nZEB: bridging the gap between design forecast and actual performance data

The nZEB objectives have raised the standard of building performance and changed the way in which buildings are designed and used. Although energy dynamic simulation tools are potentially the most suitable way for accurately evaluating and forecasting the thermal performance, they need several data inputs and user's knowledge that can affect the reliability of the results. It is precisely these two aspects that proved to be particularly critical, since the reliability of the ICT calculation tools has been widely proven in recent time. However, in order to foster credibility in sustainable architecture, bridging the gap between predicted and measured performance is pivotal to boost the building market towards energy efficiency and provide reliable data to inhabitant, investors and policy maker. The present research aims to identify and quantify the main factors that affect the energy performance gap through a detailed energy analysis carried out on a case study, which can be considered one of the first nearly zero energy residential complex built in Italy. Based on the analysis, the study identifies the main causes of the deviation between the calculated and measured data and demonstrates how it is possible to achieve very reliable models and, therefore, real buildings. Although the procedure traces a classic model calibration scheme, actually it consists of a verification of possible downstream errors mainly due to human factors, such as the provision of incorrect technical data or inappropriate operation. Some observations on the technical, management and regulatory gaps that may generate these errors are reported at the end of the study, together with practical suggestions that can provide effective solutions

Validation of dynamic hygrothermal simulation models for historical buildings: State of the art, research challenges and recommendations

The proper simulation of the hygrothermal behaviour of historical buildings is a challenging task with several implications regarding the evaluation of indoor thermal comfort and the suitability of retrofit strategies that comply with the conservation of cultural heritage. An inaccurate simulation may lead to inadequate conclusions, which could result in inappropriate and dangerous actions for the preservation of the heritage buildings. Then calibration and validation of hygrothermal simulation models are essential steps to achieve more accurate and reliable results. Now, although some agencies have developed guidelines and methodologies to carry out the validation of building performance models, all of them are based on energy consumption only. However, since in some buildings the energy consumption data are not always available especially when no operating heating, ventilation and air conditioning system is installed, which is the case of many historical buildings, the microclimatic parameters are usually adopted in the validation process. In this case, neither protocols nor specific parameters have been officially recognised to perform the model validation. The present work reviewed the main approaches used by researchers for building performance model validation with special reference to historical buildings based on microclimatic parameters, highlighting the main advantages and drawbacks of the different methods reviewed. Finally, recommendations to properly carry out the model validation based on microclimatic parameters have been provided. The collected information may be useful to different subjects (e.g. designers, energy auditors, researchers, conservators, buildings’ owners and policy makers) and can drive suitable and reliable retrofit and maintenance interventions

Wooden Biomass Cogeneration Coupled with Groundwater Heat Pumps and Photovoltaic Systems: the Case Study of a New Low Carbon District in Northern Italy

In the framework of the de-carbonization of the building sector, which can be achieved also by new generation district thermal plants and renewable sources integration, the case of a new nearly zero energy district is presented. After the evaluation of the energy needs, an innovative district thermal plant was designed to be integrated with groundwater heat pumps (GWHP) and solar photovoltaic (PV) systems. The core is a biomass boiler coupled with a small combined heat and power (CHP) unit with a twin-screw steam expander (TSSE). Heat produced by the CHP satisfies a consistent fraction of space heating and domestic hot water (DHW) needs during winter season. GWHPs coupled with PV satisfy remaining thermal needs in winter and the entire thermal needs in mid-seasons and in summer period. The outcomes demonstrate the benefits of the combination of a biomass CHP with GWHPs and PV with a significant increase of renewable energy share with respect to conventional applications in nearly zero energy districts

Dynamic thermal and hygrometric simulation of historical buildings: Critical factors and possible solutions

Building dynamic simulation tools, traditionally used to study the hygrothermal performance of new buildings during the preliminary design steps, have been recently adopted also in historical buildings, as a tool to investigate possible strategies for their conservation and the suitability of energy retrofit scenarios, according to the boundary conditions. However, designers often face with the lack of reliable thermophysical input data for various envelope components as well as with some intrinsic limitations in the simulation models, especially to describe the geometric features and peculiarities of the heritage buildings. This paper attempts to bridge this knowledge gap, providing critical factors and possible solutions to support hygrothermal simulations of historical buildings. The information collected in the present work could be used by researchers, specialists and policy-makers involved in the conservation of building’s heritage, who need to address a detailed study of the hygrothermal performance of historical buildings thorugh dynamic simulation tools