It's one of our favorite days of the year, Pi day, a celebration of all things round. Last year we partied over a delicious mushroom pi. And why is it green? As Bucky Fuller would remind you, a circle encloses the maximum area per unit of perimeter, a sphere the maximum volume. It is theoretically the most efficient form.
This year we round up all things round, our celebrations of Pi Days past.
Three years ago we celebrated all things round, including Rolf Disch's solar powered house that tracks the sun, so that its triple-glazed front can face the warming sun in winter and show its well insulated back in summer. Then there is the wonderful water tower conversion by zecc arcitechten of Utrecht. A pie shaped kitchen would be an interesting place to work, and then there is Eli Attia's way too big Round House.
Rotating houses tend to be round, and are worth looking at again on Pi Day. See Rotating Houses Put A Whole New Spin on Green Design
Warren used Pi Day as an excuse to include pictures of round things in his post on Britain's Burgeoning Bicycling Boom
In case mushroom pi doesn't strike your fancy, here are recipes for Apple Pi and pumpkin pi.