In December 2019, European Union countries signed the European Green Deal, whose main objective is to achieve a 55% reduction in emissions by 2030 and net greenhouse gas emissions by 2050.

The Deal aims to make Europe the world’s first climate-neutral continent, with proposals intended to ensure that all sectors of the economy are able to meet this challenge in areas such as sustainable transport, industrial development and clean energy systems, building renovation for greener lifestyles, and the protection of nature, the planet, and health.

Following the signing of the Deal, the EU has continued to introduce laws and regulatory frameworks to guide the economy towards a circular and sustainable future.

In relation to the construction sector, and due to the urgent need to adapt the existing building stock to this new reality, the European Commission proposes requiring Member States to renovate at least 3% of the total floor area of all public buildings each year, setting a benchmark of 49% renewable energy in buildings by 2030, and requiring Member States to increase the use of renewable energy for heating and cooling by 1.1% each year until 2030. [1]

European Taxonomy

The European Taxonomy is a regulation adopted in June 2020 that establishes an EU-wide classification—a common language for determining which economic activities (including building) can be considered sustainable—in order to support the transition to a carbon-neutral, resilient, and resource-efficient economy.

In other words, it provides the financial sector with a definition of sustainable investment, described as follows:

“An environmentally sustainable activity must make a substantial contribution to at least one of the six objectives pursued:

a) climate change mitigation;

b) climate change adaptation;

c) the sustainable use and protection of water and marine resources;

d) the transition to a circular economy;

e) pollution prevention and control;

f) the protection and restoration of biodiversity and ecosystems.

Without harming any of the other five, in line with the principle of doing no significant harm.” [3]

In addition, it must ensure two minimum objectives: the building cannot be intended for the extraction, storage, production, or transport of fossil fuels, and the companies involved must comply with minimum social safeguards regarding human and labour rights.

These performance thresholds are known as “technical screening criteria” and, in addition to identifying which activities are already environmentally friendly, they also help companies, project developers, and issuers access green financing to improve their environmental performance. In this way, they enable the development of low-carbon sectors and the decarbonisation of high-carbon ones.

To prevent the increasingly widespread phenomenon known as greenwashing, which often goes hand in hand with progress on sustainability, this regulation introduces obligations for financial market participants regarding the disclosure of pre-contractual information and subsequent periodic reports, in relation to the environmental objectives of the economic activity, as well as a description of the approach and measures aimed at achieving those environmental objectives.

Accordingly, companies required to publish non-financial information must report information on their revenues, expenditures, and assets related to processes associated with economic activities classified as sustainable.

This section is complemented by the regulation adopted a few months earlier, in November 2019, on sustainability-related disclosures in the financial services sector, which specifies these requirements and distinguishes between companies with good governance practices and those that invest exclusively in sustainable products or services. [4]

The Level(s) project

The Level(s) project was developed by the European Commission in close collaboration with key stakeholders such as Skanska, Saint-Gobain, Sustainable Building Alliance, and the Green Building Council in each country.

In this way, the EU brought together two leading private companies in the construction sector with two non-profit organisations whose aim is to build alliances between countries—connecting institutions, universities, and research and development centres with private stakeholders.

The initial premises aim to link a building’s environmental impact to the EU’s priorities in the circular economy. It is important that it is an accessible tool, so an open-source assessment framework will be developed.

On September 28, 2017, the Level(s) pilot phase began, lasting 2 years (2017–2019): a beta version that, over this period, was tested by professionals in more than 130 buildings across 21 European countries.

In 2020, a new, easier-to-understand methodology was published—Level(s) Methodology v2—which already applied the construction life cycle. In January 2021, two technical guidance reports were published to support this pilot phase, covering successes and potential modifications.

The first technical report is essentially an introduction to Level(s) and how it works, titled User Manual 1: Introduction to the Level(s) common framework, developed by the JRC Technical Reports consultancy. [5] It is a theoretical framework that addresses frequently asked questions such as who should use this manual and why, and refocuses on the need for a common language, describing the main objectives in a very visual and straightforward way.

In the final part of the document, titled Thinking sustainability, key concepts for Level(s) and the EU are developed on how to drive economic change that ensures sustainability, and concepts are defined as the reflection progresses.

