Loft insulation, if installed properly, should not need replacing at all. That's of course applies for new builds where you can plan your insulation install. For existing homes, a few more factors must be considered, what type of insulation there is, is it affected by damp and mould, how old the building is etc. To answer the question, I'd say you will need a loft survey to determine any further actions.I would recommend researching different materials used in the UK for insulation purposes and then decide on the best option. Spray foam insulation is fairly new to the UK market but tried and tested across Canada. It outperforms other types like fiberglass or mineral wool. Please visit newbielink:http://www.homelogic.co.uk [nonactive] for more information on this.