Energy & Buildings 177 (2018) 112–124 Contents lists available at ScienceDirect Energy & Buildings journal homepage: www.elsevier.com/locate/enbuild Evaluating highly insulated walls to withstand biodeterioration: A probabilistic-based methodology Klodian Gradeci a,c,∗ , Umberto Berardi b , Berit Time a , Jochen Köhler c a SINTEF Building and Infrastructure, Trondheim, Norway b Ryerson University, Toronto, Canada c Norwegian University of Science and Technology, Trondheim, Norway a r t i c l e i n f o Article history: Received 4 May 2018 Revised 22 June 2018 Accepted 25 July 2018 Available online 10 August 2018 Keywords: Uncertainty Sensitivity analysis Highly insulated walls Mould Decay Thermal conductivity a b s t r a c t The performance to withstand biodeterioration of highly insulated walls is evaluated by applying a probabilistic-based methodology that accounts for the involved uncertainties and investigates their sig- nificance. Three approaches to representing the outdoor climate are investigated by varying the method and time duration. The temperature-dependent thermal conductivity of the insulation material is mea- sured, and subsequently, a stochastic model is proposed to represent this property. Deficiencies, consid- ering penetration of wind-driven rain, are accounted for and represented by moisture sources in a para- metric way. A sensitivity analysis is performed to identify the influential parameters, and subsequently, simplify the system representation by reducing the number of input variables in order to reduce the computational efforts. The timber ventilated walls show satisfactory performance to withstand biodeteri- oration unless potential deficiencies are considered. The study demonstrates that the probabilistic-based methodology enables a more systematic approach to evaluate wall constructions. It accounts for the in- volved uncertainties, provides a clear association of the microbial growth to its likelihood, and enables the identification and significance of the dominant parameters; hence, it delivers a more comprehensive conclusion regarding the performance of constructions. © 2018 Elsevier B.V. All rights reserved. 1. Introduction Highly insulated walls, which are constructions with an in- creased insulation thickness, have found increasing application over the last few years in order to reduce the heat flow across the wall by increasing their thermal resistance [1,2]. By increasing the thickness of the insulation, the likelihood of moisture-related dam- ages may also increase on the colder side of the insulation [2–5]. When wood-based materials are used as wind barriers, biodeterio- ration presents a serious concern due to the lower growth require- ments [6,7]. Mould and rot decay are biodeterioration phenom- ena that may jeopardise the integrity, functionality and durability of timber construction walls, and violate the comfort and health of the occupants [8–11]. Comprehensive conclusions in terms of moisture performance of highly insulated walls are needed to en- sure their long-term performance, and subsequently to support their wider implementation. ∗ Corresponding author at: SINTEF Building and Infrastructure, Trondheim, Nor- way. E-mail address: klodian.gradeci@sintef.no (K. Gradeci). Highly insulated walls have been previously evaluated for their performance to withstand biodeterioration [2,3,12,13]. The studies are characterised by a deterministic approach; hence, they do not account for the variability of influential parameters. However, the building environment is characterised by a stochastic nature. The performance evaluation of façade constructions is replete with un- certainties. They are related to the outdoor and indoor climate, physical parameters of the materials properties, and the transfer of physical phenomena into numerical equations and models. The performance of wall constructions to withstand biodeterioration will vary because of all uncertainties. In order to develop robust designs by making balanced and sound decisions, a methodology that accounts for the involved uncertainties should be approached. Probabilistic-based methodologies can account for the uncer- tainties, and thus have found increasing application during the last years in the field of building performance simulation, both in the performance evaluation to withstand mould growth [14– 23] or sensitivity analysis [24–27]. A recent literature review may be found in [28]. The results by applying this methodology become more reliable with an accurate representation of the system and performance evaluation to withstand biodeterioration. The former, in case of evaluating highly insulated walls, includes a realistic rep- resentation of the outdoor and indoor climate, incorporates proba- https://doi.org/10.1016/j.enbuild.2018.07.059 0378-7788/© 2018 Elsevier B.V. All rights reserved.