Nearly-zero Energy Research Articles

Identification of the Retrofit Actions to Achieve Cost-Optimal and NZEB Levels for Residential Buildings in Istanbul Considering the Remaining Building Lifetime

Cost-optimal and nearly-zero energy building (NZEB) levels are two interrelated concepts identified for upgrading energy performance of buildings in Europe. In parallel, many research activities on retrofitting existing buildings in Turkey follow the methodology framework introduced by the European Commission. However, in Turkey, there is a process called “urban transformation” due to the earthquake risk, but the practice is based on new construction after demolishment of existing buildings. Especially in Istanbul, this process has been conducted rapidly. This specific aspect requires assessment of cost-optimal retrofit analyses considering the remaining lifespan of analysed buildings. This study presents a cost-optimality assessment method for retrofitting towards NZEB in Turkey. The method integrates payback period and investment cost assessment to the methodology in order to obtain whole picture for retrofit alternatives. In the paper, suggested method is applied to a reference residential building in Istanbul. After the initial cost-optimal analyses, payback periods and initial investment costs for selected retrofit packages are assessed considering the future lifespan of the building. Together with these, possible subsidy opportunities are also investigated. Results show that, if the expected future lifespan is higher than 10 years, retrofit actions achieving 56.2kWh/m2y primary energy consumption level are considerable. Subsidies are beneficial to obtain reasonable initial investment costs.

Commissioning of thermal performance of prefabricated timber frame insulation elements for nZEB renovation

The current study contains a commissioning of thermal performance of highly insulated building envelope, located in cold and humid Estonian climate. The focus is on the renovation of old apartment building to nearly-zero energy building with prefabricated timber frame insulation elements with designed thermal transmittances U=0.10-0.12 W/(m2∙K). Air tightness, heat flux and temperatures were measured after renovation. Results of commissioning are showing some deviations from designed values, possibly caused by internal convection, improper tightening of joints of elements and poor quality of sealing of layers which must be kept airtight. The results have shown that analysis of designed solutions before, during and after renovation is worthwhile. Thorough inspection and strict rules of quality control on work site are essential for high-quality, sustainable outcomes of renovation with timber frame insulation elements and to guarantee designed thermal performance.

Energetic, Cost, and Comfort Performance of a Nearly-Zero Energy Building Including Rule-Based Control of Four Sources of Energy Flexibility

A focal point of ongoing research is matching the energy demand in the built environment to the energy supply from onsite generation, to maximize the self-consumption, and from the energy grids, to lower energy costs and reduce peak loads on the system. Energy flexibility addresses this task by modulating the energy demand in a building according to dynamic criteria such as electricity prices or onsite generation. This study addresses the potential of building performance simulation with real time rule-based control that provides energy flexibility based on onsite generation and hourly electricity prices, prioritizing energy matching, and reducing costs. The novelty relies on investigating four sources of energy flexibility simultaneously: shiftable machine loads, charging/discharging of batteries, hot-water storage tanks, and the building’s mass. The energy matching and flexibility actions provided a decrease of up to 4% in annual energy costs, yet risk increasing the cost by 9% when the savings are offset by the increase in the energy demand. As well, the method for price categorization strongly influences the cost performance of the flexibility actions. The outcomes of this study provide insight to energy flexibility sources in nearly-zero energy buildings and how their outcomes are affected by price thresholds.

Composition and Operation of a Semi-Virtual Renewable Energy-based Building Emulator

