On the cost reduction of a nearly zero energy multifamily house in Italy: Technical and economic assessment

Two important issues concerning NZEB development are: from one side to guarantee specific heating-cooling balance for each climatic condition, taking into account thermal comfort and indoor environmental quality, and from the other side to enhance the reduction of construction and management costs, ensuring the fulfillment of NZEBs standard requirements. In this paper these two aspects have been analyzed. Numerical analyses under transient thermal conditions demonstrated that passive design (night ventilation and shadings) allow to minimize the overheating risk in summer season and consequently to avoid the installation of an active cooling system: up to 65% average cooling demand reduction can be obtained; 1.5 air change rate of night ventilation allowed to reduce the overeating risks to 16 hours only. Furthermore, the development of low-cost technical solutions in the construction phase guarantees up to 25% reduction of investment costs and high final savings, considering operational costs over the entire building life cycle (50 years). The Net Present Value of the four scenarios range from 63 €/m 2 to 140 €/m 2