The topics are as follows: full life cycle and circular thinking; closing the gap between design and actual building performance; how to achieve a sustainable renovation; and how sustainability can positively influence a property’s market value.

The second technical report provides detailed guidance on carrying out performance assessments and is titled User Manual 2: Setting up a project to use the Level(s) common framework.[6] It is essentially divided into two distinct sections: establishing a project plan and completing the building description. For the first section, planning tables are provided with questions to be completed with the team’s responses, as well as grids with all indicators and the different project phases to provide a view of the life cycle and the implications of the built environment. Finally, the building description focuses on four aspects: location and climate, building typology and age, how the building will be used, and the construction model and its characteristics.

The Level(s) framework

Level(s) is currently a voluntary reporting framework to improve the sustainability of buildings, despite the challenges posed by its voluntary nature. However, short-term objectives include making it mandatory for public buildings, following the logic of the requirements set out in the recent regulation on NZEB Nearly Zero Energy Buildings, with deadlines for when compliance will become compulsory.

Therefore, Level(s) establishes common units of measurement and basic calculation methodologies through a set of indicators that both draw inspiration from and serve as the basis for many European building-related policies. As a result, compliance with these indicators will increasingly be required at both European and national levels.

Its target audience is both public and private, arguing that collaboration between the two is not only necessary but also enriching, and likewise framing the model of economic change towards sustainability. Stakeholders may include construction professionals, building assessment systems, investor reporting tools, or public-sector initiatives.

In addition, the disclosure of these indicators improves understanding of how buildings affect the environment. The third technical document, Levels User Manual 3, was published in July 2021 and is divided into one document per indicator.

Each document provides a brief introductory summary, step-by-step instructions on how to apply the indicator at different levels, and supporting guidance. Some indicators also have associated Excel templates to help calculate or record data.

Project phases

The Level(s) framework is a staged procedure for properly assessing a building’s life cycle.

To eliminate differences between design performance, as-built performance, and occupied building performance, users can report on the indicators at different phases of a project:

– design phase: the indicators at this preliminary design stage are based on prior calculations of building performance—that is, on a hypothesis that makes it possible to adjust geometry and select materials according to their specifications. This is primarily a qualitative analysis.

– construction phase: performance calculations at this stage become more precise and apply corrections to the previous ones, as they are based on as-built drawings—that is, the set of drawings redrawn once the works are completed to compare them with the original drawings. Geometry may be adjusted slightly, or the actual performance of certain materials may be calculated. Therefore, at this stage it is already possible to quantify the building’s design performance using the common units of measurement and reference calculation methods established by the Level(s) framework.

– occupancy phase: throughout the occupancy phase—that is, the only period in the building’s service life when it is used for the purpose for which it was conceived—it is essential to account for consumption and performance in order to calibrate actual behaviour according to climatic seasons, as this is a sampling period. Data is therefore collected to monitor the project’s real performance.

– post-occupancy phase: once the period of use has ended, with all the data collected over the years it is possible to develop a measured performance baseline that takes into account the time factor, maintenance, occupant flow, etc.

Performance indicators of the Level(s) framework

Each indicator has been designed to link a building’s impact to the European Union’s sustainability priorities.

There are 16 criteria grouped into 6 macro-objectives that emphasise environmental performance, health and wellbeing, life-cycle cost and value, and potential risks to future performance. These objectives can, in turn, be grouped into 3 thematic areas.

For each indicator, a “stepwise” approach is possible, allowing users to move from basic-level calculation methods to a full life-cycle assessment (LCA).

