system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How much heat does a pre-heated oven lose when you open it up to put in the food?

If I pre-heat my oven to 400 degrees, then I open it and leave it open for 10-20 seconds or so to carefully put the food in the middle of the center rack without burning myself, I can feel a mass of hot air venting out of the oven, but the electronic thermometer doesn't change. Am I actually losing a meaningful amount of heat?

If so, do the recipes that call for a very precise bake time ("32 to 34 minutes") compensate for this reality that for the first few minutes of the bake time, the oven is not at the optimal temperature?
gpt
One factor not mentioned is that the sides, top, & bottom of the oven chamber, along with the rack or baking sheet you place the food atop, being solid metal will hardly give up much heat the time the door is opened to place something inside the oven.

This is the purpose of preheating, for it takes longer to heat up the metal than the small mass of air inside the oven chamber.

Which after the food is placed inside & the door is again closed, it will take little time to heat the air up again to proper temp.