Hi, when we first bought out house thirteen years ago ( an end house of four built in 1936 in north London. u.k.) I went up into the roof space one winter; and found the whole inside to be covered in a thin layer of snow. ( There was quite a high wind and it had blown the snow inside between the tile gaps ).
To remedy this problem i bought a roll of special roof plastic, (cannot remember the name, but it is made for this purpose and has an inbuilt lattice of nylon string for added strength ) which i laid up close to the tiles and stapled to each side of the wood rafters. This now keeps the snow out, but everything still gets covered in a thin layer of dust and grime.
We would like to further seal the roof to keep out this dust, but this does not have to be too elaborate, since the roof space is not a living space, but more of a storage space. Also i have laid rock wool insulation in the floor space so we do not need any extensive extra insulation properties on this project.
what i thought would be a relatively easy option is to get some of those building sheets of white polystrene type material and cut them into strips and nail them to the inside face of the roof rafters. they do not need to be all that strong ( but obviously must be stronger than ordinary polystyrene).
would anyone know the name of such a building material or any other building material that might suit better please? But being able to slice it into strips with a knife, would obviously be a big bonus for ease of application. thanks