Classroom Environment:Layout 1 01/07/2009 16:15 Page 70
the classroom environment
Turning down the heat
Recent programmes to improve the quality and energy performance of educational
buildings have brought about significant changes to the built environment. However, the
approach to selecting heat emitters in the classroom hasn’t always kept pace.
Consequently, many teaching spaces have heating systems that fail to maintain the
required comfort levels, argues DAVID SHUTTLEWORTH.
F
OR EXAMPLE, the move to consumed is insignificant compared to the
condensing boilers favours lower savings that can be achieved with a highly
water temperatures (compared to responsive system. However, where heating
traditional boilers) if maximum condensing systems based on natural convection are
is to be achieved. Similarly, many more preferred; perimeter, trench or individual
local authorities are encouraging the use natural convectors with low water volume
of heat pumps, again using lower flow and heating elements and local controls will
return temperatures (around 50°C/45°C) still provide rapid response, improved
to improve their efficiency in cold comfort and energy savings.
weather. All of this means that the
heating in teaching and other spaces Breathing space
needs to be optimised for lower In terms of maintaining a comfortable
temperature hot water than would have built environment, it is equally important
been the case just a few years ago. to consider fresh air requirements – and
In parallel, better insulated buildings with tighter buildings there can be less
reduce heat losses, while the thermal emphasis on natural ventilation. Again, it
mass of the building fabric has remained is important to be able to respond to
almost constant; leading to protracted changes in occupancy to minimise energy
The key is to respond quickly to changes. warm-up periods at full load. Once the consumption. Fan convectors fitted with
spaces have reached the design a fresh air inlet can be used as a small air
temperature it’s important the heating handling unit, ensuring that tempered
system is sufficiently responsive to fresh air is introduced to the space at
match the heat loss and accommodate the appropriate volumes.
any internal heat gains with as little In the case of perimeter heating,
overshoot, or undershoot, as possible, specially developed vents with motorised
thus conserving energy.
While the first consideration for
accommodating lower water
a teaching space with
temperatures is often underfloor
heating, the fact is that underfloor
variable occupancy
heating is inherently slow to respond to
can experience
changes. As a result, a teaching or
meeting space with variable occupancy
dramatic temperature
can experience dramatic temperature
fluctuation during the day, exacerbated fluctuation during
by the changing orientation of the sun.
the day
Response
In contrast, fan convectors offer a fast dampers and attenuators can be fitted
response, taking advantage of internal into the wall of the building, allowing fresh
and solar heat gains to reduce energy air to be drawn across the high level
consumption. Fan convectors have been heating elements using the ‘stack effect’
designed to work with a wide range of or extract fans. In both cases the fresh
water temperatures, and can also be air volumes can be adjusted anywhere
supplied in low surface temperature between recirculation and 100% fresh air
versions (not exceeding 43°C surface and, where required, linked to carbon
temperatures) where this is required by dioxide sensors to provide demand-
local guidelines. controlled ventilation.
Nevertheless, it is a fact that some local David Shuttleworth is technical director
authorities have chosen to move away at Dunham-Bush.
from fan assisted heating because of
perceived energy disadvantages – though
www.dunham-bush.co.uk
I would argue that the motor power
70 edbmagazine.co.uk
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