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Roof wind turbines for homes: honest guidance
A wind turbine on the roof is the most tempting idea in small wind — no garden needed, the tower comes free with the house. It is also the most common way people waste money on wind. The air just above a roof is the most turbulent, weakest wind on the whole property. That said, there are specific roofs and specific machines where it works.
Why roofs are hard: the turbulence problem
Wind flowing over a building separates at the ridge and recirculates — a churn of eddies that can be 30–50 % weaker than the free stream at the same height, and constantly changing direction. A horizontal-axis turbine must face the wind; in rooftop turbulence it yaws back and forth all day, losing production and wearing its yaw mechanism.
Vibration is the second problem: every blade pass transmits a small pulse into the structure. Over months it travels through the frame as a low hum in bedrooms below. Proper mounts with elastomer isolation reduce it; they do not eliminate it.
When a roof turbine does work
Three conditions, all of them necessary: a tall, exposed building — the roof must be at least 3–5 m above everything around it within 20 m; a vertical-axis or furling machine rated for turbulent, gusty flow; and a load that suits modest, variable power — LED lighting, electronics, ventilation, a small pump — not a whole house.
The best real-world case is a VAWT on a coastal or high-roof building: our Darrieus-H machines take wind from any direction, need no yaw, start in 2.5–3 m/s, and their straight blades mount on a simple frame off the ridge. On a farmhouse gable or a three-storey coastal roof they produce honest, useful energy.
What the roof itself must carry
A small 400 W–1 kW rooftop machine weighs 20–60 kg with thrust loads of a few hundred newtons in a gale — a structural steel bracket bolted through to rafters or a concrete frame handles it. Anything above 1 kW on a roof needs an engineer's letter; the loads are no longer trivial and most roof warranties will be void without one.
Access matters too: every turbine needs inspection twice a year. If the roof needs a scaffold to reach, maintenance costs will quietly eat the energy savings.
The decision rule
If you have open ground and 5 m/s at 10–12 m, buy a tower turbine — more energy per dollar, no structural risk, easier servicing. If you have no ground but a tall exposed roof in steady coastal wind, a properly mounted VAWT is a legitimate choice. If you are in a suburban street with trees around, spend the money on solar panels instead — we would rather tell you that now than sell you a machine that disappoints.
