Steam cleaning is one of the best ways to clean a roof effectively. Not only does it provide instant results, but it is an eco-friendly alternative to chemically cleaning a roof with biocides. As water temperature is so high, steam will kill a variety of living organisms such as algae, moss, lichen, mould, and mildew. Steam will not only kill the organism, but also remove its root system. Just like uprooting a weed is more effective than simply snipping the top of it off, steam cleaning will effectively kill and remove moss.