- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 25 Sep 2020
Plenum ventilation in buildings
Plenums are air compartments or chambers that are sometimes found in buildings, either above suspended ceilings, in the gap between the ceiling and the floor slab, or below raised floors in the gap between the raised floor and the floor slab. They form part of the ventilation system for the building.
They may be supply or return plenum, and may serve either an entire building, or a specific zone in a building. Supply plenum supply ventilation air to the occupied space, whilst return air is generally extracted through ductwork. Conversely, in return plenum the air is generally ducted to the space, whilst the return air is extracted through the plenum.
Underfloor air distribution (UFAD) uses the underfloor plenum beneath a raised floor to provide ventilation air through floor diffusers directly to the occupied zone. The air spreads across the floor forming a reservoir of fresh, cool air. Any sources of heat (such as people or computers) generate a thermal plume lifting contaminated air to high level where it can be removed from the space. See Underfloor air distribution for more information.
Plenum can give good flexibility for the layout of buildings. However, they can provide a space within which fire can spread, particularly because of the air supply they offer, and so they may be required to include fire and smoke detection, and potentially combustible material (such as cables) may be controlled. They can also create a pathway for the transmission of sound between separate spaces.
 Find out more
 Related articles on Designing Buildings Wiki
- Active thermal mass.
- Air handling unit.
- Chilled beam.
- CIBSE Case Study Olympic Velodrome.
- CIBSE Case Study Ortus Learning and Events Centre.
- Ground preconditioning of supply air.
- Herringbone strut.
- Floating floor.
- Floor plenum airtightness.
- Mechanical ventilation.
- Night time purging.
- Raised floor.
- Sprung floor.
- Suspended ceiling.
- Thermal labyrinth.
- Thermal mass.
- Underfloor air distribution
Featured articles and news
BSRIA examines factors driving the industry.
Ensuring designs are developed, validated and can be effectively implemented.
The Homebuyer Survey most suitable for newer homes or simple properties.
Health and safety practices for body and mind.
28 leading bodies set out their vision for the future.
Chancellor announces latest Winter Support packages.
Tapping technology to boost infrastructure and create jobs.
4 ways to ensure certificates are valid.
White elephant construction projects.
How Paul Williams bent over backwards to overcome racial barriers.
Organisation revises actions around dealing with COVID-19.
CIOB, NFCC, RIBA, RICS call for changes ahead of Building Safety Bill.
Developments in the Future Homes Standard.
An American chimney feature with a colourful past.