Abstract
Solid wall buildings account for a quarter of the UK building stock and need to be thermally upgraded to meet national greenhouse gas emission targets. Internal wall insulation (IWI) is often the only option for the retrofit of solid walls, especially when they are of architectural or historical interest. However, IWI can lead to moisture accumulation within the existing wall, affecting the structural integrity of the building and the health of occupants. To avoid these issues, a thorough risk assessment is necessary.This paper presents a method for developing predictive meta-models that can be used for a fast probabilistic moisture risk assessment of IWI, considering both the uncertainty and variability of input variables. First, in a Monte Carlo analysis, the uncertainty and variability of inputs were propagated through hygrothermal simulations. Then, generalised additive models for location, scale and shape (GAMLSS) were used to describe the relationship between inputs and response variables of the Monte Carlo analysis. The key input variables were identified by a global sensitivity analysis - using the elementary effects method - and in model building. Two types of response variable were considered for the models: variables based on percentage values (e.g. maximum relative humidity) and dose-response relationships (e.g. mould index). The paper shows that both risk assessment models had a good predictive power, highlighting the suitability of the developed method for the moisture risk assessment of the internal insulation of solid walls.
Highlights
The impact of greenhouse gas (GHG) emissions on climate change is of global concern; with the Paris Agreement, various countries agreed to reduce GHG emissions in the first legally binding global climate deal
This paper presents a method for developing predictive meta-models that can be used for a fast probabilistic moisture risk assessment of Internal wall insulation (IWI), considering both the uncertainty and variability of input variables
A moisture risk assessment aims at evaluating the likelihood of building failures due to excessive moisture accumulation; it supports decision making and allows designers to choose suitable insulation systems based on information about the risk related to moisture
Summary
The impact of greenhouse gas (GHG) emissions on climate change is of global concern; with the Paris Agreement, various countries agreed to reduce GHG emissions in the first legally binding global climate deal. In the UK, through the Climate Change Act, the Government has committed to the reduction of GHG emissions by at least 80% by 2050 (from 1990 levels). Energy efficiency interventions on solid walls are less cost-effective than other measures commonly installed in the UK; for this reason, properties with solid walls are categorised as ”hard-to-treat” [2]. As of December 2016, only 8% of UK's solid wall dwellings have been insulated [3]; this figure reflects the challenges of solid wall insulation and highlights the potential of this intervention in contributing to the reduction of greenhouse gas emissions pledged by the UK Government. Internal wall insulation is one of the few solutions for the energy efficiency of solid walls, especially if the façade is of special architectural or historic interest. A moisture risk assessment aims at evaluating the likelihood of building failures due to excessive moisture accumulation; it supports decision making and allows designers to choose suitable insulation systems based on information about the risk related to moisture
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