Non felted roof

[orackhan02]

Hey just want some advice I have just bought my first house and the roof is not felted.
The roof is in fairly good condition only issue is that there seems to be a lot of dirt in the loft, it may of build up over time and the last owner probably didn't go up there much.
It is already insulated but I plan to but in more loft insulation and then put loft Pannals down so I can store stuff in it but I'm worried about it becoming dirty again and damaging my stuff.
Is there anything I can put on the roof beams that would stop the dirt coming in? That wouldn't damage the roof or house?

I've been told that i could staple membrane to the roof beams? And is so what kind or brand should I use

Big thanks in advance

 

[Wayners]

I've seen correx board stapled to the inside of timbers then tape joints. I'd use correx tape.
. Condensation is the worry.

Maybe membrane is the answer with battens to hold

 

[Dereekoo]

Breathable membrane would keep the dust out and avoid any condensation issues, Membrane may clag up with dust over the years but that should be a long way off