nZEB Target Research Articles

Re-designing a temporary pavilion into a NZEB open lab for a university campus

During the Milan Design Week 2018, a temporary pavilion - “Delight The Light” – has been design and built - as press room for Officina Tamborrino - using their own products as construction technologies. This paper explains the evolution of this project from a temporary architecture into an NZEB open lab for university students. The introduction of innovative multilayer insulator materials characterized by high heat-reflecting properties and the tailored envelope design ensure the satisfaction of comfort both in winter and summer season and reduced drastically the time of constructions. The process, followed to reach the NZEB target, is based on performance-based design analysis. In particular the validation phase has foreseen a very detailed modelling steps on the building model through dynamic thermal simulations with finite element method to validate its thermal and hygrometric performances, coupled with daylighting and fluid dynamics simulations to consider also the users behaviour and well-being during the design stage.

Building-to-vehicle-to-building approach for the NZEB target at a micro-grid level: a comprehensive sensitivity and parametric post-optimality analysis

This paper focuses on a novel energy management approach for cluster of buildings connected in micro-grids by taking advantages from plug-in electric vehicles considered as vector devices for renewable energy exchanges, besides additional high-power appliances and house electricity sources. Such approach allows accelerating the development of nearly zero energy buildings and promoting the deployment of renewable energy sources at a micro grid level. To this aim, a dynamic simulation model, implemented in MatLab was developed for the building energy demands and loads assessment. To show the potentiality of the considered concept and approach, a case study based on a micro-grid consisting of a house and an office building connected by an electric vehicle is presented. The optimization of three different layouts, where electricity is alternatively produced by tilted roof or vertical façade photovoltaic panels is conducted by means of a parametric analysis performed by varying the vehicles energy use, battery capacities and solar field size. Preliminary results show that, by considering economic criteria, by exploiting the renewable energy production on and off-site, the buildings final demands decrease to values lower than those commonly considered for NZEBs.

Investigating the potential impact of energy-efficient measures for retrofitting existing UK hotels to reach the nearly zero energy building (nZEB) standard

The existing non-residential building stock can generally be considered energy-inefficient. The ECUK 2017 report states that the final energy consumption for commercial buildings remained static. The 2010 recast Energy Performance Building Directive (EPBD) has set out a requirement for commercial and residential buildings to be nearly Zero Energy Buildings (nZEBs) by 2020. Despite this, within the UK, a definition does not exist at the national level for commercial nZEBs (new or existing). This paper utilises the EU zebra2020 data tool to set a standard based on the existing UK nZEB commercial building stock. The aim of this paper is to investigate and assess the potential of various energy-efficient measures (EEMs) and their contribution to reducing energy consumption, primary energy consumption (PEC), and CO2 emissions whilst taking into consideration the energy and cost savings of those measures. The analysis is carried out using Thermal Analysis Simulation software (Tas, Edsl). The model validation obtained a performance gap of less than 5%. The results show that it is possible to achieve the nZEB standard for older UK hotel buildings if several measures are implemented and the initial selection of EEMs is carefully investigated. Based on the results, reaching the nZEB target should first take into consideration improving the building fabric and/or building envelope elements to lower the energy demand. Once the energy demand of the building is lowered, the incorporation of a renewable/microgeneration system is essential to meeting the nZEB target.

Transformation of an Office Building into a Nearly Zero Energy Building (nZEB): Implications for Thermal and Visual Comfort and Energy Performance

Directive 2010/31/EU promotes the refurbishment of existing buildings to change them into nearly zero-energy buildings (nZEBs). Within this framework, it is of crucial importance to guarantee the best trade-off between energy performance and indoor environmental quality (IEQ). The implications of a global refurbishment scenario on thermal and visual comfort are assessed in this paper pertaining to an existing office building. The retrofit actions applied to achieve the nZEB target consist of a combination of envelope and technical building systems refurbishment measures, involving both HVAC and lighting. Energy and comfort calculations were carried out through dynamic simulation using Energy Plus and DIVA, for the thermal and visual performance assessments, respectively. The results point out that energy retrofit actions on the building envelope would lead to significant improvements in the thermal performance, regarding both energy savings (−37% of the annual primary energy for heating) and thermal comfort. However, a daylighting reduction would occur with a consequent higher electricity demand for lighting (36%). The research presents a detailed approach applicable to further analyses aimed at optimizing the energy efficiency measures in order to reduce the imbalance between visual and thermal comfort and to ensure the best performance in both domains.