This paper describes the composition and operation of a semi-virtual energy system and building emulator designed for studying hybrid grid interactions of a modern nearly-zero energy building. The system consists of a real part for energy production (PV panels and micro-wind turbine), storage (batteries and hot water storage tanks) and conversion (ground-source heat pump GSHP and electric heater) combined with a virtual part that models a single-family house in the computer simulation program TRNSYS. A Labview program is used for communication between the real and virtual parts. Measurement data from six periods selected for study between September 2015 and February 2016 are analyzed. The data indicate that during the study, the total electricity consumption was 1290 kWh, divided to 44/38/18% between household appliances, GSHP and electric heater, respectively. The local net production was 250 kWh, or 19% of the total demand. PV, which was heavily concentrated in fall, accounted for 54% of the production. Wind production was winter-centered. The electrical energy matching aspects of the system are represented with two indices: OEFe (on-site electrical energy fraction), the fraction of the building electrical demand covered by local production, and OEMe (on-site electrical energy matching), the ratio of the building’s self-consumption to the total local production. The matching capability of the energy system was found poor due to daily and seasonal mismatches between production and demand. The small net production compared to demand led to small OEFe and large OEMe values overall.

A Short review on the use of renewable energies and model predictive control in buildings

This short review is based on an overview of the most recent works of the literature related to climatization in buildings. A total number of 40 relevant papers that have been published in the last years in prestigious international journals have been reviewed with the aim of showing the current state of the art in this field. It is very important as the new European regulations that will be applied in the next years in the construction of buildings, aiming to achieve nearly-Zero Energy Buildings (nZEBs), will require a multidisciplinary work in the different areas that affect the design of buildings. For this reason, it is relevant the envelope, the user behavior, the Heating, Ventilation and Air Conditioning applied (HVAC) and the influence of the meteorological conditions, among others. But apart from this, it would be very interesting any other alternative which helped to reach these targets. This article proposes the possibility of using Model Predictive Control (MPC) besides to Renewable Energies in order to optimize the energy management of air-conditioning in public and office buildings through a radiant floor by solar system and high-performance heat pump systems for their heating / cooling. In this paper, a short review is initially exposed where the different "Input data and information" are analyzed, to end up proposing an Operative for a Predictive Control using these Renewable Energies.

Occupant behaviour lifestyles and effects on building energy use: Investigation on high and low performing building features

Occupant behaviour is known to be one of the key sources of uncertainty in the prediction of building energy use. Extended literature reviews linked the large performance gaps between residential buildings with same properties and similar climate conditions to the way occupants interact with the building envelope and systems. Furthermore, in the last decades, more stringent energy codes have led to energy efficient design strategies with the aim of reaching the nearly-zero energy target. The success of these strategies is now heavily dependent on how the occupants interact with the building, or rather, on the energy-related lifestyles they assume. In line with this, the present study employs building simulations to demonstrate the potential impact of different occupant behaviour lifestyles on the energy use of a Mediterranean (i) residential nearly-zero energy building (nZEB) under-construction and a (ii) Reference Building (RB) whose envelope-driven loads dominate the consumption profile.

A high performance home in the Mediterranean climate: from the design principle to actual measurements

Experience developed in the northern European countries led, in the last decades, to standard and shared procedures for the design and construction of passive houses and similar high performance buildings. These approaches are specifically developed for cold climates, therefore cannot be directly applied to the Mediterranean climate, where substantially different climatic conditions must be challenged.The design and early monitoring of a customized zero energy house, located in Sicily, is proposed as an exemplary case study for the future generation of high performance and nearly-zero energy buildings in the Mediterranean area. The key role played by the control of heat gains, and the correct use of thermal mass is highlighted, showing similarities and differences with passive houses built in the North Europe. The measurements of energy and environmental performance of the building show the effectiveness of the response of the adopted design approach to the specific climatic conditions.

Achieving nearly zero energy buildings in Cyprus, through building performance simulations, based on the use of innovative energy technologies

In Europe, 27% of final energy use occurs in residential buildings and another 14% in tertiary buildings, making the "building sector" the largest end-use energy consumer with over 40% of the total. The energy consumed within European buildings averages to 70-230 kWh/m2 per year. Achieving a nearly zero energy (NZE) target in buildings is both necessary and crucial.This paper presents the methodology and initial findings from modelling and simulating advanced energy conservation and generation technologies in two case study buildings in the area of Peyia, Cyprus. The simulations were performed through free-running and thermostatically-controlled conditions by means of Design Builder software, in order to achieve the nearly zero energy (NZE) target. The specific objectives are both a reduction of the net regulated energy to an average of 0-20 kWh/m2 per year, as well as a generation of at least 50 kWh/m2 per year in each building. The findings of the study are that the nearly zero energy target is achievable if a majority of the energy used in the buildings comes from renewable energy technologies and if the regulated loads of the buildings are reduced through the use of energy conservation technologies.

