I have a double sided fireplace. One side is open and the other is glass doors. The glass doors are closed but air still gets through and it contributes to my fireplace spilling smoke into the room. We are going to replace the glass doors with what amounts to a glass window so that side is completely sealed. Am I ok to go with tempered glass or should I go with pyrex or something else? I used my thermapen to measure the temp of the glass doors tonight with the fire going and it was about 275. I know that's within the acceptable range for tempered glass but I didn't know if I should go with something more heat resistant to be safe.