www.buildinggreen.com/feature/foll... it's an old article, but the physics haven't changed. I would also add that at today's price points, solar makes exponentially more sense than small scale wind energy, even when installed on an appropriate tower and performing optimally.

I recall an article in home power magazine decades back, and I spent 15 years in residential wind power before moving to solar. Will see if I can find the article. Rule of thumb is to put the bottom of the blades 30 ft above any surrounding obstructions within 300 ft.

More on energy content. the available energy in the wind is proportional to the velocity cubed, so slight increases in velocity yield massive increases in energy, and the cheapest way to gain velocity and avoid turbulence is a tall tower.

Thanks for asking. Turbulence and vibration are the first two reasons. There's a huge vertical component to the wind at the roof's edge that will ruin energy content. Turbine RPMs can also hit the resonate frequency of the structure they're mounted to and ring the building like an acoustic guitar.