Can you put hardbord on fibreboard for better insulation?

[Chlorinated]

I currently have floorboards with 6mm fibreboard on top with laminate on top of that.

I want to change to vinyl flooring.

1. Can I keep the fibreboard, put hardboard on top and then put the vinyl. Will this work and will it create better insulation then hardboard and vinyl only?

2. Usually hardboard isnt recommended for vinyl, i believe this is because the underlying floorboards will cause the hardboard to shoot up.
however since the floorbaords have both fibreboard and hardboard to even everything out, is it ok to use hardboard for vinyl in this case?

Thanks

 

[PrenticeBoyofDerry]

I wouldn't rely on hardboard, you really want to ply it.
Any material used will offer some resistance to heat loss, so can only be an improvement.