The location I have only gets sunlight from the southwest and due west, i.e. only afternoon / evening sun. So I got an old biscuit tin and cut two sides off it. I rolled over the cut edges to avoid injury, and painted it white with several coats of gloss paint, hoping this will both reflect and weatherproof the tin. I then mounted it in the appropriate place:

It works well. It doesn't get any direct sunlight, and I don't think it will even in the height of summer. The perspective on the above is shortened; in actual fact, there's loads of space for air circulation. And I no longer get false temperature spikes with the sun low in the sky

