I looked at many ways to build an enclosure for my temp sensor and finally came up with this idea. I have used thermo-siphoning in the past to heat a boiler full of water from a wood stove, so I knew that the technique worked. Here's what I did...
I got 2' of 4" abs from Home Depot and mounted the sensor holder inside it using 1-1/2" threaded nylon standoffs from McMaster-Carr. That puts the sensor right in the middle of the tube at the bottom. This is looking at it from the bottom end.
I couldn't find any little chunks of 6" thin wall pvc so I had to buy a whole length and cut off a foot. I put 6 stainless set screws around the top and bottom to act as standoffs. The pvc would provide shade for the bottom of the abs.
I found a little smoke stack hat at Coast To Coast to keep the rain out. I used 3" bolts and some conduit hangers for mounting, to hold the whole thing to the pole. I got those at HD
So here it is mounted with the sensor in it. The idea is that as the sun heats the upper part (ABS) it causes the warm air to rise, which draws cool air in from the bottom and exhausts it at the top.
I can always add a little more ABS if there's not enough suck power. Or if it just refuses to work I can put a solar powered fan in the top.
Even if it doesn't work it was fun trying it.
http://www.datilcam.com/