An indirect evaporative cooling system for cooling a space adjacent to or containing an ablution bay is described. The indirect evaporative cooling system includes a greywater source from the ablution bay and evaporative cooler apparatus located above the space to be cooled in a dome shaped housing. The evaporative cooler apparatus includes a wet channel, at least one spray nozzle, and a dry channel. The at least one spray nozzle is located at the top of the evaporative cooler apparatus and is fluidly connected to the greywater source and the wet channel. The wet channel is located directly above the dry channel. A first side of the dry channel is connected to a first opening with a fan and outside air.