Building a better world

11/6/2002

Low-cost cooling with displacement ventilation

BRE has completed a project to determine whether displacement ventilation can be an effective cooling method that maximises the potential for using ambient air for low-cost, energy-efficient cooling.

The limited cooling capacity of most current displacement ventilation systems restricts their use to buildings with relatively low heat gains, or where an additional cooling system is provided. This project investigated the potential to improve displacement ventilation so that it can be used as a standalone method of cooling a wider range of buildings – and to maximise the use of ambient air as a cooling source.

Findings showed that displacement ventilation on its own is able to deal with far higher heat loads than usually thought.

Tests on a number of diffusers showed that conventional wall diffusers and prototype innovative fabric diffusers have the greatest potential for providing the higher air volumetric supply rates needed to allow displacement ventilation systems to deal with higher heat loads.

An Information Paper (IP 6/02) summarising the project’s findings and providing information on the application of displacement ventilation is now available (from www.BREbookshop.com). As well as giving advice to manufacturers and building services engineers, it provides outline guidance for architects and designers on the use of displacement ventilation for energy-efficient cooling.

The project was supported by the DTI’s Partners in Innovation research programme and industry sponsors, including Arup Research and Development, CIBSE, IPS Ventilation Ltd, Gilberts (Blackpool) Ltd, Halton Products Ltd, Hoare Lea, Oscar Faber, Troup Bywaters & Anders, Trox (UK) Ltd and Waterloo Air Management plc.

Displacement ventilation
A displacement ventilation system works by supplying fresh, cool air into a room at a low level. The fresh air slowly spreads along the floor forming a reservoir of cool fresh air near the floor and displaces warmer air above. Thermal plumes created by room occupants and other heat sources draw air from this reservoir. Any pollutants emitted by the heat sources will be carried upwards into an upper zone of warm contaminated air near the ceiling and the air extract points. Fresh, cool air therefore continually replaces the warm contaminated air.

David Butler on 01923 664300 or e-mail butlerd@bre.co.uk.