I work for a UK manufacturer of a 5kW turbine.
Building mounted turbines are more for your “green washing” activity, Vertical Axis turbines are, in my opinion, not worth the outlay for the return they give.
The most important factor when considering a wind turbine which will enable you to claim the FiT (Feed in Tariff) is MCS accreditation, no MCS no FiT, fact. If anyone tells you their turbine is “just about to be approved” then they and the figures they are putting forward are not worth the air they are written on.
MCS: http://www.microgenerationcertification.org/mcs-consumer/product-search.php?searchProductTypeID=4551
That site is also your first point of call for any solar etc.