Energy evaluations of an innovative multi-storey wooden near Zero Energy Building designed for Mediterranean areas

In order to respect the energy savings directives, worldwide designers look toward more sustainable buildings, especially with tower configurations to reduce the footprint in urban environments. The implementation of multi-storey buildings with a massive employment of wooden materials represents a feasible solution; however, in Mediterranean areas the seismic risk renders the design process very challenging. Consequently, designers often prefer hybrid structures where a reinforced concrete core guarantees structural safety whereas the wooden elements used for the building envelope confer efficient energy performances. Furthermore, in warm climates the attainment of the near Zero Energy Building (nZEB) is a difficult target because in the presence of insulated envelopes the cooling requirements could negatively affect the building energy consumption. In this paper, the energy performance of an innovative multi-storey wooden nZEB expressly designed to meet the requirements of the Mediterranean areas, are presented. In particular, the structural safety was attained by combining a timber frame with a precise layout of cross laminated timber (CLT) panels. Once the structural behaviour was verified, a parametric analysis developed in TRNSYS allowed determination of the best building-plant configuration for the achievement of the nZEB target.

Experimental Nearly Zero Energy Building with Green Technology – Renovation Pilot through Passive House Expertise

The paper presents the preliminary planning of a demonstration pilot for exemplary renovation of an existing building (“Solar House 1 – Campina”) towards nZEB level using Passive House principles and technologies. The “Solar House” was one of the lighthouses of solar energy developments in the ‘80s in Romania, being built in 1977-1978 in Campina (Centre-South Romania) and represented an experimental building using innovative solar technologies for DHW preparation, active and passive space heating. The decision of transforming the existing building in a demonstration pilot nZEB with green materials was taken and the feasibility study is currently underway. The pilot aims to analyse and test, the cost effectiveness of Passive House (PH) technologies integration in a deep renovation process with the view to achieve the fixed nZEB levels, as an exemplary case study demonstrating the benefits and feasibility of applying PH principles and energy performance evaluation in real context. Both approaches of applying the renovation standard EnerPHit and targeting Passive House criteria are discussed together with the nZEB targets, while the analysis of technical (energy performance) and economic (total costs) feasibility is presented. The proposed building will act as a training and consultancy centre in Campina - created as a model for achieving greater energy efficiency and environmental responsibility in Romania.

Social housing refurbishment in Mediterranean climate: Cost-optimal analysis towards the n-ZEB target

The cost-optimal analysis represents a useful tool to stimulate the refurbishment of existing buildings, highlighting the minimal global cost that private or public users have to sustain in order to attain appreciable energy savings in the building life span. The identification of precise interventions on the building-plant system could steer legislators to the emanation of appropriate financial incentives in order to make the refurbishment of existing edifices more attractive. However, the cost-optimal solutions cannot be generalized as they are strongly influenced by the initial conditions and by the climatic context. In this paper, a traditional social housing unit, realized in Italy during the 1970s, largely widespread and strongly energy-consuming, was analysed in two different climatic zones belonging to the Italian territory. Suitable interventions were identified for the reduction of energy requirements for heating, cooling and domestic hot water production. These analyses were carried out by using the same simulation tool for energy and economic performances, highlighting the deviances among the cost-optimal solutions, the n-ZEB target and the minimal interventions for the containment of energy consumptions imposed by the current Italian legislation for buildings subjected to refurbishment.

Assessing the overheating risks in Italian existing school buildings renovated with nZEB targets

Energy retrofit projects following nearly zero-energy buildings (nZEB) requirements often pay a little attention to Indoor Environmental Quality of the building. This aspect is extremely important in school buildings, as they are frequented mostly by young people, who are affected more by a healthy environment. In this context, starting from a reference case, overheating risks in existing school buildings considered for energy renovation were investigated through TRNSYS 16. Four building configurations were evaluated (existing, nZEB, nZEB with external shadings, nZEB with external shadings and night ventilation) and the influence of several parameters was taken into account (climate, orientation, building level). The aim of this paper is to understand if nZEB standards applied to Italian school buildings guarantee good indoor thermal conditions and which building configuration can be more advantaged by these standards. Furthermore, even if overheating risk is qualitatively recognized in insulated and air tight buildings, quantitative assessments are still missing for the Italian building stock. The intent of this research is to provide preliminary data on this topic in order to lead to a more conscious choice of retrofit strategies as a compromise between energy performances and indoor environmental quality.

A new procedure of energy audit and cost analysis for the transformation of a school into a nearly zero-energy building

The article presents the fundamental steps of building refurbishment toward the nZEB target; it is based on a detailed energy audit and on a financial analysis. The methodology starts from the set-up of a numerical model of the building, calibrated through actual data on operation, climate and energy consumption. Then, a cost-optimisation procedure is applied to identify the energy efficiency measures that determine the minimum global cost in 30 years lifetime. Finally, the measures are improved as to comply with the nZEB requirements and to be cost-effective as well. The methodology was applied to a high school in Torino.

