The landscape of space and water heating is undergoing a transformative shift. Fossil fuels, traditionally dominating energy use, are giving way to efficient and low-carbon heating technologies. Here we offer a glimpse into the current state, global challenges, and strategies for achieving sustainable heating solutions in buildings.
Space and water heating demand still heavily relies on fossil fuels globally, constituting almost two-thirds of energy use. Despite this, there's optimism as efficient and low-carbon heating technologies, like heat pumps, gain momentum, particularly in North America and Europe. To achieve Net Zero Emissions (NZE) by 2050, a rapid scale-up of efficiency improvements, fuel and technology shifting, and power sector decarbonization is imperative. By the end of this decade, measures aim to cut buildings' heating-related emissions by half, a significant step towards a sustainable future. While emissions from heating in buildings remained flat in 2022, substantial reductions are needed to align with the NZE Scenario, where heating emissions accounted for over 80% of direct CO2 emissions in the buildings sector (International Energy Agency, 2023).
The challenge lies in reaching 100% adoption of clean heating technologies before 2030, as outlined in the NZE Scenario. The NZE Scenario emphasizes electrification and innovative smart heating control systems, paving the way for optimized heating, reduced emissions, and less strain on electricity grids. The adoption of clean heating technologies is not just a choice but a necessity in navigating the global energy landscape (International Energy Agency, 2023).
From 2021, all new EU buildings must be nearly Zero-Energy Buildings (nZEB). This shift aligns with global efforts to reduce energy consumption and combat CO2 emissions. Nordic nations lead in sustainable energy practices, facing challenges in apartment design due to small roof areas and limited sunlight in winter (Gibbons and Javed, 2022). Despite these challenges, surging trends in Low-Energy Apartment Buildings (LEABs) are observed in Norway, Sweden, and Finland already before 2020 (Figure 1).
Figure 1. Annual percentage of new residential floor area accounted for by apartment buildings in Sweden, Finland and Norway. Figure from Gibbons and Javed, 2022. used under CC license BY 4.0.
Regulatory impacts on heating, ventilation and air conditioning (HVAC) systems, revealed through Energy Performance Certificates (EPCs) comparisons, play a crucial role in shaping building efficiency and sustainability efforts. Building efficiency improves over time, with heating solutions in LEABs varying. Current trends indicate a shift towards optimizing systems to meet domestic hot water (DHW) demand. The synergy of efficient HVAC systems, on-site renewable energy integration, and regulatory advancements paves the way for a sustainable, energy-efficient built environment (Gibbons and Javed, 2022).
As the world strives for sustainable development, the focus on energy-efficient solutions intensifies in the realm of heating systems. A recent study by Bocian et al. (2022) highlights key strategies: incorporating renewable sources, enhancing heating networks, promoting cogeneration, and reducing water temperatures.
DHW systems significantly impact building energy consumption. Recent research highlights a global trend, indicating that 11-32% of total energy demand is allocated to meet DHW needs (Bocian et al., 2022). Moreover, in nZEBs, an astonishing 50% of energy consumption is attributed to DHW (Gibbons and Javed, 2022). Methods like hydraulic optimization (Klimczak et al., 2022), control valves to limit water flow during periods of lower hot water consumption, and temperature adjustments are suggested to minimize heat losses balancing Legionella prevention and energy savings. The need for more field studies is emphasized to develop accurate methods for evaluating energy efficiency in diverse building types. Identifying and addressing excessive heat losses in circulation pipes will advance DHW systems (Bocian et al., 2022).