They are used to test the ability of the wall to hold the weight of the insulation system and the render.
  2. Wind Load Tests: These are crucial in understanding how much wind pressure the building’s walls can withstand. This is important for buildings in areas that experience high wind pressure, as the external wall insulation system must be able to resist these forces. It is typically a calculation rather than a physical test.
  3. Moisture Tests: A moisture test assesses the amount of moisture present in the existing wall. High moisture content can cause insulation failure, dampness, and mould growth. These tests may include the use of moisture meters and visual inspections.
  4. U-Value Calculations: The U-value represents the rate of heat transfer through a structure. It’s a measure of how well parts of a building, such as walls, roof, and windows, insulate. The lower the U-value, the better the material is as a heat insulator. Calculating the existing U-value of a building will help determine the required thickness of the insulation to achieve the desired energy efficiency.
  5. Structural Assessment: An overall structural survey of the building is done to ensure it can handle the extra load from the insulation. This can involve checking for cracks, defects, or signs of subsidence.
  6. Thermal Imaging Inspection: This test may be conducted to identify areas of heat loss in a building. The results help in determining the most beneficial areas to insulate.
  7. Render Absorption Test: This test helps in determining the absorption level of the existing render. The result will guide the type and level of pre-treatment needed before the application of the new system.
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