My house was built with a flat roof. The previous owners had pitched
roof constructed on top of it so that when you enter the roof space
you can walk anywhere on the original bitumen & gravel finish. We
have broken through the old roof to fit ventilation trunking for a
bathroom extractor and I see that the old roof is made up of a
boarding material about 50-75 mms thick which seems to have been made
with a straw-like material.

I don't think that the old roof gives much insulation and it may be a
good idea to upgrade it.

Could I get a cavity wall insulation co. to blow some sort of flaked
material into the void above the bedroom ceilings and below the old
roof? How might they do it?
Is there any way that this could be a diy job?

Any experience/ideas out there?

EP