I was in the loft to do top up insulation yesterday. Underneath the existing insulation in between beams (not on them, they seem fine) is a white granule/crystalline salt like substance (like little tiny irregular balls). It looks like salt crystals but is very light. It's thicker in some places than others. After researching on the internet I think it may be a form of loose insulation filler maybe used prior to the 1st layer of loft insullation roll being put in. I have pictures.
Does this seem plausible? Is there any other thing that could cause a build up of this kind i.e. it has not been put down by someone but has accumulated after the loft insulation was put there? I'm just wondering if it may be harmful or why it may be there? Should I continue with the top up insulation?