What do we line roof with when there's no roofing felt?

We have a 1930s house where the roof is just tiles straight onto the rafters ie no felt. We really need to put something up under the actual roof, mainly to stop the dust/etc getting in. My huband is keen to put up that foil/bubble roll stuff by putting it over the rafters. I'm concerned that this will mean that any moisture that gets in will have no where to go and potentially cause damage to the wood. Anyone with any suggestions/advice please?

Paper.. your right about the bubble wrap (or insulation board etc) will cause any water that gets past the tiles (when they slip) to gather on the rafters and slowly rot them.. also youll get ALOT of condensation internally.. Use builders paper or similar breathable membrane to line the inside over the rafters.. that way when theres a leak youll see the paper disintergrate and its easy to access repair and replace the paper

I am having exactly the same problem. What is builders paper? The only paper on a roll that I have come across is the brown wrapping paper for parcels. That tends to be a bit thin. Is there anything thicker and more robust?
What if you used the alub-bublle stuff between the rafters, so that it only covers the underside of the tiles, and most of the rafters are left exposed. If you have air bricks in the walls, wont that let enough air in to ventilate the rafters?

builders paper..............The Sun .......go for the breathable membrane, as suggested..............commonly used now by roofers, and available from roofing merchants