Reflective covering under dome insulation

[nrobert]

Has anyone used a reflective covering such as aluminium foil over the dome underneath the insulating layer to reflect heat back to the oven?

The idea comes from seeing a lot of thermal insulation for buildings with a silver reflective coating on them. Presumably this is to reflect heat?

Any thoughts?

[Ken524]

Re: Reflective covering under dome insulation

Aluminum foil over the dome is a waste of time (and aluminum). It reacts with the refractory products you use to build the dome and disintegrates. Save your foil for wrapping up the leftover pizza!

Here's a post by Dmun about this subject from a different thread:

The aluminum foil idea has been debunked again and again. There's no use for it in oven building except to create a non-adhesion layer between different masonry parts, for a slip plane. Since it decays in the presence of the corrosive mortar, it doesn't have any heat reflective properties.

[david s]

Re: Reflective covering under dome insulation

Because the foil is in contact with the dense inner dome it will conduct heat through it. For a foil layer to work it would need to be surrounded with air. I tried a foil layer between my vermicrete layer and under the outer stucco/rendered outer shell in an effort retain moisture in the outer shell when it cured. I wish I hadn't because it tends to lock moisture in the oven making removal of moisture more difficult. Fortunately I made lots of pin pricks through the foil layer in two patches about 3" in diam. Now after long periods of tropical rain when refiring the oven these patches get quite hot on the outside while the rest of the oven is only warm on the outside. This indicates to me that water/steam is passing through those holes and super heating the outer shell at those points. It is also a gret indicator that my oven is dry when those spots are no longer hot, but the same as the rest of the outer shell. It is not too much of a drama, a few long slow fires gets the oven back to normal working condition, but it does take longer than if I hadn't used the foil. It also indicates to me that the foil has not disintegrated. Perhaps being outside the insulating layer where it is a bit cooler has prevented it from corroding.

[nrobert]

Re: Reflective covering under dome insulation

Thanks for the feedback, makes sense, saved me from making a mistake, great forum.