Oh! so if it's too cold, you close the window but putting the glass on? If so what temperature do you put the glass on?
We have regular posters here keeping chickens in unheated, well ventilated coops at -30 and -40F. What is cold to us humans doesn't ruffle a feather for your little dinosaurs.
In your climate, the only time you want glass in the windows is when the wind would otherwise be blowing the rain inside.