It’s generic foam pipe insulation, approximately 3/4" thick.Originally there was also a 3-4 meter section of pipework from the collector output to inside the roof that was completely uninsulated, I’ve gotten that sorted.

I bought the place a couple of years ago and after replacing the seized circulating pump early last year I was pretty disappointed with the system’s performance.

At that point I put onewire sensors on the tank and lines on the ground level and measured it for a few months and didn’t see much heating at all from the collector.

I couldn’t get to the collectors for a long time, not having a three storey ladder, but I got suspicious after sunny + windy days resulted in very little heating. Finally got up there about three months ago to discover that bare section of pipe and insulated that.

Collector temperature I haven’t measured using the original analog sensor yet, I just let the original controller do its thing to get a baseline. But currently in a “warm” Australian spring the maximum outlet temperature at ground level is a brief peak of about 65 degrees C at around 1pm. Going off the circulation rate of the pump it’s probably 40 litres of water at that temp before it starts dropping back down in the afternoon.

Insulating that bare section of pipe improved performance but it’s still not fantastic, so now it’s time to drive the pump with my own algorithm and see if I can improve things.