retrofit air tightness in attic space

Robbie71

Bungalow with a converted attic ,
ref The triangular crawl space behind the bedroom walls
the bedroom walls have mineral wool insulation which is sometimes exposed to a breeze in this crawl space.
I am wondering if is worth putting a membrane over the insulation to prevent windchill.
I can only go from the floor to the pitch of the roof but think it may be worth doing ??
it wont be a perfect airtight fit but surely it would help reduce the heat being pulled out of the mineral wool.

Any opinions/comments would be appreciated

Do-more

From what I am lead to believe mineral wool looses half of it's effective u value if it has air moving through it.

With mineral wool laid on the flat in an attic something as simple as laying building paper across the top of it (and better still between each layer if it is installed in layers) can be effective in reducing the loss of u value due to air currents, so in your case even if you will not have a fully airtight seal the reduction in air blowing through the insulation should make the job well worth doing.