Application of ground-to-air heat exchanger for preheating of supply air

This study focuses on assessing the contribution of the passive ground-coupled air heat exchanger system to decreasing the energy consumption of air conditioning and ventilation systems for office buildings in the Latvian climate conditions. The theoretical part of the thesis deals with methods of office building ventilation, supply air preheating and heat recovery as well as particularities of using ground-coupled air heat exchangers, their design parameters and their joint impact on the thermal performance. The engineering project part includes a ventilation system for an office building with an integrated ground-coupled air heat exchanger. By simulating energy consumption of the ventilation system for a duration of one year, the thesis analyzes the contribution of the heat exchanger to the overall energy consumption, which totals 9.53 MWh and 4.02 MWh a year, according to the desired parameters of the indoor climate. The possible alternative heat recovery solutions are investigated to reach by European Regional Development Fund project Nr.1.1.1.1/16/A/048 “NEARLY ZERO ENERGY SOLUTIONS FOR UNCLASSIFIED BUILDINGS”.

The analysis of the hot water consumption and energy performance before and after renovation in multi-apartment buildings

The article presents the results of hot water supply system analysis. Taking into account that the current consumption of hot water differs from normative values, real measured data of hot water consumption in multi-apartment buildings from year 2013 until year 2015 have been analyzed. Also, the thermal energy consumption for hot water preparation has been analyzed. Based on aggregated data and taking into account the fact that renovated systems of hot water supply in existing multi-apartment buildings have same pipelines’ diameters, it was analyzed how these systems are economically and energy efficient. For the study, residential buildings in Riga, which have different architectural and engineering solutions for hot water supply systems, were selected. The study was based on thermal energy consumption measurements, which were taken at the individual heating system’s manifolds. This study was done in order to develop database on hot water consumption in civil buildings and define difference in key performance criteria in unclassified buildings. Obtained results allows to reach European Regional Development Fund project “NEARLY ZERO ENERGY SOLUTIONS FOR UNCLASSIFIED BUILDINGS” Nr. 1.1.1.116A048 main targets.

NZEB Renovation with Prefabricated Modular Panels

The reduction of energy use in buildings is expected to be reached in part by fulfilling several requirements of the low- and nearly-zero energy buildings (nZEB) policy. The improvement of energy performance of buildings offers a huge potential for energy savings as the annual replacement of existing stock is only 1–2%. The efficient way to accomplish the purpose of the nZEB is to apply the integrated design process and application of prefabricated modular renovation elements on a large scale. In the Horizon2020 MORE-CONNECT project we developed prefabricated modular elements for the building envelope insulation and with the use of these elements, the nZEB renovation will be realized as a pilot. The study includes a complex of measures: hygrothermal measurements and analysis of moisture safety, prefabricated highly-insulated facade and roof modular renovation elements, full repair of indoor areas, rebuilding of balconies, insulation of cellar constructions, the full modernization of heating and ventilation systems. Ventilation ducts are integrated into the modular panels to minimize supply ductworks in apartments. Roof modules include solar panels and collectors for renewable energy production as well as a system for rainwater drainage. All technical systems and building modules will be equipped with monitoring systems and data will be logged periodically.

