6 CONVECTIVE HEAT OUTPUT

When heat is given off some of it is lost to the structure
and contents by radiation from the hot gas plume. If the roof
reservoir compartments exceed 2000m² in plan area then
consideration should also be given to the radiative and
conductive losses from the established smoke layer to the
roof structure (see Appendix 2 Reference 6).
The convective heat output of the fire is determined by
applying a correction factor to the total heat output
(see Section 5).
Various technical papers give differing values for the heat
loss correction factor. Further research is desirable but, in
the meantime, a 20 percent loss should be applied. For roof
areas greater than the recommended smoke compartment size,
calculations of the heat lost from the smoke layer should be
provided to support the increase in recommended reservoir
size such as a Newtonian heat transfer coefficient method
(see Appendix 2 Reference 7).