On 06/12/2016 22:37, Andrew Mawson wrote:

When we did up the house and holiday cottages, I bought rolls of garden
type green nylon netting off ebay, and stapled it to the joists, laying
insulation batts suspended by it.

Andrew

I did similar ... just put the aluminium reflector foil under the pipes
(industrial bacofoil) then 150mm rockwool pressed in place .. and used
a lattice of nylon cord zig zagging from joist to joist ... stapling in
place on the joists.

By having rockwool slightly oversize it self supported itself ... cord
just stops sag over time.