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CPD Programme
CPD Programme
The CIBSE Journal CPD Programme programme is free and can be used by any
Members of the Chartered Institution of reader. It is organised jointly by CIBSE Journal
Building Services Engineers (CIBSE) and other and London South Bank University, and will
professional bodies are required to maintain help you to meet CIBSE’s requirement for
their professional competence throughout CPD. It will equally assist members of other
their careers. Continuing professional institutions, who should record CPD activities
development (CPD) means the systematic in accordance with their institution’s guidance.
maintenance, improvement and broadening Simply study the module and complete the
of your knowledge and skills, and is therefore questionnaire on the final page, following the
a long-term commitment to enhancing your instructions for its submission. Modules will
competence. CPD is a requirement of both remain available online at www.cibsejournal.
CIBSE and the Register of the Engineering com/cpd while the information they contain
Council (UK). remains current. You can also undertake the
CIBSE Journal is pleased to offer this questionnaire online, and receive your results
module in its CPD programme. The back by return email.
Sensing the need for demand
controlled ventilation
The successful monitoring and control of the quality of room air is becoming
increasingly important – particularly as the application of novel building
techniques and materials coincide with improved awareness of their effects
on comfort and health. This CPD considers the rationale behind demand
controlled ventilation systems and the methods used to feed back the
demand for that ventilation
D
emand controlled ventilation through the use of both intelligent sensors cited by Terry Wyatt at the recent CIBSE
(DCV) is a strategy that attempts and purpose made air volume control conference
[2],
relied on the teacher making
to reduce the energy used dampers (see picture, right). This article will a subjective decision that there was a need
by ventilation systems while particularly consider the need for additional ventilation
maintaining required levels of indoor air for DCV and the sensors that and then opening a window.
quality (IAQ). Since many buildings will are used to feedback some Similarly, basic mechanical
regularly operate at occupancies below measure of air quality. ventilation systems are
the design maximum, the requirement to controlled by occupants
provide ventilation will also be frequently Demand controlled simply switching them as
less than the peak design value. Modern ventilation circumstances demand.
implementations of DCV have overcome Historically, buildings relied However, automation allows
earlier problems that arose from on manual regulation to
Figure 1 - Specialist DCV
the monitoring of a condition
inappropriate control and excessively ensure adequate ventilation. In
Volume Control Damper
and the variation of ventilation
high design system pressure drops. The its most basic form, this would strategy to satisfy some pre-
resulting installations can show significant be by the occupant sensing a shift from set condition that attempts to emulate the
energy savings resulting most significantly conditions of comfort (predominantly human controller whilst, in many cases,
from reduced fan power and reductions characterised by people as ‘temperature’ minimising the use of energy.
in the heating of fresh air. Digital control or ‘humidity’) and opening, or closing a Temperature and humidity are the
has enabled systems that, as well as being window
[1]
. So, for example, the Victorian and principal measured and controlled variables
energy efficient, maintain low noise levels Edwardian classrooms (picture, over page) in HVAC for traditional systems based on a >
www.cibsejournal.com September 2009 CIBSE Journal 59
CIBSEsep09 pp59-62 cpd.indd 59 8/20/09 7:09:28 PM
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