All retrofit projects need to consider the balance of improving the durability of a structure and maintaining the conservation of a building. However, the two are not mutually exclusive.
The biggest threat to traditional structures is moisture, as the majority of traditional and heritage buildings have solid walls which are notoriously difficult to insulate. This means there is a risk of trapping moisture in the walls which not only affects the longevity of the building, but can be hazardous to the inhabitants’ health.
With that said, Building Regulations state that any work undertaken on traditional buildings regarding energy efficiency “Should not prejudice the character of the host building or increase the risk of long term deterioration of the building fabric or fittings”. According to a report entitled Responsible Retrofit of Traditional Buildings released in 2012, the causes of these problems come as a result of a lack of understanding, incorrect standards and specifications, and poor training by those carrying out the work.
Outside or In
The materials used in wall insulation have a great impact on both the effectiveness of renovation and resulting appearance of the building. Take external insulation for example. This is the most straightforward way to safeguard the health of a building. It takes up no internal floor space, creates less thermal bridging and involves less risk of interstitial condensation. By its very nature, the external façade of the building will be drastically altered. Regardless of the aesthetics of the new exterior, it is highly likely that those wanting to renovate a traditional building will want to retain the exterior appearance. In these instances an internal insulation solution is needed.
Internal insulation comes with its own risks, including damage to interior period features, trapped moisture and rising damp. This can lead to building fabric decay as well as providing optimum breeding conditions for mould and other organisms that can cause respiratory problems for inhabitants.
Given that it is almost impossible to keep walls dry in traditional buildings it is essential that we allow moisture to get in and out and encourage a drying process to ensure long term building health. Actively ‘breathable insulation systems are the solution here being both safer and more robust than non-breathable alternatives. For a successful retrofit, all fabrics must be considered as part of the whole system, recognising the relationship between insulation, airtightness, ventilation, heating systems and usability.
NBT insulation solutions such as Pavadentro and Pavadry are designed specifically for retrofit projects in heritage buildings. These materials are breathable woodfibre systems, and should be utilised once a thorough understanding of the application, the materials and proper training has been acquired.
Striking a balance between conserving a property’s unique features and improving its durability is key.