Quote -  Thanks Kevin, so am I correct to assume that the material name on a portal in the .lxo file must be "portal" to have luxrender recognise it as a Portal?

That been said, portals won't help you with your Warehouse scene, since it's an exterior.
Portals are useful for limiting the directions the engine will be looking for light sources in; In this case the only direction there is no light is the ground (the sky is an area light)...

(If you're just talking generally, disregard)