Has anybody done or know about Plenum for heating cooling through basement? it seems a bit risky if it does not work out. By the way thanks for the info on perolite .

If you mean using the space as the plenum, yes we have done that with a crawl space, using the area as an open return, it works just fine, but down side is you won't be able to pass an energystar test as it will show too much duct leakage