Heat gains assumption in CIBSE AM10

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Hello All

I want to know more on the assumption of heat gains for natural ventilation of buildings, as set by the CIBSE AM10. This flowchart is referred to by LEED, so I guess anyone who works on natural ventilation for LEED should know this flowchart.

As seen in the flowchart, up at the top, there is a limit for a total heat gains of 30-40 W/m2, if we want to use natural ventilation for our building. Above that, we need to consider some sort of mechanical ventilation. My question is: what is the assumption for this value? There should be an assumption of indoor air temperature to be achieved by this heat gain limit. Or at least a certain deltaT between indoor and outdoor temp.

I have tried to look for the sources of this limit, to no avail. If anybody can point me to the right direction, that would be great.

I am working on a naturally ventilated factory with a much more lenient limit of space temperature compared to a typical office space. With the higher set of indoor temperatures, the limit of 30-40 W/m2 does not make sense.

Any comment to this point would also be very welcome.

Thanks.