• Energy Research

Though the energy consumption of buildings is supposed to decrease after a retrofit, several studies show that the energy performance does not increase as much as it would be expected and that a significant gap between the estimated and the real energy savings - called “rebound effect” - occurs. This deviation can partly depend on the model used for the energy performance evaluation, but changes in the occupants’ behavior after a thermal retrofit of an existing dwelling are also revealed. The paper examines the influences of occupant behavior on the energy savings for some retrofitted Italian residential representative buildings. Some typical use patterns are defined according to statistics of the national census of population and dwellings and the expectations of the building occupants are specified before and after the retrofit. The main objective is to investigate the elasticity of the energy consumption in function of the occupancy parameters before and after the application of high energy efficiency improvements. The analysis is carried out by means of a simplified energy performance assessment model. The outcomes of this study consist in defining synthetic indicators for the quantitative assessment of the rebound effect.

Abstract The study presents some results of the on-going European Project, RePublic_ZEB, on the refurbishment of the public building stock towards nearly Zero Energy Building (nZEB). The work is focused on the application of the nZEB requirements to two existing public buildings representative of the 1960s in Northern Italy. Many packages of energy efficiency measures that comply with nZEB requirements are identified and evaluated. The aim is to promote energy efficient but also cost-effective solutions for the Italian building stock refurbishment. The results are presented in terms of «package of measures», energy consumption, global costs, actualized pay-back period and CO2 emission.

Abstract Directive 2010/31/EU requires since 2019 the new public buildings and since 2021 all the new buildings to be nearly zero-energy (nZEB). In Italy, as in many geographical contexts, the existing buildings represent the majority of the building stock and equally the largest and most cost-effective energy saving potential. This study presents the energy performance calculations carried out by means of quasi-steady state method for some Italian reference buildings refurbished into nZEB. The results are presented in terms of “packages of measures” and potential energy reductions. The differences among measures depending on building type and climatic conditions are discussed.

In the paper a methodology for identifying the cost-optimal levels of minimum energy performance requirements (according to Directive 2010/31/EU), already introduced in a previous work, is applied to Italian reference office buildings, different in the glazed area. The optimal energy efficiency measures, resulting from the application of a quasi-steady state numerical model, are then modelled by means of a dynamic simulation tool and the deviations are discussed. The aim is to validate the simplified model and to pave the way for future researches on cost optimality by applying energy performance simulation.

Abstract The European residential building stock is largely composed of buildings with poor energy performance, therefore basic retrofit actions could lead to significant energy savings. However, energy refurbishment measures should be identified in accurate way, taking into account the technical viability and aiming both to increase the building energy performance and to restrain the costs. The present article investigates the effects of different measures applied to the Italian residential building stock by using the building typology, which consists of 120 building types, representative of six construction ages, four building sizes and five climatic zones. A quasi-steady state model has been used to calculate the energy performance; the economic evaluation has been carried out as specified in the EU cost-optimal comparative methodology (Directive 2010/31/EU). The most effective measures and packages of measures, in terms of energy saving and global cost reduction, are identified and discussed. The results are addressed to important purposes for energy policy, as for instance: (a) to provide political authorities with the most effective energy efficiency measures as to encourage retrofit processes through the allocation of financial incentives, (b) to offer a knowledge-base for developing energy refurbishment scenarios of residential building stocks and forecasting future energy resource demand.

This study presents some preliminary results of an on-going European Project, RePublic-ZEB [1], where an analysis is conducted for identifying the cost optimal levels for the existing buildings, towards nearly Zero Energy Buildings (nZEB) performance. The analysis is applied to the reference building for an existing office building in five different countries: Italy, Portugal, Romania, Spain and Greece. The evaluation tool uses a new cost optimization procedure based on a sequential search-optimization technique considering discrete options [2] is applied and the results will be presented in terms of optimal "package of measures", energy consumption and global costs. Finally a cross-country analysis will be performed. © 2015 The Authors. Peer Reviewed

Abstract As reported in the scientific literature and mentioned in building energy performance legislation, the thermal inertia of the opaque building envelope can have a significant positive impact on the reduction of summer indoor overheating, of space cooling peak load and of electricity consumption. At the early stages of the envelope design, there is a need to use simplified as well as effective parameters to correctly characterize the thermal performance of the opaque envelope under dynamic conditions. In this work, a new methodology to describe the dynamic thermal behavior of opaque components is proposed. The approach is based on the harmonic parameters specified in ISO 13786 but it also takes into account realistic boundary conditions for different orientations and solar absorptance values. New equivalent thermal parameters are determined by means of dynamic simulations. The use of these parameters to assess the conduction heat flow rate by means of a simplified model is validated through a comparison with the results of a dynamic simulation. The method presented in the article represents an improvement with respect to the parameters usually applied at the early design stage to thermally characterize the opaque envelope of the building under dynamic conditions. In fact, it allows simplified but reliable performance parameters referring to actual boundary conditions to be obtained. The application potential of the proposed methodology lies in the drawing-up of catalogues and technical standards that supply the values of the new equivalent thermal parameters for different technical solutions.