First day - Should I leave this window open?

[LedbetterHomestead]

Got these today, Is it okay to leave this big door open or should I close it? The weather is overcast around 76 degrees.

 

[rosemarythyme]

I would have it open as long as you don't have strong winds coming directly into the brooder. I brood in a temperature range of mid 40s to mid 60sF in this set up (back side is the same), and it stays open 24/7 (though I slant pieces of plastic over it in rain).