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Avoidance and diagnosis of problems associated with internal wall insulation

4 October 2017

Internally insulating solid masonry walls can have a hugely positive impact on comfort, but doing so without regard for this relationship can lead to undesirable consequences, including trapped moisture and mould growth. A well-designed specification informed by a good understanding of the building and its context will preclude any unintended consequences.

The avoidance and diagnosis of problems associated with internal wall insulation is addressed in a new publication by Matthew Smith. Internally insulating a solid walled property can lead to a dramatic increase in comfort and energy efficiency. The high density of stone or brick that makes masonry walls so stable and resilient is associated with high thermal conductivity; a significant level of heating is therefore required to provide comfort in these buildings.

A minimal level of insulation can reduce the heat loss through masonry by over 60%, and while quantifying the impact of this on the thermal performance of a whole building requires further research, the potential benefit is obvious: Internal solid wall insulation is among the top three measures for potential fuel savings from domestic buildings.

However, the unintended consequences of insulating internally are poorly understood, and a tendency to regard the installation of internal wall insulation (IWI) as akin to wallpapering, can result in defects that impair structural integrity and occupant health.

The majority of these issues are related to moisture, due to the impact on drying potential of the masonry and the relocation of potential dewpoint (temperature at which condensation occurs for a defined vapour pressure) within the wall. As insulation and airtightness levels increase to maximise energy efficiency, management of water vapour is proving increasingly difficult to achieve. IWI is the most sensitive test-bed for a successful approach.

Author: Matthew Smith, Natural Building Technologies

Source: Journal of Building Survey, Appraisal & Valuation, Volume 6 / Number 1 / Summer 2017, pp. 11-25(15)

Click here to read the paper: Avoidance and diagnosis of problems associated with internal wall insulation