NZEB Modular Prefabricated Building System

Lightweight prefabricated construction systems present some challenges to comply with building thermal regulation, namely in summer period, because of their low thermal mass. Modular prefabricated building system has special connection elements that need detailed calculation to allow the assessment of building thermal performance. This article presents the main findings of the study of an innovative modular prefabricated building system to fulfill the NZEB requirements, for detached single-family house, located in different climate zones in Portugal. The thermal performance assessment focuses on the quantification of the thermal transmission coefficient of the panel and the linear thermal bridge coefficients of the innovative connections that result in an automation of the construction process. This assessment was performed with finite element calculation method. The evaluation of the energy performance of the single-family house was done using seasonal method. The thermal transmittance of the innovative system for wall (U_d.S = 0.22 W/(m² K)), roof and floor is approximately 25–56% lower than national minimum requirements (U from 0.30 W/(m² K) to 0.50 W/(m² K)). The linear thermal transmission coefficient for the different panels connections is about 23–92% lower than the reference values. Despite this high thermal insulation of the construction system, to fulfill the NZEB requirements, windows with high solar shading and free cooling are required, to overcome the restriction imposed by the low thermal inertia of this construction. This study of the prefabricated modular construction solution, with high thermal insulation and an innovative system for connecting the panels, reflects that this construction solution, despite being of low thermal inertia, allows the design of NZEB single-family houses, regardless of the climate zone in which it is implemented. However, it presents a better thermal performance for a south orientation of the main façade.