while((tempDegree > 27) && (servoBracket < ventHatch_open)){
servoBracket = servoBracket + 1;
myservo.write(servoBracket);
delay(50);
}
It is pointless to check the temperature in the while statement, since it never changes.
Separate the process of opening the window from the need to open the window. Create a function, openWindow() to actually open the window. Create another one to actually close the window. Do NOT put anything in those functions that is not DIRECTLY concerned with the process (NOT the need for) of opening or closing the window. Those functions will use for loops, not while loops, to open and close the window.
Then, you'll see that a while statement is inappropriate in loop().
You probably want to open the window when one temperature is reached, and close it at a different temperature. Opening and closing the window as the temperature fluctuates around 27 isn't a good idea. Opening at 27 and closing at 25 is.