Probabilistic assessment of discomfort risk in buildings

Along with the outdoor climate, building design, materials and construction system determine the thermal behaviour of buildings, the ability to keep indoor comfort conditions and the energy consumption through their lifespan. Buildings must provide comfortable indoor environment which should be reasonably assured regardless of climatic fluctuations. This paper presents a novel methodology for quantifying the hygrothermal discomfort risk of any building design. By means of a numeric model of the building hydrothermal response and stochastic simulation techniques, the expected frequency and duration of discomfort events in each building room and the probability distribution of energy consumption associated to heating and cooling can be estimated. The article presents fundamentals on hygrothermal risk assessment, the numerical simulation models and the developed reliability indexes. In order to illustrate the proposed approach in the context of the design process, the methodology was applied to a prototype of a residential house conventionally built and acclimatized. The materials and construction reflect typical residential housing in the region of study. A bioclimatic variant of the same building is also evaluated. Monte Carlo simulations under stochastic climate conditions allow identifying infrequent but important situations in which the building is unable to meet comfort requirements. Statistical analysis of simulation results is performed and condensed in meaningful reliability indices. By means of these indicators, shortcoming of the architectonic design can be revealed and properly solved. In addition, quantitative comfort reliability indices facilitate the comparison of different thermal building designs on the same basis. The proposed methodology and the developed models can be applied without constraints to any building design under a wide variety of climates.