Heating Industrial and commercial 1
Changes to buildings can > making them the first choice for new build. However, point faster than a poorly insulated space for the same
affect system performance. retrofitted and refurbishment products will still favour heat input. According to some, this also has significant
radiators.’ implications for the specification of heat generation
Barker doesn’t see an issue with radiator sizes, and emitting equipment.
even in older properties: ‘All sorts of things may have Dave Shuttleworth, technical director of fan
changed from when the heating system was initially convector supplier Dunham-Bush, explains: ‘‘Heat
installed – for example, double glazing, new insulation input is traditionally calculated to match the steady state
within the building, and so on. You may think that the heat loss at a prescribed external minimum condition.
heat emitters may not therefore be adequate. Equally Because of improved insulation and air tightness,
though, the consultant may find that the system is an these values are now significantly lower. But, the
older one that was sized by “rule of thumb” where an thermal mass of the space and contents are relatively
estimate was made and another, say, 20 per cent was unchanged and this will lead to inefficient protracted
added on for good measure, so they were oversized warm-up periods, unless additional allowance is made
in the first place. Therefore, they might well be to the heat input.’
adequate for a heating system operating at lower Shuttleworth believes that, if the heat input to
temperatures.’ the space is increased, then it is essential to prevent
In fact, low flow rates offer distinct advantages overshoot and this can only be achieved by good control
in terms of economy and energy saving – after all, of heat emitters. ‘At the same time,’ he adds, ‘other
less heat needed to be generated means less energy factors such as variable occupancy and changing solar
expended and therefore more energy saved. heat gains through the day will have a more profound
And there are other benefits, as Mills points out: impact on space temperatures in well-insulated space –
The problem
‘Lower flow rates mean you can use smaller-sized this requires good local control of the heat emitters.
lies in ensuring
pumps and the energy used by these is a prime focus ‘The heat emitters, therefore, need to provide rapid
in respect of energy saving at the moment. Also, if the warm-up of the space when initially switched on, and
that the chosen pipes are sized correctly, you get lower velocities and then be highly responsive to fluctuating internal heat
heat emitters are
therefore less noise in the system.’ gains and heat losses once the design temperature has
sized correctly
Better-insulated buildings have also had a marked been reached – with as little overshoot, or undershoot,
impact on the design of heating systems because a as possible.’
– John Bailey tightly-insulated and airtight space will reach its set Consequently, he says, the best solution for many >
52 CIBSE Journal February 2010
www.cibsejournal.com
CIBSEfeb10 pp50-55 feature_Heating.indd 52 29/1/10 14:31:30
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