"Christian McArdle" wrote in message
. net...
1. Would be be better to remove any felt with a Stanley knife, install
Tyvek under the rafters in the loft and seal off the eves vents.

or

2. Leave the felt, install Tyvek under the rafers and right down
sealing
the eves vents.

Or even naughtier, rip out the felt, fully fill the depth of rafters with
kingspan, with an additional 25mm below. Vapour check plasterboard and
replace the felt with breathable membrane when reroofing. The two layers
of
kingspan (with joins very much not coincident) would act as sarking...

You would need to tape the Kingspsan to prevent any water entering the loft.