From Heat Pumps to Roof Tiles: The Roadmap to Net-Zero Buildings in New Construction and Renovation

Net-zero energy buildings produce as much energy as they consume, marking a significant advancement in sustainable construction. Achieving this energy balance in practice requires combining high-performance designs, renewable energy sources, energy-efficient HVAC systems and integrated smart technologies. This paper examines the current legislation and performance requirements for zero-emission buildings, featuring case studies and expert insights to chart the path toward decarbonizing Europe's building stock. 

_{What Is a Net Zero Building?}

While there are several definitions of net zero (or net-zero energy) buildings, the term is mostly used to describe housing structures that are designed to produce as much energy as they consume. Given the challenge of achieving this, the EU has introduced an additional term, 'nearly-zero energy buildings' (NZEBs), referring to houses that have a high energy performance combined with low energy needs, mostly met by on-site or nearby renewable sources. 

As per Europe's Energy Performance of Buildings Directive, all new buildings in the EU must be NZEBs since 2020. While each of the Member States has set its own minimum energy performance requirements, the common features of NZEBs include energy-efficient design and construction, adoption of renewable energy sources and incorporation of energy storage and management systems.

The requirements are to be tightened even further in the next few years. The recast Directive, adopted in May 2024, mandates that all new publicly owned buildings will have to be zero-emission buildings starting from 2028, meaning they should have no on-site carbon emissions from fossil fuels and very high energy performance. The same requirement will apply to all new buildings starting from 2030. The minimal energy needs still required for net-zero emission buildings will have to be met from on-site or nearby renewable energy sources. 

_{Why Are Net-Zero Emission Buildings Important?}

Buildings currently account for 40% of the EU's energy consumption and 35% of its energy-related greenhouse gas emissions. Natural gas remains the most common energy source for heating buildings, followed by oil. Thus, the transition to net-zero emission buildings is crucial for achieving the goals of the EU Green Deal by 2050. 

Advancements in building materials, energy systems and design enable stepping away from unsustainable construction practices, replacing the EU's building stock with structures that are both eco-friendly and economical for end users.

_{How to Build a Net-Zero Energy Home: Design Matters} 

As the adoption of alternative energy technologies rises and the costs of traditional fossil fuels increase, the interest in green building techniques has been growing among real estate developers, contractors and customers. 

The energy efficiency of a building depends on multiple factors — including site location, climate, availability of energy sources as well as construction materials, insulation and HVAC systems — all of which have to be considered during the design phase. 

Modern construction and design technologies help identify the most economical and energy-efficient solutions for each project, minimizing the risks of human errors. For example, Building Information Modelling (BIM) tools enable automatic clash detection. Via in-depth analysis and simulation, BIM models provide information about a building's operational behavior even before the construction starts, avoiding costly errors later on, explains Giuseppe Palmeri, Data Strategy Team Lead at wienerberger:

"BIM allows for analyzing and simulating the behavior of the building and making changes as needed. For example, it is possible to check how energy-efficient your building will be with single-glazed windows and how the energy efficiency changes with double-glazed windows."  

Relying on digital models, stakeholders foresee how their choices align with the current sustainability and energy-efficiency requirements, including green building certification schemes, such as BREEAM, LEED, and DGNB.

_{The Four Pillars of Net-Zero Buildings}

The key elements that must be addressed in zero-emission construction are the quality of the building envelope, the type of energy used, the installed HVAC and lighting solutions, and the integration of smart energy management.

_{Insulated Building Envelope}

The building envelope — comprising the foundation, roof, exterior walls, windows and doors — serves as the barrier between the interior and exterior environments of a building and is critical to ensuring comfortable, energy-efficient and healthy living year-round.  

A highly insulated building envelope minimizes heat transfer to/from a building, reducing the energy required for heating and cooling. Adequate insulation in exterior walls, attics and foundations combined with triple or quadruple-glazed windows has become essential to meet increasingly stringent energy-efficiency requirements.

A growing green trend is the so-called passive houses that feature super-insulated, airtight envelopes, allowing for energy savings of up to 90% compared to typical building structures.

_{Renewable Energy Sources}

Approximately two-thirds of the energy used for heating and cooling buildings in the EU still comes from fossil fuels. To achieve net-zero energy status, buildings must be equipped with a renewable energy system that can offset their consumption needs. At the household or community level, solar panels are currently the most used option, but the adoption of other technologies, such as air-source and geothermal heat pumps, is also increasing.  

Reaching net zero is also possible for buildings that rely on district heating and cooling by increasing the share of renewables in the energy carrier mix. Integrating geothermal, solar or waste heat energy not only brings down the associated carbon emissions but can also contribute to improved air quality and lower heating/cooling bills. 

Communities relying on fossil-free district heating and cooling already exist across Europe. For instance, part of Grilstad Marina in Trondheim, Norway, uses a system harnessing the thermal energy of seawater. The innovative solution has saved 3-4 million kilowatt hours in a six-year period, underscoring the importance of integrating local renewable energy sources to create district heating and cooling solutions that are both sustainable and feasible.