NZEB Renovation of Multi-Storey Building with Prefabricated Modular Panels

Reduction of energy use in buildings in EU is expected to be reached with help of fulfilling of requirements of low and nearly-zero energy buildings (nZEB) policy. The efficient way to accomplish the purpose of the nZEB is to apply the integrated design process, considering the long-term sustainability and building costs as a one setup. The multi-storey large concrete element building is renovated to nZEB as a Horizon2020 MORE-CONNECT project pilot in Tallinn. The study of that project includes complex of measures: hygrothermal measurements and analysis, highly insulated facade and roof elements, the full modernisation of heating and ventilation systems. Ventilation ducts are installed into the modular panels to minimize supply ductworks in apartments. Roof panels include solar panels and collectors for renewable energy production. All technical systems will be equipped with monitoring systems and data will be logged periodically. The designed thermal transmittance is U≤0.11W/m2K for walls, U≤0.10W/m2K for roof and U≤0.80W/m2K for windows and external doors. The analyse, design and renovation process of the integrated nZEB design method gave us a unique experience, showing weak links in the chain and helping to prevent faults in the whole process in the future.

Energy consumption and urban sprawl: Evidence for the Spanish case

Residential electricity consumption constitutes one of the largest sources of Spanish final energy demand. To improve electricity savings, policies oriented towards efficiency in residential consumption, such as replacement of appliances or the construction of nearly-zero energy buildings, have been suggested and implemented. However, the potential relevance of urban structural characteristics, such as the increase in detached houses in sprawling residential areas, has not often been considered. The aim of this research is to analyse the relevance of living in a detached house located in a dispersed urban area to household electricity consumption. Thus, an electricity consumption model is estimated by using household socioeconomic variables and including urban characteristics as its determinants, such us the level of urban agglomeration or whether families live in detached-sprawling homes. The model is estimated by using 2014 Household Budget Survey (HBS) microdata and applying Ordinary Least Squares (OLS) as well as quantile regressions (QR) as econometric procedures. Endogeneity problems are corrected by means of instrumental variables. The results confirm that living in a detached house significantly increases electricity consumption, whereas urban agglomerations have the opposite effect. Sprawl is occurring rapidly in Spanish cities, and according to our results, it could constitute a relevant source of increase in electricity demand in the following years.

Impact of co-benefits on the assessment of energy related building renovation with a nearly-zero energy target

The reduction of the energy consumption and carbon emissions in the building sector is an important target for actions to mitigate the climate changes and different actions are being carried out to promote a transition to a low carbon built environment. However, present standards are mainly focused on new buildings which may result counter-productive in existing ones, due to their technical, functional and economic constraints. One of the most common problems in the current way of assessing building renovation scenarios is that only energy savings and cost are considered, disregarding additional benefits.Many studies, based on real cases, have already highlighted the relevance of these so-called co-benefits, which can be felt at the building level (and therefore they should be considered in the definition of the renovation measures) and also at the level of society.The present investigation has been developed under the scope of IEA EBC Annex 56 project, and a method to integrate co-benefits in the evaluation of the renovation scenarios towards both the nearly-zero emissions and the nearly-zero energy objectives is proposed. It has been applied to case-studies from several European countries and based on subsequent findings recommendations for policy makers and professional owners are presented.

Modular retrofitting solution of buildings based on 3D scanning

Building stock is one of the crucial energy consumers in Europe. The majority of the European residential and public buildings were constructed after the Second World War. The external building envelope of these buildings has very poor thermal insulation properties with regards to modern requirements. There are several well known building retrofitting technologies such as rendered and double facades. These retrofitting technologies require large amount of on-site human working mounts. However, there might be significant limitations in mounting processes of the unclassified buildings such as prisons, military buildings and other buildings with specific safety requirements. In scope of this article the benefits of modular retrofitting solutions are taken into consideration. The paper presents the results of the architectural project development specifics as well as selection of the optimal modular panel layout, integration of existing communication and modular panels junctions solutions.This paper is prepared in the scope of work done within the European Regional Development Fund project “NEARLY ZERO ENERGY SOLUTIONS FOR UNCLASSIFIED BUILDINGS”.