1. Greenhouse gas emissions over the building’s life cycle

1.1. Energy efficiency in the use phase [7]

1.2. Life-cycle global warming potential (GWP) [8]

2. Material life cycles that are circular and resource-efficient

2.1. Bill of quantities, materials, and service lives [9]

2.2. Construction and Demolition Waste (CDW) and materials [10]

2.3. Design for adaptability and renovation [11]

2.4. Calculator

3. Efficient use of water resources

3.1. Water consumption in the use phase [12]

4. Healthy and comfortable spaces

4.1. Indoor air quality [13]

4.2. Time outside the thermal comfort range [14]

4.3. Lighting and visual comfort [15]

4.4. Acoustics and noise protection [16]

5. Climate change adaptation and resilience

5.1. Protection of occupants’ health and thermal comfort [17]

5.2. Increased risk of extreme weather events [18]

5.3. Sustainable drainage [19]

6. Full building life-cycle cost and value

6.1. Life-cycle costs [20]

6.2. Value creation and exposure risk [21]

1. Greenhouse gas emissions over the building’s life cycle

This section, which relates to Sustainable Development Goal number 7—ensuring access to affordable, reliable, sustainable, modern, and above all non-polluting energy—covers two indicators: energy efficiency in the use phase and the building life-cycle global warming potential.

Life-cycle assessment (LCA) is a method for calculating the environmental impact of a product throughout all stages of its life. An LCA of a building typically involves assessing its entire life cycle, that is, all phases: raw material supply, manufacturing of construction products, the construction process, use, demolition, and material recycling.

The Paris Agreement highlights the importance of assessing environmental impact and more actively reducing activities that contribute to global warming. To calculate these effects in the construction sector, the most effective method is life-cycle assessment (LCA), because it considers multiple criteria and the full environmental impact throughout the life of a product or building.

1.1. Energy efficiency in the use phase [7]

The guide begins by summarising essential definitions for understanding the building’s energy performance, including that of Nearly zero-energy building:

“It means, according to the Energy Performance of Buildings Directive, a building that has very high energy performance. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby.”

To measure the building’s energy performance, the guide for this indicator goes back to the design phase and the aspects that must be considered, following the principles of bioclimatic architecture to adapt the building to its surroundings. It also discusses incorporating the concept of renovation, high-quality construction materials, and smart monitoring and control systems. The energy consumption calculation will take into account the energy needed to heat and cool spaces, supply hot water, light spaces, and operate the building’s technical systems, as well as any energy exported from the building, where applicable.

1.2. Life-cycle global warming potential (GWP) [8]

This indicator aims to quantify the contributions of a building’s global warming potential throughout its life cycle, from “cradle” (the extraction of raw materials used in the building’s construction) to “grave” (the deconstruction of the building and how its construction materials are treated, i.e., recovery, reuse, recycling, and disposal).

The “cradle-to-grave” thinking enables building design solutions that seek the optimal balance between the embodied carbon of building materials and carbon emissions during the use phase. A step further is to apply the principles of the circular economy in architecture with “cradle-to-cradle” thinking, understanding a building as a repository of carbon-intensive resources for many decades and exploring designs that facilitate future reuse and recycling at the end of the building’s life – what the guide calls “design for deconstruction.”

Thus, the indicator provides a calculation tool that measures the greenhouse gas (GHG) emissions associated with the building at different stages of its life cycle. This concept is sometimes referred to as carbon footprint assessment or whole life carbon measurement.

As in the previous indicator, a checklist of relevant design concepts is established, taking into account the following aspects, focusing on good prior design rather than mere calculation:

– Efficient building form: Minimize the surface-to-volume ratio of a building and individual residential units, as well as their height, to improve material efficiency and minimize energy use.

– Optimized NZEB construction: Consider the potential trade-off between reducing CO₂ emissions in the use phase to achieve NZEB performance levels and the embodied energy CO₂ emissions associated with the manufacture of higher-performance insulation, facade and wall systems, windows, structural thermal mass, and renewable energy technologies.

– Optimized material utilization and circular value: Consider the possibility of reusing an existing building’s structure or optimizing the structural design of a new building to minimize material use. Consider options to minimize or even design out waste generated during product manufacturing, on-site construction to optimize material utilization on a construction site.

– Extend the lifespan of buildings and components: Consider options to extend the lifespan of significant building components and minimize the number of replacement and renovation cycles.

– Design for adaptability: Consider the potential for the building’s design to adapt and be flexible to changing market and occupant needs in the future, to extend the building’s lifespan, including its structure and main elements.

– Design for deconstruction: Consider how the building’s design and information records on the building’s material bank can facilitate future deconstruction at the end of its life to recover materials for reuse and recycling.

