I'm well aware that rooftop turbines are not a good idea domestically, we've got some windswept fields facing to the prevailing wind so was thinking of a 15Kw installation. First stage is to erect a tower and measure the wind for a year.
There's a lot to consider beyond feasibility; - planning permission, lifespan and reliability of equipment and 'will the government stick to the deal'
Some years back I did the calculations on insulation using the U values and all that. There is a law of diminishing returns. the recommended depth of loft insulation has grown from 4" to 6" to 12" as the price of energy has risen. Assuming it is, as threatened, going to jump again, it seems reasonable to assume greater depth will become recommended shortly after.
As for the condensation, not heard this. Assuming the roof isn't leaking and the ventilation into the loft is as required, I don't see it being a problem. I'd look around on some building forums or seek advice from energy saving trust if it's a concern. We do have some good builders on this forum if they care to comment, it would be appreciated.