9 Sept: Chris Wood's work with Bullivants was highly recommended in the Lord Stafford technology innovation prizes in 2010. See the video on the Lord Stafford site. This is about solar charging of foundations. Chris's work is based on the build up of heat in roof tiles. See the Lord Stafford page and movie You have to click on the Sustainability award, and the coverage of Chris's work is from 3:50 to 7:00.
I strongly recommend Chris to include Sunboxes in his next project, although of course these require some smart architectural incorporation (being on the wall), whereas the roof tiles are visually 'invisible'. For the rooftiles, it seems to me that the plumbing must be a bit complicated, with many small pipes and joints! But chris assures me it is done with very long loops of small bored plastic piping similar to that used in under floor heating.
Actually, you should also checkout the preceding minutes of the same video, as the housing scheme shown is also using solar heat in the foundations, but forming insulated boxes below the slab. We are all moving in the right direction!