2. Material life cycles that are circular and resource-efficient

Although we are seeing how all macro-objectives, indicators, and sustainable development goals are closely related, and the need to use circular materials with minimal embodied carbon becomes evident, this section focuses on the life cycle of materials and SDG 12, which advocates for ensuring sustainable production and responsible consumption patterns.

To facilitate understanding of this objective in relation to the life cycle of construction materials, the guide divides it into 4 indicators or sub-sections: list of quantities, materials, and service lives; Construction and Demolition Waste (CDW) and materials; design for adaptability and renovation; and an Excel template for the corresponding calculations.

2.1. Bill of quantities, materials, and service lives [9]

The first indicator, “List of quantities, materials, and service lives,” establishes a checklist with 6 design concepts that are developed throughout the document:

– Consider the building form over the inherent material efficiency of the structure.

– For a given structural design, consider the scope for optimizing material efficiency.

– Consider the potential trade-offs of material-efficient design options.

– Durable and repairable building components and systems.

– Optimal use of fit-out materials.

– Incorporation of recycled materials.

Thus, comparison tables are shown between the efficiency of the most common materials (brick, mortar cement, and concrete) according to the housing format (detached, semi-detached, or block), graphs that relate the exponential increase in the amount of structural steel and the embodied carbon of construction materials in relation to the increase in a building’s height, average service lives for each material, etc.

2.2. Construction and Demolition Waste (CDW) and materials [10]

The second indicator focuses on “Construction and Demolition Waste (CDW) and materials” with the following design concepts for the checklist:

– Setting relevant targets or key performance indicators.

– The influence of project type on CDW generation and management.

– Pre-demolition audit (if demolition activities are carried out).

– Good construction practice.

– Waste Management Plan scheme.

– Principles of “Buildings as material banks.”

It provides very interesting information on possible end markets for the reuse or recycling of recovered materials, with up to three alternatives for their reuse, recycling, or recovery. In addition, it names various examples of construction and demolition waste traceability software such as the Belgian project Tracimat, which has received funding from the European Union’s Horizon 2020 research and innovation program.

2.3. Design for adaptability and renovation [11]

The third indicator on adaptability and renovation discusses changes of use, emphasizing the need to consider from the outset the current and future needs of occupants, future demand changes in the real estate market, and lifestyle changes in the case of a residential property.

3. Efficient use of water resources

The third macro-objective encompasses a single indicator, which refers to the need for efficient use of water resources, in total relation to Sustainable Development Goal number 6: Ensure availability and sustainable management of water and sanitation for all.

This SDG aims to significantly increase, from now until 2030, the efficient use of water resources in all sectors to ensure the sustainability of freshwater extraction and supply to address water scarcity and reduce the number of people suffering from water shortages.

At the Spanish level, the biggest regulatory gap is found in water. Although Spain has both legislation titled Water Law [22] and strategies such as the DSEAR Plan, National Plan for purification, sanitation, efficiency, saving, and reuse [23], none make direct reference to building. Even the specific regulations of the Technical Building Code Basic Document on Health and Water Supply, CTE-DB HS4, are insufficient for the Level(s) indicators. [24]

3.1. Water consumption in the use phase [12]

This indicator establishes the following checklist with 5 design concepts that are developed throughout the document:

– Consider how to reduce water demand from sanitary facilities.

– Understand water scarcity in the context of the building’s location.

– Consider rainwater harvesting and greywater reuse.

– Consider incorporating vegetation on building surfaces.

– Potential metering plans.

It defines indices such as the Water Exploitation Index (WEI+) which calculates the flow rate of resource extraction in relation to the use of renewable water resources and highlights the importance of rainwater harvesting and greywater reuse, both associated with treatments and the need for volumetric calculation of demand and supply.

At all times, it warns of the relative importance of regional water scarcity, stating that while improving the water efficiency of buildings through design options is important in all cases due to the environmental benefits it can provide, it is even more important in areas suffering from continuous or seasonal water scarcity.

Furthermore, in relation to green building surfaces, it establishes criteria for selecting plant species and efficient irrigation systems, along with the advantages offered by the presence of such landscaped areas.

