# Do you lose much heat when you open the oven door?

How much heat is lost when you open the oven door and take a look inside? Say the heat inside is 475 F, and the room temperature is 70 F. How long does the door have to be open for signifigant heat loss? By signifigant I mean alter the cooking time of whatever is inside?

Got into a slight argument with my dad today about this. He says even 10 seconds will cause a big drop in temperature and will “disrupt the cooking cycle.” Whatever that is. Anyhow I argued that heat dissapates at a proportionate rate to the different temperature gradients. Hotter to cooler will dissapate quicker depending on air movement. I don’t know the math to figure the exact temperature or anything, as I suppose the mass and temperature of the food itself will be a signifigant variable in the equation. I figure opening the door for a few seconds to peek inside will only drop the air temperature inside by a degree or two, and will not effect the food temperature in any measurable way. (unless you have some high tech equipment)

What is the straight dope?

Here’s a start:
The specific heat capacity of air is about 1.0 kJ/kg°C = 0.239 kiloclories/kg°C.
The average molecular weight of air is 29.
At STP, a kg of air will take up 772.4 liters.
What’s the volume of an oven?

It looks like the amount of heat lost through air exchange will be a very small number.

Definately more than a degree or two. Most likely 20-30 degrees but depending on your oven it won’t take very long to heat back up.

Nearly all of the heat capacity of the oven comes from the walls of the oven and not the air. If you only heat the oven until the air reaches the desired temp, then opening the door can reduce the temperature significantly. As much as 20 or 30 degrees in my oven as measured by an independant oven thermometer. However, if you allow it to preheat so the walls come into equilibrium, then theres much less of a drop.

I also keep a thick, ceramic pizza stone on the bottom of my oven as well to add yet more thermal mass.

I think this is a case that cries out for some empirical research on the part of the OP. Heat up your oven. Once the light goes out, open the door for a measured period of time. The light should come back on as heat is lost. Close the door, and move the dial down until the light goes out to see what temperature the oven is now at.