_{Energy-Efficient HVAC and Appliances}

Heating, ventilation, and air conditioning (HVAC) systems, along with artificial lighting and electrical appliances, contribute to a building's energy consumption. While initiatives such as the Energy Label have increased awareness among Europeans about the savings and benefits of energy-efficient appliances and light sources, adopting economical and environmentally friendly space heating and cooling solutions has been slower. 

Convection heating systems, such as radiators or forced-air appliances, create warmth by heating the air and have to operate at relatively high temperatures to achieve comfortable living environments. In practice, this translates to high energy consumption and costly bills to end users. The situation is no different when it comes to cooling: air conditioning and fans remain the most common technologies, accounting for nearly 20% of global electricity consumption.

Low-consumption heating and cooling alternatives are available. Radiant systems, such as hydronic heating and cooling, warm or cool objects and surfaces directly, requiring by far less energy and lower running temperatures to provide equal or even superior indoor comfort. For instance, if a forced-air system is set to maintain an indoor temperature of 22° C for residents to feel comfortable, a radiant hydronic system can achieve the same comfort level at 20° C. 

Ivan Milenovic, Heating and Cooling Business Development Manager at Pipelife, explains that, just by switching from convection to radiation, homeowners can expect energy savings of ~10%. However, even greater bill reductions are achieved by combining radiant systems with alternative energy sources:

"On-site renewable heat sources, such as air-source and geothermal heat pumps, are best-suited for low-temperature heating and cooling solutions like radiant systems. The combination is often used in zero-energy buildings and passive houses." 

_{Smart Energy Management}

Even the most energy-efficient buildings can have varying consumption depending on the needs and habits of residents. A recent study focusing on building energy improvements in Italy and the UK found that the actual energy savings were significantly lower than estimated. In the observed UK homes, the total energy savings were only 14% in contrast to the predicted calculation of 88%. In Italy, the respective figures were 38% and 67%. The researchers concluded that some households did not save energy due to the rebound effect, meaning that their energy use and habits differed before and after energy-efficiency improvements. 

This is where automation and smart energy management systems come in — allowing for monitoring and optimizing a building's energy consumption based on occupancy patterns, appliance and light source use, humidity, outdoor temperatures and other factors. 

Smart building technology relies on interconnected IoT devices and sensors that enable data exchange among various building systems. For example, the operation of heating and cooling systems can be enhanced using zone controlling, set usage time, and weather compensation features, resulting in additional savings for homeowners. Smart buildings can also optimize the use of lighting sources and energy-intensive appliances, monitor indoor air quality, alert on maintenance issues and incorporate advanced security measures. 

The benefits of smart energy management systems go beyond meeting carbon emission targets; they help homeowners better understand their consumption patterns, reduce bills and maintain comfortable, healthy and safe living environments.

_{Reaching Net Zero in Renovation}

The recast Energy Performance of Buildings Directive does not concern merely new builds; it also mandates that Member States increase deep renovation efforts and incentives to ensure all existing buildings meet zero-emission standards by 2050. 

With 85-95% of Europe's current buildings still expected to be in use by midcentury, most of which are not energy efficient, this is a critical challenge. Approximately 40 million Europeans currently struggle to adequately heat their homes, highlighting the urgent need to address Europe's aging building stock. 

The current large-scale renovation rate across the bloc remains low, only 1.2 % per year. This figure must be at least doubled to decarbonize Europe's buildings by midcentury.  

Europe's Renovation Wave Strategy, published in 2020, aims to tackle energy poverty by renovating worst-performing buildings and public buildings as well as decarbonizing heating and cooling. Given that over two-thirds of the EU population reside in privately owned houses, educating homeowners about the benefits, technical possibilities and available financial support remains crucial to ending energy poverty, eliminating solid-fuel-heating related air pollution and reaching net-zero emissions. 

Several Member States have already initiated local subsidy schemes and tax reductions, incentivizing insulation and window replacement and installing on-site renewable energy sources, such as heat pumps and solar panels. 

_{The Future of Net-Zero Construction}

As the EU continues to tighten regulations and push for zero-emission buildings in the next decades, the construction industry must innovate and adapt. The integration of smart building technologies along with high-performance building envelopes, increased affordability of on-site renewable energy sources and energy-efficient HVAC solutions has created a new demand wave for sustainable housing. Yet, a tailored, multifaceted approach is required for each project to ensure the calculated energy savings do not remain on paper.

The dual approach of constructing new net zero buildings and retrofitting the old ones will play a key role in reducing the EU's carbon footprint if the bloc is to reach the Green Deal's goals. Closer collaboration between governments, industry stakeholders and the public remains essential to address the current challenges and fully embrace the opportunities of net-zero construction, paving the way for a more affordable, efficient and sustainable building stock across Europe.