Underfloor ventilation to enhance thermal comfort

Presented toThe Green Buildings Congress Hyderabad, September 2009

Author: Glan Blake Thomas C Eng MCIBSE

Member British Council for Offices International Committee

Improved Construction standards offerimproved staff performance

3

The British Council for Offices champions high quality office

space in the UK

Efficient office spaces incorporate flexible working and practical

meeting areas

Greater efficiency is a major driver in European office building design

Raised floors are commonplace in office buildings

The evolution of underfloor air distribution

Underfloor Air Distribution is widely accepted

Indoor Air Quality is high

Benefits of going underfloor

From this..... To this.....

Using the underfloor void for air distribution may be a useful tool in reducing the height of a building

Height saving in new buildings reduces cost in both fiscal terms and embodied energy

consumption

This 87 storey, Cheung Kong building in Hong Kong uses underfloor air distribution. Over 35m (10 floors) was saved in the height of construction whilst still retaining the same ceiling height as in the original design using overhead air distribution.

Thermal gain and therefore cooling loads are dramatically reduced

– Energy costs(Power, Water, Gas etc.)

85%

Total Costsafter 30 Years

15%

100%

Costs

TimeOperation

– Building operation costs

Investment

Construction

– Maintenance costs(preventive, planned costs)

– Facelifting, Investment

15%

– Maintenance costs(corrective, not planned costs)

– Costs for Construction

up to 60%

Life-cycle cost Complex Buildings

Reconfiguration is easy and less wasteful

Systems may be detached entirely from the building fabric

So....how does it work? Underfloor air may be supplied either centrally or on a zonal basis

The Center, Hong Kong

Zonal Air Handling Units Central Plant

Underfloor supply is often extracted at high level

Floor return is an option too

Air is filtered and cleaned using a variety of methods

Air may be introduced by fan power so reducing underfloor pressures

TEMPERATURE

VELOCITY

Air may be introduced very locally

Or very commonly by Displacement Swirl Grilles

VAV systems are popular in Europe

The next generation of VAV

IAQ in Underfloor Systems

Underfloor supply/high level return High level supply/high level return

Study of IAQ in Underfloor & Overhead Systems

04080

120160

Particles per cubic metre (millions)

Shin-Ichi Tanabe is a professor in the Department of Architecture, Waseda University, Tokyo, Japan.

Hong Kong University study of Underfloor Air Desired Control Over Office Environment

6%

23%

67%

4%

No Control

Little Control

Some Control

Complete Control

Swedish Clinic for Occupational Medicine

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Underfloor air:• may be used in a wide variety of applications for cooling and/or heating. • is suitable for both new build and refurbishment applications• is suitable for floor voids as low as 150mm• offers increased headroom in refurbishments• saves up to 15% on the height of new buildings• allows freedom in design through the absence of overhead services• saves 90% in churn costs over ceiling systems through ease of reconfiguration• offers energy savings through zonal control, reduced fan power and free

cooling• may be used with re-usable energy applications• can assist in achieving improved LEED or BREEAM scores

• OPTIMISES INDOOR CLIMATE CONDITIONS SO AS TO MAXIMISE PRODUCTIVITY

As Engineers, we must not stay quiet, we must search for new ways and we must listen to

others

Remember, the World’s

resources are not inherited

from our ancestors, but

borrowed from our childrenwww.flexiblespace.com

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