The ridge tiles on the roof would be 10cm higher than usual. In the gap would be the top half of the blades, shaped something like a drill bit.
Assuming a 10m long roof, this would give you an area of 1m2.
I assume that the wind will be stronger at the ridge than the surroundings as the roof deflects it upwards.
Some non-trivial modifications would be necessary to the top of the triangular wooden support thingies to make a single turbine, so probably easier to have a smaller turbine between each TWST.-- marklar, Dec 16 2010 diverted wind flat turbine generator Discussed at length by HBers mostly claiming its not worth the try [pashute, Nov 06 2012] Roof Ridge Windmill http://cleantechnic...ating-wind-turbine/Same idea from 2009 [marklar, Aug 28 2013] What's a TWST? Oh! "Triangular Wooden Support Thingy"-- pashute, Nov 06 2012 Birds and squirrels could nest there, on calm days.-- popbottle, Aug 28 2013 random, halfbakery