I am trying to figure out whether one should take into account the cooling power of the surfaces being replaced. The figure of 80-120 W/m2 for air conditioning

I am trying to figure out whether one should take into account the cooling power of the surfaces being replaced. The figure of 80-120 W/m2 for air conditioning is presumably based on conventional building materials, which have negative cooling power. In the paper, the figure of 40 W/m2 seems to be the net cooling power, which is defined in equation 1 as being the power radiated away minus various inflows of heat: radiatively, from the atmosphere; radiatively, from the sun; and by conduction and convection. As far as I can see, these corrections are all for this particular surface, not the surface it might be replacing. These will not, in general, be the same, and, given that this new surface is both highly reflective and vacuum-insulated, I would guess that its values for these properties are lower than the conventional building materials on which the a/c rule-of-thumb is based. Nevertheless, I doubt that replacing the entire roof with this material would be sufficient cooling, on its own, in the Australian case, and I agree that this would not likely be a straightforward retrofit, to say the least!