Overview
ISO 7615-1:2024 - Energy performance of building systems - Underfloor air distribution systems - Part 1: General overview provides a structured, normative introduction to underfloor air distribution (UFAD) systems. The standard defines terminology, symbols and subscripts, technical specifications and key performance considerations for UFAD installations that use an underfloor plenum to supply conditioned air into the occupied space. It is a Part 1 general overview and is applicable to all UFAD configurations (raised floor, zone AHU, underfloor plenum, underfloor air diffusers). It does not apply to ceiling-based diffusers, AHUs alone, or displacement ventilation systems.
Key topics and technical requirements
The document organizes essential UFAD knowledge into clear elements:
- Terms and definitions - canonical definitions for UFAD, raised floor, underfloor plenum, diffusers, thermal plume, space air stratification, thermal decay, pressurized/neutral/ducted plenum, stratification height, occupied zones, and underfloor terminal units.
- Symbols and subscripts - standardized notation for airflow (Q), temperature (T), stratification parameters, buoyancy flux and other quantities used in UFAD performance assessment.
- Technical specifications - descriptions of major plenum design approaches and typical parameters:
- Plenum approaches: pressurized, neutral, combined (pressurized + neutral), and ducted plenum.
- Typical plenum heights: commonly 0.15 m to 0.45 m (from structural slab to raised floor).
- Diffuser types: passive swirl, displacement ventilation diffusers, variable-area (VAV) passive diffusers, linear bar grilles, fan-powered VAV diffusers, and air-permeable carpet tile systems.
- Performance considerations: space air stratification, thermal decay of supply air through the plenum, underfloor plenum air leakage, acoustic performance, occupant comfort, and maintenance of conformity.
- Informative annexes: Annex A–D provide detailed descriptions of plenum approaches, diffusers, perimeter terminal units, and UFAD design examples.
Normative references include ISO 7730 (thermal comfort), ISO 13731 (vocabulary), and ISO 16818 (HVAC test procedures).
Practical applications and users
ISO 7615-1:2024 is valuable for:
- HVAC engineers and system designers specifying UFAD systems and selecting plenum/diffuser strategies.
- Building energy modelers assessing energy performance impacts of stratification and thermal decay.
- Architects and façade engineers coordinating raised-floor geometry with building envelopes and perimeter zones.
- Facility managers and commissioning teams using the standard to inform maintenance and conformity checks.
- Manufacturers and suppliers of raised-floor systems, diffusers and underfloor terminal units.
Keywords: ISO 7615-1:2024, underfloor air distribution, UFAD, underfloor plenum, raised floor, diffusers, energy performance, HVAC design.
Related standards
- ISO 7730 - Ergonomics of the thermal environment (PMV/PPD)
- ISO 13731 - Thermal environment vocabulary and symbols
- ISO 16818 - Building environment design - HVAC test procedures
For implementation details and design examples consult the informative annexes and the wider ISO 7615 series.