4. Healthy and comfortable spaces

If we look at the weighting of indicators for each macro-objective, we can see that the certification gives greater relevance to objectives 2 and 4, meaning it focuses on the life cycle of materials and their efficiency, and the quality of spaces in relation to the health of their users. Similarly, the third of the Sustainable Development Goals also focuses on Health, ensuring healthy lives and promoting well-being for all at all ages.

It also argues that health emergencies, such as that derived from COVID-19, pose a global risk and have shown that preparedness is vital, as the large differences in countries’ capacities to deal with the health crisis largely stem from the importance given to this aspect at a preventive level.

Thus, the objective is divided into 4 indicators: indoor air quality, time out of thermal comfort range, lighting and visual comfort, and acoustics and noise protection.

4.1. Indoor air quality [13]

The first indicator on indoor environmental quality at the Spanish regulatory level is extensively covered in the Technical Building Code Basic Document on Health in sections 3 and 6, referring to Indoor Air Quality and Protection against Radon Exposure. [24]

This indicator is important because 1,800 deaths occur annually in Europe due to poor IAQ, according to the European Environment Agency. It has become a significant public health issue as there are numerous potential sources of pollutants within buildings: construction materials, decorative products, maintenance, and furniture.

When measuring indoor air quality, the behavior in different phases of the project must be taken into account, due to the complex cause-and-effect relationships that influence the indoor air parameters to be quantified.

It describes in detail the need to maintain an environment with low volatile organic compound (VOC) emissions through limit tables for the different substances. The main sources of VOCs in indoor air are continuous low-level emissions from building materials and intermittent peaks from the use of chemical products (most commonly for surface cleaning). The first on the list and therefore considered the most dangerous is formaldehyde, which is present in numerous finishing materials such as paints and varnishes. It therefore recommends the measurement and monitoring of indoor pollutant concentrations.

In addition, it warns of the danger of external pollutants such as radon, particulate matter, and benzene. In this case, as it is pollution coming from outside, depending on the quality of this environment according to the European air quality index, different ventilation strategies are proposed that take into account the need for filtering outside air.

4.2. Time outside the thermal comfort range [14]

Thermal comfort has its own Spanish regulation in the RITE, Regulation of Thermal Installations in Buildings [25]

Level(s) certification considers the following design concepts to minimize time out of thermal comfort range:

– Building design for inherent thermal resilience.

For the design of buildings with thermal resilience, it recommends the use of thermally massive building structures that leverage the intrinsic inertia of materials to delay temperature changes, thus moderating internal comfort conditions. In relation to the envelope and facade, it recommends selecting materials for their solar reflectance effect and thermal resistance, thereby reducing the absorption and transmission of solar radiation into the building. Furthermore, it pays special attention to the design of fresh air entry routes into the building through shaded outdoor spaces or underground systems to minimize its temperature.

– Factors that can cause localized indoor thermal discomfort.

These factors to avoid are vertical air temperature differences, floor temperature, radiant temperature asymmetry, and different occupant activity levels.

– The shading and microclimate benefits of nature-based solutions.

At this point, the document explains the importance of vegetation in buildings, such as green roofs, or inside buildings, such as plants, as they provide shade and moderate outdoor air and surface temperatures around the building. Additionally, using permeable ground instead of a hard surface around the building helps moderate external temperatures.

Next, it develops a calculation system called the “green factor” that scores how the shading and cooling function of vegetation and soil affects a building’s design. This factor can be used as an indicator of the ecosystem services provided by green infrastructure.

4.3. Lighting and visual comfort [15]

This section is important in the Spanish context since the concept of luminous comfort lacks its own regulatory development and is practically absent from other regulations.

In Level(s) certification, it is extensively developed, considering the following design concepts that include metrics to quantify intensities and minimum and maximum thresholds.

– Daylight: maximizing its useful contribution.

There are several methods to understand the amount of natural light that can enter a building.

The “daylight factor” is the traditional metric, which compares the illuminance level of daylight in an unobstructed field with that of the illuminance at a defined point within the room. Although the daylight factor is a useful metric, it fails to characterize the building based on annual climatic conditions. Therefore, it recommends dynamically simulating daylight penetration into a building with data from the typical meteorological year representative of the building’s location.

