[Greenbuilding] Barra system

[Paul Newby]

> Barra's system seems to have some distinct improvements to be noted. 
> However, my preference would still be to choose a vacuum solar tube 
> system as a collector since the heat-carrying agent is a liquid, and one 
> can use a liquid which will not freeze if there's a chance of that 
> happening.

My point of reference for this is a solar-assisted hydronic
radiant floor system using liquid for heat storage and
transfer.  But such a system is still fairly expensive,
and it seems, admittedly based on a very limited sample,
that solar panels producing hot air are significantly lower
in cost than panels storing energy in liquids, but lacking
storage, they have limited application.  So a counterpoint
might be a Barra-type system with some other means of providing
heat (e.g., woodstove) when solar gain is limited.  Seems
to me this could potentially be significantly lower in
overall cost...

Paul N.