29/01/2026 | Altro
The latest version of the European Directive (EU) 2024/1275 on the Energy Performance of Buildings (EPBD), dated 8 May 2024 [1], aims to improve the energy performance of buildings across the European Union, with the goal of achieving a net-zero emissions building stock by 2050. The Directive focuses primarily on the renovation of the existing building stock, which comprises over 220 million units built before 2001. Currently, 75% of EU buildings are still energy inefficient. Moreover, the construction and building sector remains the largest contributor to global emissions, accounting for 37% of the total.
Each EU Member State must develop a national plan to renovate its building stock to make it highly energy-efficient and decarbonized by 2050. The plan should:
Provide an overview of the national building stock, market barriers, deficiencies, and capacities in the construction, energy efficiency, and renewable energy sectors;
Define a roadmap with targets for 2030, 2040, and 2050 regarding annual renovation rates, primary energy consumption reduction, greenhouse gas emission reduction, and mitigation of energy poverty;
Include an overview of implemented and planned policies and measures;
Outline investment needs, funding sources, and administrative resources required for building renovations.
The decarbonization process of the existing building stock involves targeted deep energy renovation interventions, aimed at systematically reducing primary energy consumption. According to the European Commission’s requirements, by 2033, residential buildings must achieve an average reduction in primary energy consumption of 20–22%, while non-residential buildings must meet a minimum reduction target of 26%.
Achieving the objectives set by the Directive can be accomplished through high-efficiency building systems such as heat pumps, low-temperature radiant systems, air handling and distribution units, and advanced control systems—solutions that significantly reduce energy consumption and greenhouse gas emissions. Notably, the EPBD explicitly references “low-temperature heating systems” in Articles 5 and 13, urging Member States to define building element requirements to facilitate the integration of such systems.
In this context, within building renovations, low-profile and low-thermal-inertia radiant systems emerge as a key tool for sustainable, flexible, and high-performance retrofits, enhancing both energy efficiency and indoor environmental quality.
The HVAC market is increasingly turning towards low-profile, low-thermal-inertia solutions. These systems can be installed in both underfloor and ceiling radiant setups. Their reduced thickness makes them particularly suitable for energy retrofit interventions, where available space is often limited, while also offering advantages in terms of construction time and costs.
Their ability to respond quickly to changes in ambient temperature, thanks to low thermal inertia, ensures rapid achievement of optimal indoor comfort while minimizing energy consumption. New or renovated buildings undergoing deep envelope retrofits typically have low heating loads. Therefore, an efficient and responsive heating system is required to prevent overheating once comfort conditions are reached. Low thermal inertia systems effectively meet these requirements.
Additionally, radiant heating and cooling systems provide optimal indoor comfort. Total heat transfer within a room combines convective and radiant heat exchange affecting all surfaces and occupants. Radiant systems make radiant heat transfer dominant over convection, ensuring uniform air temperature. This uniformity prevents unwanted convective currents that typically circulate dust in traditionally heated spaces. Furthermore, the small temperature difference between floor and room reduces natural convective effects, lowering dust and bacteria circulation.
These systems operate at low temperature differences, typically 35 °C in winter and 18 °C in summer, making them ideal for pairing with high-efficiency generators such as heat pumps, thus improving generation efficiency and overall system performance compared to high-temperature systems.
Key low-thermal-inertia radiant solutions include:
• Gypsum Board Ceiling Radiant Panels [2]:
Low-inertia systems installed directly in the suspended ceiling, integrating low-temperature water pipes within gypsum or composite panels. Benefits include:
Homogeneous thermal comfort across all building spaces, eliminating upward convective currents and temperature stratification;
Rapid response to internal temperature changes due to lightweight construction, reducing activation/deactivation times;
Use of low supply temperatures (30–40°C for heating, 16–18°C for cooling), reducing losses, energy consumption, and greenhouse gas emissions;
Integration within the ceiling allows for aesthetic and functional solutions, including lighting or equipment integration;
Modular design enables flexible and fast interventions during renovation or retrofits;
Enhanced acoustic comfort depending on panel selection.
• Low-Profile, Low-Inertia Underfloor Systems [3],[4]:
These systems use modular insulating panels and thin tubing, covered by a self-leveling screed (anhydrite or sand-cement) with a total thickness of 20–30 mm. Advantages include:
Optimal thermal comfort similar to ceiling radiant panels, ensuring healthy indoor environments;
Use of low-temperature water (approx. 15 °C cooling, 35 °C heating), reducing energy consumption;
Reduced floor load compared to high-inertia systems (approx. 40 kg/m² less).
During cooling seasons, underfloor radiant systems can be integrated with mechanical ventilation equipped with dehumidification to control indoor humidity, enhancing comfort and preventing surface condensation.
The adoption and installation of low-thermal-inertia radiant systems are regulated by specific technical standards ensuring efficiency, safety, and compliance with Italian and European regulations on energy efficiency and sustainability:
UNI EN 1264:2021: Water-based radiant systems for integrated heating and cooling in structures [5]. Defines performance requirements for radiant systems, including low-inertia types.
UNI EN ISO 11855:2021: Design of the built environment – integrated radiant heating and cooling systems [6]. Provides a comprehensive framework for design, sizing, and installation of low-inertia systems.
UNI 11944:2024: Screeds for flooring – design, installation, and verification criteria [7]. For the first time, considers the entire floor system stratigraphy, including screed, underlayment, heating/cooling systems, acoustic/thermal insulation layers, and vapor barriers. Classifies radiant systems based on screed characteristics:
Traditional radiant system: screed ≥ 30 mm above pipes;
Reduced-thickness traditional radiant system: 15–30 mm above pipes;
Low-thermal-inertia radiant system: ≤ 15 mm above pipes.
[1] European Union. 2024. Directive 2024/1275/EU of The European Parliament and of the Council of 15 March 2024 on the energy performance of buildings (recast). Official Journal of the European Union. Brussels.
[2] Giacomini. Ceiling Radiant Panels: Why Choose Them. Giacomini, 15 July 2021. URL: https://it.giacomini.com/news/pannelli-radianti-soffitto-perche-sceglierli
[3] Giacomini. Low Thermal Inertia Underfloor Radiant System: What You Need to Know. Giacomini Academy. URL: https://it.giacomini.com/academy/approfondimenti-tecnici/sistema-a-pavimento-radiante-a-bassa-inerzia-termica-cosa-ce-da-sapere
[4] Pastore, Matteo. Low Thermal Inertia Underfloor Radiant System: What You Need to Know. Ingenio Web, 22 March 2021. URL: https://www.ingenio-web.it/articoli/sistema-a-pavimento-radiante-a-bassa-inerzia-termica-cosa-c-e-da-sapere/
[5] UNI EN 1264:2021. Water-based radiant systems for integrated heating and cooling in structures. UNI, Milan, 2021.
[6] UNI EN ISO 11855:2021. Design of the built environment – integrated radiant heating and cooling systems. UNI, Milan, 2021.
[7] UNI 11944:2024. Screeds for flooring – design, installation, and verification criteria. UNI, Milan, 2024.