Nearly-zero Energy Buildings: Cost-optimal Analysis of Building Envelope Characteristics

Energy consumption in the building sector continues to increase in the entire world and therefore, the determination of cost-optimal solutions towards nearly zero-energy buildings is a serious challenge. The present study is focused on the optimal thermal features of the building envelope, including thermal insulation on wall, roof and ground floor as well as the optimal window properties, in order to achieve nearly-zero energy buildings in the climate conditions of Cyprus. A systematic and robust scientific procedure was adapted in order to determine levels of energy performance leading to minimum life-cycle cost. Energy simulations of different reference test-cell buildings were performed, based on the external envelope's surface to total building volume ratio, and the cost-optimal performance levels were calculated in accordance with Regulation 244/2012/EU, taking into consideration three different climate areas of Cyprus – the cities of Limassol and Nicosia and the mountainous area of Saittas. Both the optimal thermal transmittance coefficient of the external envelope elements and the optimal window properties for each reference test-cell building were calculated. The results demonstrate that the cost-optimal energy performance levels of reference test-cell buildings in Cyprus are considerably higher than the national minimum requirements. Moreover, a linear correlation was found between the optimal (mean) thermal transmission coefficient and the study area, a result that underlines the necessity of forming three independent climate zones in Cyprus instead of one that exists today.

The Role of the Building Envelope in Achieving Nearly-zero Energy Buildings (nZEBs)

The 2010 Energy Performance of Buildings Directive (EPBD) requires all new buildings to be nearly-zero energy buildings (nZEBs) by 2020. A strict definition of nZEB is yet to be defined by the legal framework of each European country. However, the basic principles of nZEBs are the reduction of their energy demands to minimum and, subsequently, the coverage of their low energy demands in a great extent by renewable energy sources.This study focuses on the potential reduction of energy demands in a typical Greek residential building. A model building, representative to the average Greek residential building was designed and used as model. The effect of various parameters on the energy demand of the building, such as insulation, openings and shading devices, was investigated and evaluated. The model building was examined in all four climate zones of Greece using dynamic simulation software tools to define the energy demands. The results suggest that the most efficient constructive solutions for every climate zone lay on various combinations of parameters. The right combination for each climate zone can contribute to a significant energy saving that rises up to 30% and reduce the total annual energy demand of the building to less than 50 kWh/m2.

Distributed resources coordination inside nearly-zero energy buildings providing grid voltage support from a symmetrical component perspective

In this work, the authors propose a new coordination method for smart distribution networks (SDN) with nearly-zero energy buildings (nZEB). The proposed coordination procedure considers a central controller that runs a state estimation of the grid and calculates the optimum set-points for the buildings. Inside each building, the building management system (BMS) manages the converters used by the dispatchable generators (DG), the renewable generators (RG) and the energy storage system (ESS) to fulfil (as far as possible), the central controller request.In the paper, the unbalanced behaviour of the grid is considered, so the optimum references for the symmetrical component currents in the converters are calculated. The proposed method reduces the network unbalance and the total losses. In addition, buildings with energy surplus can support other neighbours with energy deficit. The present paper is focused on how the BMS calculates the optimum references for all converters placed inside each building. The main contribution of the paper is the use of the symmetrical component approach at building level in order to generate the best references for all converters inside the building.

Automated roof window control system to address overheating on renovated houses: Summertime assessment and intercomparison

Major and deep energy renovations on residential buildings are expected in Europe over the next several years. The current developments towards nearly-zero energy houses in building efficiency have increased the overheating occurrences indoors. For house users summer thermal discomfort is an unknown challenge that they have not faced in the past. The objectives of this study is to highlight the problem of overheating in energy renovated dwellings in temperate climates and to investigate the ability of automated roof window control systems to address the risk during the peak summer period. The assessment of the indoor environment was conducted in a typical two-storey house, close to Copenhagen. Both dynamic and static criteria were used to carry out risk evaluation.The assessment of the monitored data of the house verifies the fact that active and passive ventilation and shading systems, if manually controlled, cannot guarantee high quality indoor environment. The use of automated roof window control system may significantly decreases the overheating risk without any significant compromise of the indoor air quality. The developed system is analyzed in detail. Suggestions for future work are also proposed.

Refurbishment of the Residential Building Stock toward the Nearly-Zero Energy Target Through the Application of the Building Typology

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.