Energy and Buildings 43 (2011) 3391–3399 Contents lists available at SciVerse ScienceDirect Energy and Buildings j ourna l ho me p age: www.elsevier.com/locate/enbuild The inﬂuence of the envelope on the thermal performance of ventilated and occupied houses Cláudia Donald Pereira ∗ , Enedir Ghisi Laboratory of Energy Efﬁciency in Buildings, Department of Civil Engineering, Federal University of Santa Catarina, Florianópolis – SC, Brazil a r t i c l e i n f o Article history: Received 13 June 2011 Accepted 1 September 2011 Keywords: Thermal performance Computer simulation a b s t r a c t The main objective of this article is to investigate the inﬂuence of the thermal properties of the envelope on the thermal performance of occupied and naturally ventilated houses. A naturally ventilated house built in Southern Brazil was modelled and calibrated in the EnergyPlus computer programme. Based on this calibrated model, a reference model for computer simulations was deﬁned, and variations in the materials of the envelope, occupation patterns and ventilation were carried out. Hourly air temperature and relative air humidity were the output data for the thermal zones of each model. By inputting such data in the Analysis Bio computer programme, the percentage of discomfort hours in the models was obtained. Correlations between the percentage of discomfort hours and the equivalent thermal transmittance, thermal capacity and thermal delay values of the components of the envelope were investigated. Such analysis made clear that there is an inﬂuence of the envelope on the thermal performance of the occupied and ventilated house, and that the number of discomfort hours is lower in the models with higher thermal capacity and thermal delay envelope values. It was also observed that thermal capacity was the thermal property with the best correlation to discomfort hours. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The increasing discussions on energy saving and energy efﬁ- ciency have brought attention to matters related to the thermal performance of buildings. Thus, the application of passive condi- tioning strategies is evidenced. Manioglu and Yilmaz [1] consider that the building envelope is the main determinant of its indoor climate, responsible for the heat ﬂows in its interior and, therefore, a determinant factor in its thermal performance. For Ralegaonkar and Gupta [2] the heat gain of a building is directly related to the surface area of its envelope exposed to sunlight. Thus, the choice of construction materials should take into consideration issues such as temperature and humidity. Yilmaz [3] also states that, out of all parameters that affect thermal comfort and energy conservation in buildings, the thermo-physical properties of the envelope are the most important, because the envelope is responsible for separating the outdoor and indoor environment. Despite the fact that several research works have been carried out with regard to the best speciﬁcation of building materials in order to obtain greater environmental comfort, there is a small number of studies that take into consideration the inﬂuence of natural ventilation and occupation by users in the performance of ∗ Corresponding author. Tel.: +55 48 37215184. E-mail addresses: claudia@labeee.ufsc.br (C.D. Pereira), enedir@labeee.ufsc.br (E. Ghisi). the building envelope. This is an issue that must gain attention in the researches concerning tropical or hot climates, where natural ventilation is widely used, especially in dwellings. Many research works [1,3–9] studied the inﬂuence of the enve- lope on the thermal performance of buildings without analysing the inﬂuence of natural ventilation and, therefore, without verifying the possible changes that this factor would cause in the environ- ment. The results obtained in these studies cannot express the behaviour of the real environment, in use. Liping and Hien [10], on the other hand, investigated four ven- tilation strategies (daytime ventilation, night time ventilation, day and night time ventilation, and no ventilation), combined with dif- ferent options of building materials in the envelope (14 options with different thermal conductance and thermal delay values), for naturally ventilated residential buildings in Singapore (hot and humid climate), by using the Thermal Analysis Software (TAS). Some of the main results showed that the properties of the mate- rials of the envelope do not generate signiﬁcant impact on the thermal performance of buildings when they are naturally venti- lated, especially in the cases of daytime ventilation and constant day and night ventilation. The thermal conductance of the enve- lope has considerable inﬂuence on the performance of the building only when the building is not ventilated, and the thermal mass of the envelope is more important in the case of night ventilation. Özdeniz and Hanc ¸ er [11] also took in account natural ven- tilation when comparing thermal performance of 14 types of roofs, checking their suitability for hot climates. Measurements of 0378-7788/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.enbuild.2011.09.001