The document also discusses considering the view as part of daylight quality. Taking into account the concept of biophilia, i.e., the human need to establish a connection with nature, it explains how users appreciate an outdoor view, including the landscape, sky, and other external surroundings.

– Daylight: minimizing its negative impact.

Potential negative impacts of daylight are glare, overheating due to excessive solar heat gains, and the subsequent increase in cooling energy costs. These can be considered during the conceptual design stage, as they are again affected by the building’s orientation, volume, and glazing.

– Light levels and distribution for visual comfort.

The objective of electric lighting installation is to completely replace, or complement and enhance, the contribution of natural light to the space, ensuring that light is distributed in sufficient quantity and quality. The main quantity and quality metrics to consider are: light levels, light distribution, and contrast rendering.

In this section, the document makes a note about circadian lighting, i.e., the human body’s daily sleep/wake cycle, and how it can influence our health. The spectral properties, intensity, distribution, and timing of light delivery are factors that play an important role in stimulating or suppressing the body’s natural circadian system. That is why it is important to develop a design that includes so-called circadian or integrative lighting, for which multiple new metrics have been developed.

– Optimized and personalized control for visual comfort.

The quantity, distribution, and spectral qualities of lighting must respond to the individual needs of occupants based on the tasks being performed, visual acuity, and individual preferences. Traditionally, lighting design has tried to accommodate this by anticipating the worst-case scenario, which inevitably leads to unnecessarily high light levels and increased energy consumption, so the correct light must be provided, in the correct quantity, at the correct time, and in the correct place.

– Light source quality for electric light sources.

The quality of the light source depends on the lamp or luminaire in which the light sources are installed and their spectral output, which is also related to color temperature.

4.4. Acoustics and noise protection [16]

In Spanish regulations, the regulations on Noise Protection are included in the Technical Building Code Basic Document on Noise Protection (CTE-DB HR). [26]

Level(s) certification considers the following design concepts to ensure users’ acoustic comfort:

– Minimize environmental noise from traffic and industry.

– Acoustic insulation to prevent discomfort from airborne and impact noise.

– Extension of performance criteria to lower frequencies.

– Room acoustics and environmental noise from human activity, minimizing reverberation time by increasing sound absorption area.

– Optimization of room acoustics in open-plan offices.

5. Climate change adaptation and resilience

Becoming aware of the impact of climate change on all countries across all continents may not be easy, but it is necessary. It means accepting the uncertainty of an unknown scenario, understanding that 2019 was the second hottest year on record and that this is nothing more than evidence that weather systems are changing, sea levels are rising, and weather events are becoming increasingly extreme.

That’s why one of the 6 macro-objectives encompasses the need to adapt our building stock, in line with SDG 13 on Climate Action which, recognising this same phenomenon, calls for urgent measures to combat climate change and its impacts, in order to save lives and livelihoods.

5.1. Protection of occupants’ health and thermal comfort [17]

The first indicator refers to the need to protect occupants’ health and thermal comfort, which it proposes to ensure through the following design concepts: identify and assess risk factors, design for comfortable thermal conditions, take into account the site’s specific conditions, and take into account the specific conditions of the renovation.

5.2. Increased risk of extreme weather events [18]

The second indicator addresses the higher-risk scenario of extreme weather events, so it will be necessary to: lay the groundwork for adaptation, assess potential risks and vulnerabilities to extreme weather events in the region and on the specific building plot, identify possible adaptation actions, and assess the costs and benefits of adaptation actions.

To this end, the European Environment Agency has developed a Europe-wide map viewer with indicators of the vulnerabilities of different regions to heat, river flooding, coastal flooding, pluvial flooding, droughts, wildfires, and other metrics not strictly related to this Level(s) indicator but no less important: water scarcity, diseases, and social vulnerability.

5.3. Sustainable drainage [19]

Given the high risk of flooding from different causes such as sea-level rise or storm risk, the third indicator focuses on sustainable drainage. To this end, it proposes familiarising the design team with sustainable drainage systems, assessing the site’s flood risk, and the costs and benefits of sustainable drainage.