Foam Spraying?

My house is a 1920's steel framed bungalow with a high roof with asbestos tiles. The tiles are all in place and intact; the felt, though, is a crumbling mess which has been tacked up from inside the loft. The tiles are no longer available. The roof is extremely draughty. The roof space is a filthy mess.
I can't stretch to re-roofing. What do you think about spray foaming? Would it be a sensible option, given the likelihood of future problems and a wish to improve insulation in a very cold house? I'm keen to do something about it, but I don't know enough to decide what, so any views welcome.

Kevin

Think twice. There have been reports of foaming lifting slates and it can also cause problwms with ventilation.

and because it glues all the cracked and broken tiles together, it becomes impractical to repair the roof. Stripping it for a reroof will cost a lot extra because of the extra work in prising it off. The timbers will probably rot as they will become sodden and not dry out.

it is a generally hateful idea,

Do a search on "spray foam" in the Roofs forum.
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