Abstract

Previous studies have shown that the effects of climate change on building structures will increase the mould growth risk of the wood-frame building envelope in many circumstances. This risk can be controlled by wind-driven rain deflection, improving water tightness of the exterior facade, and improving cladding ventilation. However, the effectiveness of these risk mitigation strategies are subject to various uncertainties, such as the uncertainties of wall component properties and micro-climatic conditions. The objective of this paper is to apply stochastic hygrothermal simulation to evaluate the mould growth risk of a brick veneer-clad wood-frame wall with a drainage cavity under historical and future climatic conditions of Ottawa, a Canadian city located in a cold climate zone. An extensive literature review was conducted to quantify the range of stochastic variables including rain deposition factor, rain leakage moisture source, cladding ventilation rate and material properties of brick. The randomised Sobol sequence-based sampling method, one of the Randomized Quasi-Monte Carlo (RQMC) methods, was applied for risk assessment and error estimation. It was found that, under the climatic condition of Ottawa, limiting the amount of wind-driven rain to which walls are subjected is a more robust mitigation measure than improving cladding ventilation in controlling mould growth risk, the improving of water tightness of exterior façade is not as robust as wind-driven rain deflection and cladding ventilation, however, the reduction of rainwater penetration can reduce the mould growth risk at different levels of rain deposition factor and cladding ventilation rate.

Highlights

  • Mould growth is one of the most important mechanisms of degradation that affects the durability performance of wood-frame building envelopes

  • Brambila and Sangiorgio [16] conducted a comprehensive review of the impact of climate change on mould growth in energy-efficient buildings and potential mitigation strategies; they concluded that the control of wind-driven rain and the increase of cladding ventilation were important mitigation strategies to reduce the mould growth risk for wood-frame buildings in the future

  • There was still a lack of studies to evaluate the robustness of different mitigation or design strategies when they are exposed to various uncertainties such as uncertainties evident for material properties and climatic conditions, as well as the influence of other design parameters, in consideration of climate change

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Summary

Introduction

Mould growth is one of the most important mechanisms of degradation that affects the durability performance of wood-frame building envelopes. It is intended that computational efficient stochastic simulation, which is based on Randomized Quasi-Monte Carlo (RQMC) methods, be applied to assess the mould growth risk of a wood-frame building envelope using red matt clay brick as cladding under different climatic realisations, wall orientations, and using different mould growth mitigation strategies. Such strategies could include e.g., control of rain deposition, rain leakage, or the use of cladding ventilation. The risk assessment was based on the historical and future climatic conditions of Ottawa, a Canadian city located in a cold climate zone

Methods
Boundary Conditions and Climatic Realisations
The dimensions listed in building geometry are height: length: width 2 WS
Moisture Source from Rain Leakage
Cladding Ventilation Rate
Literature Review of Sampling Methods
Sampling Methods
Implementation of Sobol Sequence-Based Sampling
Error Estimation and Risk Assessment
The Whole Sample Space
Different Mould Growth Risk Mitigation Strategies
The Influence of Rain Deposition Factor and Cladding Ventilation Rate
The Influence of Rain Leakage Moisture Source
Findings
The Influence of Brick Properties
Full Text
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