Tuesday, 15 September 2009

Biased Carbon Trust - misleading some Industrial & Commercial energy users.

Carbon Trust's Promotional Materials - lack of impartiality:

 ECA766 - Radiant heaters vs ECA767 - Warm air heaters


As a company funded by the Taxpayer it should have no remit to be biased towards one particular technology whilst simultaneously discriminating against a competing technology in the same field [Industrial and Commercial ‘large, single open space’ heating]. As it highlights some benefits of Radiants vs Warm Air in ECA766, it has an equal obligation to highlight the many benefits of Warm Air vs Radiants in ECA767.


1        The Carbon Trust's propaganda in ECA766 ignores the fact that modern, well insulated buildings can, as a rule of thumb, be heated and ventilated using less energy with a warm-air system than with a radiant system. The following benefits should be mentioned in ECA767.

1.1  Total appliance input is lower with warm air heaters.

1.2  Generally, fewer warm air heaters can provide the required comfort. (Less energy used in their manufacture and subsequent installation). Their illustration below confirms that multiple radiant sources are necessary to avoid asymmetrical radiant discomfort.

1.3  Modern buildings are generally designed not to have air-infiltration. Most warm air heaters can be installed as room-sealed, requiring no additional (cold-air entraining) ventilation for combustion.

1.4  However, to comply with BS 6896:2005 Clause buildings having radiant heaters must have additional (cold-air entraining) ventilation for combustion at both high and low level. [Unless every burner has combustion-air ducted from outside.]

1.5  Buildings requiring heating & ventilation need have only a warm air system. Radiant systems are incapable of ventilating, so an additional system, with its own carbon footprint, has to be added.

1.6  Warm-air heaters can recycle & recirculate some of the “free” heat emissions from people, lighting, processes and solar-gain. Radiant heaters are incapable of recycling their own substantial upward emissions (>40%) or other heat emissions.

1.7  Warm air heaters maintain a high efficiency throughout their life. Reflectors of radiant tubes tarnish relatively rapidly, and so their downward radiant efficiency diminishes.

1.8  Warm-air heaters may be supplied with 2-stage or modulating burner control to further reduce energy consumption. It is impractical to fit modulating burners on a radiant heater; and, a 2-stage burner is suitable only for a (flueless) plaque heater that can have ½ its plaques at 100% (to maintain maximum emissivity) plus the other ½ at 0% (i.e. rather than all at 50%). But being flueless requires even greater cold-air ventilation.

1.9  Warm air heaters are available as continually-condensing appliances with a net thermal efficiency of up to 104%. Radiant heaters have a net thermal efficiency of only just above 86%.


2. The illustration on P2 of ECA766 Radiant Heaters deliberately misleads readers into believing all the heat from a radiant heater is projected downwards. 

The downward radiant efficiency of a radiant tube is only about 60%, so nearly 40% rises.


 That 40% of wasted, irrecoverable heat must also be indicated on their illustration.


The Carbon Trust should therefore amend one or both of their ECA766 - Radiant heaters and ECA767 - Warm air heaters on-line pdfs to better reflect the true comparisons, and actually assist users to make an informed decision based upon facts, so that energy consumption & carbon emissions can be minimised.