On the optimal mix between lead-acid battery and thermal storage tank for PV and heat pump systems in high performance buildings

The coming into force of the European Directive 2009/28/CE [1] increases the role of renewable energy sources to satisfy the energy consumptions of new buildings and major renovations. In this respect, the vapor-compression heat pump coupled with PV panels is a promising solution and, consequently, it is increasingly used for residential heating applications. This HVAC solution is especially advantageous in high performance building when low temperature hydronic systems are adopted. However, in these buildings some issues arise in the HVAC control and the building might be easily subject to poor comfort conditions when approaching the nZEB target while maintaining economical convenience. Besides, the seasonal performance of the heating system is strongly dependent on the HVAC design. Hence, the optimal size of the storage components is a key aspect in order to maximize the renewable coverage factor, overcoming the shift in time between PV production and energy demand. For this reason, different strategies may be adopted such as the thermal storage tank or the electricity storage in lead-acid battery.This paper analyses the mix among the thermal storage tank, the lead-acid battery and the thermal capacitance of the building envelope for the optimal design solutions in three Italian climates. The complex interactions among building, occupants, weather conditions and HVAC systems are considered by means of a dynamic simulation tool. The optimal design solutions were studied, according to the cost optimal approach of the EPBD context, by means of a genetic algorithm developed in Matlab®. The energy performance for heating (EPh) and the net present value (NPV) are considered as competitive goals.

Overview and future challenges of nearly zero energy buildings (nZEB) design in Southern Europe

In times of great transition of the European construction sector to energy efficient and nearly zero energy buildings (nZEB), a market observation containing qualitative and quantitative indications should help to fill out some of the current gaps concerning the EU 2020 carbon targets. Next to the economic challenges, there are equally important factors that hinder renovating the existing residential building stock and adding newly constructed high performance buildings. Under these circumstances this paper summarises the findings of a cross-comparative study of the societal and technical barriers of nZEB implementation in 7 Southern European countries. The study analyses the present situation and provides an overview on future prospects for nZEB in Southern Europe. The result presents an overview of challenges and provides recommendations based on available empirical evidence to further lower those barriers in the European construction sector. The paper finds that the most Southern European countries are poorly prepared for nZEB implementation and especially to the challenge/opportunity of retrofitting existing buildings. Creating a common approach to further develop nZEB targets, concepts and definitions in synergy with the climatic, societal and technical state of progress in Southern Europe is essential. The paper provides recommendations for actions to shift the identified gaps into opportunities for future development of climate adaptive high performance buildings.

The significant imbalance of nZEB energy need for heating and cooling in Italian climatic zones

Building energy performance requirements aiming at the nZEB target have been recently established by the national legislation. In Italy, the requirements are verified through the notional reference building, whose U-values are reduced in two steps: up to 2018 and since 2019 for public buildings, and up to 2020 and since 2021 for all other buildings. This might cause a reduction of the heating need but an increase of the cooling need. The objective of the study is to investigate in which conditions and extent a significant imbalance of the energy needs occurs. Different building types and climatic zones are considered.

Attitudes and approaches of Irish retrofit industry professionals towards achieving nearly zero-energy buildings

PurposeThere is profound demand for higher skills and expertise in retrofitting the existing building stock of Europe. The delivery of low- or nearly zero-energy retrofits is highly dependent on technical expertise, adoption of new materials, methods of construction and innovative technologies. Future Irish national building regulations will adopt the Energy Performance of Buildings Directive vision of retrofitting existing buildings to higher energy efficiency standards. Construction industry stakeholders are key for the achievement of energy performance targets. Specifically, the purpose of this paper is to assess the attitudes, approaches and experiences of Irish construction professionals regarding energy efficient buildings, particularly nearly zero-energy buildings (nZEBs).Design/methodology/approachData were collected through a series of quantitative and qualitative methods, including a survey, a workshop and detailed interviews with professionals in the retrofit industry. The structure of this approach was informed by preliminary data and information available on the Irish construction sector.FindingsThere is a substantial amount of ambiguity and reluctance among the professionals in reaching the Irish nZEB targets. The growing retrofit industry demonstrates low-quality auditing and pre/post-retrofit analysis. Basic services and depth of retrofits are compromised by project budgets and marginal profits. Unaligned value supply chain, poor interaction among nZEB professionals and fragmented services are deterrents to industry standardisation.Practical implicationsThis study will enable construction industry stakeholders to make provisions for overcoming the barriers, gaps and challenges identified in the practices of the retrofit projects. It will also inform the formulation of policies that drive retrofit uptake.Social implicationsThis study has implications for understanding the social barriers existing in retrofit projects. Support from clients/owners has a diverse impact on energy performance and retrofit decisions. Community-based initiatives are key to unlock the promotion of nZEBs.Originality/valueThis paper provides an overview of current activities of retrofit professionals and analyses the barriers, gaps and challenges in the industry.

