John, I have noticed some of the instrument shelters contain a small fan to help with air flow. As I'm still constructing mine I would like to get your thought on the use of fans in the shelter, thank you.
Having proper ventilation for temperature and humidity measurement is very important. You can either do it with the design of the shelter or by adding a fan. So I guess it would depend on the design of your shelter as to if you should ad a fan. Adding a fan to any shelter is fine and will not hurt measurements taken with a shelter with good ventilation.