Overview
EN ISO 11855-2:2021/A1:2023 is an amendment to Part 2 of the ISO 11855 series: Building environment design - Embedded radiant heating and cooling systems - Determination of the design heating and cooling capacity. Issued by CEN and prepared by ISO/TC 205 with CEN/TC 228 collaboration, this amendment updates calculation methods, system classifications, symbols and selection criteria used to determine design heating and cooling capacity for embedded radiant systems (floor, wall, ceiling).
Key Topics
- Scope and status: Amendment A1 modifies EN ISO 11855-2:2021 and was approved by CEN in 2023 for national adoption by mid‑2024.
- System classification: Introduces five simplified system types (I–V):
- Type I: pipes in a thermal diffusion layer
- Type II: pipes in insulation with a conduction layer
- Type III: capillary tubes in a diffusion layer
- Type IV: pipes with reflection layer and air gap to covering
- Type V: pipes embedded directly in structural mass (TABS)
- Updated figures and symbols: Figures 2–6 and Table 1 (symbols) revised to reflect new system definitions and layer descriptions (e.g., Td thermal diffusion layer, Tc conduction layer, Tr thermal reflection layer).
- Selection criteria and boundary conditions: Table 2/A.1 provides clear numeric criteria for choosing simplified calculation methods using parameters such as pipe spacing (W), layer thickness (s), pipe diameter (d), material thermal conductivity (λ) and ratios like s/λ. Example thresholds from the amendment include conditions like T ≥ 0.050 m, 0.008 m ≤ d ≤ 0.03 m, and 0.01 m ≤ s/λ ≤ 0.18 where applicable.
- Calculation methods: Annex A (simplified characteristic curves) and Annex B (general resistance / thermal network concept) were amended to cover the expanded system types and to adjust characteristic-curve calculations and limits of heat flux for embedded heating/cooling elements.
Applications
- Design and sizing of embedded radiant heating and cooling systems (radiant floor heating, wall/ceiling panels, TABS, capillary tube systems).
- Performance verification for HVAC design documentation and energy compliance.
- System selection guidance: helps designers choose the correct simplified or general calculation method based on physical construction and boundary conditions.
- Manufacturer and product development: informs product specifications for embedded piping, diffusion layers, insulation and conductive elements.
Who should use this standard
- HVAC engineers and building services designers
- Energy consultants and sustainability assessors
- Architects involved in integrated building HVAC solutions
- Manufacturers of radiant heating/cooling components and control systems
- National standards bodies and compliance officers
Related standards
- Other parts of the ISO 11855 series (refer to the ISO catalogue for the full list). National adoptions and language versions are managed by CEN members.
Keywords: EN ISO 11855-2, embedded radiant heating and cooling, design heating capacity, design cooling capacity, radiant floor heating, TABS, capillary tube systems, thermal diffusion layer.
