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Concept: Urban heat island (UHI) effect mitigation - Nearly Zero Energy Buildings (NZEBs)

The design and operation of zero or very low energy buildings started in the 2000s and even earlier. The basic idea is to use energy conservation technologies combined with renewable energy systems to decrease as much as possible the energy use of buildings (see Figure 1). Nearly-Zero Energy Buildings (NZEBs) have continuously gained acceptance by the market and the research community and several thousands of such buildings have been built and monitored.  

The NZEB principle has been adopted as the current and future policy by the European Union. Indeed, according to the EU Directive on Energy Performance of Buildings (EPBD) [1], new buildings occupied by public authorities had to be NZEBs by December 31, 2018 and all new buildings had to comply by December 31, 2020. NZEBs are defined as buildings with a very high energy performance, as determined in accordance with Annex I of the EPBD. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources produced on-site or nearby. The EPBD does not prescribe a uniform approach for implementing NZEBs. It states that Member States shall detail NZEB definitions, reflecting national, regional or local conditions, and including a numerical indicator of primary energy use expressed in kWh/m2/year. As such, the requirements show heterogeneity across the various Member States [2]. On average, NZEBs energy performance levels appear 10% higher than the benchmark levels recommended by the Commission in 2016 [3] in most Member States. 

Most common NZEB technologies include both passive solutions (e.g. sunshade, natural ventilation and lighting, night cooling), and active solutions (e.g. mechanical ventilation with heat recovery, heat pumps in combination with efficient lighting, appliances, and envelope). The typical envelope U-values fall in the ranges 0.15 – 0.20 W/m²K (walls) and 0.10 – 0.25 W/m²K (roofs). Regarding renewable energy sources, PV and solar thermal are frequently used [4]. 

Numerous building design procedures and principles are employed to achieve the nearly zero energy target resulting in a variety of potential solutions that present significant cost differences. Some favour excessive use of photovoltaics or other renewables and almost an insignificant use of energy conservation technologies, disregarding the primal objective of high energy performance and thus minimal energy needs.  

However, the Commission’s proposal to revise the EPBD [5] (December 2021) makes a step forward from current NZEB to zero-emission building (ZEB), aligning the energy performance requirement for new buildings to the longer-term climate neutrality goal and “energy efficiency first principle”. According to the directive’s proposal, a ZEB is defined as a building with a very high energy performance, with the very low amount of energy still required fully covered by energy from renewable sources generated on-site, from  renewable energy community or from a district heating and cooling system. The ZEB requirement should apply as of 1 January 2030 to all new buildings, and as of 1 January 2027 to all new buildings occupied or owned by public authorities. 

Figure 1. Concept of a NZEB  [2] 

 

Both NZEB and ZEB can be autonomous or connected to an energy infrastructure. Most of the existing low or zero energy buildings are connected to the grid.  

Various options exist concerning renewable energy supply. Figure 2 presents those applied in international energy calculation methodologies, ordered following the location of the energy supply option with respect to the building.   

Figure 2: Overview of possible renewable supply options, [6] 

Several concerns about the additional cost induced by zero energy buildings especially for the low income population are expressed. To minimize the cost, several studies exist aiming to investigate the necessary investments to build and run zero energy buildings in Europe, [7,8]. Increasing experience, industrial development on energy conservation and renewable energy technologies and the massive construction of zero energy buildings has resulted in a considerable decrease of the cost of zero energy buildings. However, given the current and future cost of energy and the additional cost induced by global and regional climate change, investments related to zero energy buildings are necessary and justified.  

Figure 3: A zero energy Building in Poland 

Figure 4: A zero energy office building in Belgium  

Figure 5: A zero energy building in Lucia Spain 

Figure 6: A zero energy building in the UK 

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Climate resilienceAnalytics and modellingBuildingEnergyIndustryMaterialsTechnology
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