Have no idea....

[Wayne B. Wilson]

http://www.volko.com/turbine.htm
As Larry posted

[hlowe]

They are used a lot in Canada.

[Brian A. MacNeish]

Originally Posted by hlowe

They are used a lot in Canada.

I’ve never seen one of these on a chimney.

The large Canadian HRV company, Venmar (now owned by Broan), grew from these in the early 1980's but.........now do not make them. (see http://www.venmar.ca/ve_basse_multi_eng.aspx ) They do not make them because they don’t work well and can allow downdrafting. Until they stopped making them about 1990-2, I believe, I fought against this concept and company until they moved to making air exchangers and HRV’s. I now consider them as producing one of the best 2 HRV’s!!!

On Sunday past, I was working in the World Heritage Site and historic fishing community of Lunenburg, NS (http://en.wikipedia.org/wiki/Lunenburg,_Nova_Scotia ) and drove by a house with two turbines on the roof.......both were covered and sealed with plastic bags and duct tape!!

These turbines are in my "Smoke and Mirrors" list of popular energy misconceptions. In the mid-late 1980's, Canada Housing and Mortgage Corp. sponsored testing by an engineering firm to determine the effectiveness of increasing ventilation versus other methods. Turned out that they were slightly better (8% or so) than the "chicken coup ventilator"consisting of a vertical pipe/duct with a conical rain cap (think of the Tin Man).

The main mover of air in both of these units is (1) wind moving over the top, creating a draw like wind over the top of a chimney flue and (2) if there is warm air in the attic from air exfiltration through ceilings, etc or from solar heating of the attic, the chimney or stack effect is working (warm air rises).

The turning turbine creates the mind illusion of a fan which we know moves air....... but the fan is driven by high grade electricity converted to mechanical energy. The wind driving force for the turbine is not converted to another energy type nor is it stepped up or down in quality nor is its ability to do work multiplied as it is in our simple tools such as a lever, screw or pulley. Thus the turbine ventilator "appears" to create "work" and is "Smoke and Mirrors" or an illusion.