Bear in mind that some lofts do experience condensation. Even some of those with breathable felt.
That should be enough insulation, and if the felt is held open at the laps - every lap between every rafter and the air moves some tissue paper held up in front of the openings then that should normally be enough as it is the equivalent of a ventilated eaves. Yes cover the header tank.
If that still is not enough, and this condensation is a regular occurrence not a random one-off, then the next option is to fit a series of tile vents to each side of the roof.
That should be enough insulation, and if the felt is held open at the laps - every lap between every rafter and the air moves some tissue paper held up in front of the openings then that should normally be enough as it is the equivalent of a ventilated eaves. Yes cover the header tank.
If that still is not enough, and this condensation is a regular occurrence not a random one-off, then the next option is to fit a series of tile vents to each side of the roof.
