Our kitchen electric oven has a large glass door approx 530 x 440mm, overall thickness 35mm.

There is a front and back glass pane, no insulation and the air cavity is open at the bottom.

I'm wondering if it would be cost effective to insulate the door by filling the cavity with a suitable high temperature insulating material?

Electricity will soon be nearly 0.50gbp per kWh round here, hence my thoughts.

On the other hand, perhaps the warm dry air in the door cavity is already a reasonable insulator? Certainly you can touch the front of the glass without danger of being burnt.


2 Answers 2


If the air cavity is so thin as to prevent convection, it will be almost as good an insulator as a vacuum.

For this reason the air cavity in insulating double-pane glass is normally made so thin as to prevent convection.

It's not perfect, but you'd probably get more effect by gluing reflective foil to the inside surface, to prevent radiation loss.


So My oven door has 3 glass layers, the outer one is cool to the touch - designed for safety.

If you fill the space then you won't be able to see how things are cooking - a downside in my opinion.

The air gap is designed to control the outer glass temperature based on the max inner oven temperature. If you change the filling to something other than air then it may cause the outer surface to be hotter or cooler than it is now. As for the cost, that will not cause a huge change in electricity demand or the total running cost.

  • $\begingroup$ This does not answer the question asked. $\endgroup$
    – Transistor
    Jun 6, 2022 at 9:05
  • $\begingroup$ I agree about the loss of visibility of the oven contents. This could be mitigated by having a 75mm glass "porthole", similar to the arrangement in Rofco bread ovens. $\endgroup$
    – Albacore
    Jun 6, 2022 at 20:15

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