Energy efficient measure to upgrade a multistory residential in a nZEB

Developing nearly Zero Energy Buildings (nZEB) represents a path toward sustainable communities as required by the Energy Performance of Building Directive (EPBD). As consequence, nZEB target for new or existing buildings has become a mandatory priority for the multidisciplinary researchers involved in architectural engineering and building physics. Therefore, it is grown the interest in design energy efficient measures for reaching the nZEB status of both new and existing buildings. In this paper, the energy efficient measures adopted for reaching the nearly Zero Energy Building standards, for a multi-floor residential building located in the Mediterranean area, are presented. The extra cost necessary to reach the nZEB target have been calculated in the case of the energy retrofit of an existing building (scenario 1) and in the case to directly realize a building with achieve the nZEB status (scenario 2). Further, the two scenarios have been compared under financial point of view. The results of this paper provide to builders and stakeholder useful information for quantify the convenience to build a nZEB building in advance in order to prevent the additional expenses necessary by future energy retrofit programs.

Lean Production of Cost Optimal Wooden nZEB

The paper studies lean construction as a co-operational way of working to achieve nZEB targets and good indoor climate and to find new innovative combinations of building solutions. Main target of this paper is to assess energy efficiency, resource efficiency and economics of lean wooden nZEB compared to traditional wooden apartments. The results are based on lean construction literature survey, interviews and two case studies. According to a case calculation lean production of cost optimal wooden nZEB causes only about 115 €/m2 additional investment cost compared to construction, which only fulfils the minimum requirements as defined by building regulations. Annual savings in energy cost is about 8 €/m2 as present value. The annual life cycle cost is about 5 €/m2 as present value for the calculation period of 30 years. Also resale value and user-value (aesthetic value, thermal comfort, high quality of inner climate and good adjustable lightning) are a little higher compared to the traditional building. Calculations show that the total productivity of lean construction is about 20% better than of basic construction in both assessment cases.

Replicability of nZEBs on Real Estate Market in Mediterranean Countries

According to the recast of the Energy Performance of Buildings Directive and its target for the large-scale increase of nearly-zero energy buildings, nowadays a challenging task is the definition of standard high performing building types depending on location and specific climate conditions. The widespread replicability of nZEB types on the current real estate market could implement nZEB design scenarios attractive and affordable for construction companies and private investors. In particular, this research focuses on the definition of replicable HVAC system configurations with different features and efficiencies starting from a reference building located in a Mediterranean country. The configurations were applied to CorTau House, an nZEB under construction in Piedmont Region, a typical situation of European Mediterranean country where both winter and summer loads, together with humidity, have to be carefully controlled. Building envelope and HVAC system design were matched in order to optimize energy performance and indoor thermal comfort. The HVAC configurations, able to meet nZEB targets and to ensure optimal indoor comfort conditions, were combined with a performing building envelope, made of local construction materials, in order to assess which of them is more energy effective and economically viable. Cost-optimal types were identified and prospective replicability on building market was speculated. Finally, differences between private investor's and company construction's perspectives were discussed.

Cost optimality assessment of a single family house: Building and technical systems solutions for the nZEB target

Europe has set a clear path to guide Member States into the accomplishment of the nearly zero energy buildings (nZEBs) target. To this regard, within EPBD recast directive, a cost optimality procedure has been defined. This study presents different cost optimal solutions of building and technical systems for nZEBs in Italy. In total 40 economically and technically feasible energy efficiency measures for a high performing single family house were analyzed. Special attention was devoted to the study of the building technical systems. Achieving a net zero balance required a high efficient system combined with high insulation and a large PV system, which plays a key role in the nearly and net zero building energy balance. Three net zero energy balance solutions, based on all electric systems, were presented. Net ZEB solutions allowed also the building carbon footprint to be reduced by 40% compared to the reference case study. Without proper financial subsides, net ZEB solutions are still far for being economic feasible, having a global cost 212–313€/m2 higher than cost optimal solutions. In conclusion, this paper aims to present guidelines for designing reference building envelope and technical systems solution for residential nZEB.