Is it worth replacing this loft insulation?

[HannibalSmith100]

I had to take up some of the boards in the loft to gain access to a light fitting and noticed that the majority of the insulation already fitted is only filling 1/3 - 1/2 of the cavity space. Is it worth buying new insulation to fully fill the cavities? I would need 100mm insulation rolls and would cost less than £100 in total for the whole floor space.

If I went ahead, should I keep the old insulation in place for a bit of extra insulation, or should I just get rid of the old stuff?

 

[Old Salt]

I would add some new stuff on top, every little helps.

 

[HannibalSmith100]

Thanks, I'll go ahead and add more. I think the old stuff has either collapsed over time or just wasn't very thick to start with. The insulation on the left of the photo fills the cavity so I'll aim to do the same all over.