looking for info on how to install earth tubes my building is 24-40 would like a closed loop

There is threads here on them. But I installed two 6" 100' for fresh air, or exhaust. Use smooth, glued together tubes with nowhere for water to collect.

Why closed loop? I don't know that it would be worth it.

There is a decent article in the current home power mag about a system which includes an earth tube. Not exactly a how to article, but certainly worth the read.

I read that article and they showed a picture of it. It was a long deep trench, where did it surface? I think it is important to pitch away from the building and to "daylight". You don't want it to hold any water, if it does it could be a lot of trouble.

The Home Power one was deep, 10' and they got good results. For mine I couldn't be deeper than 4' and get to daylight.

I have seen several that basically just looped the home, in the main excavation. An aquaintence has a closed loop in his home, in Boulder Co,and it supplies all his cooling, No AC. (Net Zero home)

There are some systems that have anti Microbial filters. Always slope tubes to prevent moisture from collecting.

Where does condensation in the tube go?

A trap with a small hole into sand (or the house sewer drain) might be enough to get rid of condensation. Or numerous small holes along the tube.