Innovative and efficient ways to perform numerical simulations are worth investigations to reduce the computational complexity of building models and permit to solve complex problems. This paper proposes a Proper Generalised Decomposition (PGD) model reduction technique for heat and moisture multizone modelling. First, the transient multizone problem is written using PGD formalism and solved in a non-incremental way to assess hygrothermal fields. The computational complexity and accuracy of results of the reduced-order model and the large original model are compared, highlighting that the fields are precisely represented with the PGD resolution. The complexity of the reduced-order model is lower, offering interesting numerical savings, particularly when the number of the building zones increases. The second advantage of the method is for solving parametric problems. Two illustrations are proposed. The first considers a climate and ventilation flow rates parametric multizone problem. The PGD model analyse the behaviour of building zones as a function of these two extra-parameters. For the second, an initial condition and source-term PGD parametric solution is computed. It is then coupled with a wall model to perform whole-building hygrothermal simulation. For both studies, the model represents accurately the hygrothermal fields in the different zones with important computational savings. (C) 2015 Elsevier B.V. All rights reserved.