Aluminum foil

[william]

Hi
I have been reading about many of your oven builds and am planning to start mine soon. I built my first oven about 27 years ago it was a bread oven, an Allen Scott design. after the brick work was finished and before the insulation was put on to cover the brick I applied a layer of heavy duty aluminum foil with the shinny side against the brick, this has the effect of reflecting some of the heat back toward the brick. In my business I have built many kilns that I use to melt and process glass and have used this in some of them it is quite effective. My question is that I haven't come acrossed it on this forum, I will admit I haven't read everything but was wondering if some of the more experienced builders here might have a comment on this. I am planning on doing it for my 36" and was wondering if any of you have also.
Bill

[Tscarborough]

Re: Aluminum foil

I think that oven design has moved beyond the need for excess mass and radiant barriers. It is not that those do not work, but they are ill suited to the requirements of a modern home oven.

[william]

Re: Aluminum foil

Sorry, don't understand "modern home oven"

[Les]

Re: Aluminum foil

Bill,

I would think that the reflective properties would be minimal considering it is also an excellent conductor. Just insulate your oven well and have no worries.

[cleverdick]

Re: Aluminum foil

Bill,

I would think that the reflective properties would be minimal considering it is also an excellent conductor. Just insulate your oven well and have no worries.

And also, I would imagine that the shiny side of the foil would immediately become dulled due to the high heat and any moisture emanating from the brick. Not to mention the smoke that would seep through any cracks.

[NCMan]

Re: Aluminum foil

I agree. The foil would most likely have little to no effect as far as insulating properties.

[william]

Re: Aluminum foil

The foil is not for insulation, it reflects heat that is passing thru the brick not allot, but from my experience is the just makes the heat retention a little more efficient. maybe you have to burn a little less wood.that's all.

[david s]

Re: Aluminum foil

If the foil is in contact with any conductive material like dense refractory (firebrick or castable) then it will be ineffective as an insulator. As a moisture barrier however it will be quite effective. This can prove to be a problem later as moisture will be prevented from passing through this barrier. One method that can be used is to perforate the foil with lots of holes to allow the passage of the steam.

[NCMan]

Re: Aluminum foil

I get what you are saying. But, it's really all the same. Whether you call it insulation or "heat reflection", it's all the same, really. You are attempting to slow down heat loss, and I am of the opinion it does not make much difference, if any at all. You may want to think of some actual insulation, if you are indeed serious about heat retention. Also, there is ample science out there to validate what a couple of us are trying to tell you.

[william]

Re: Aluminum foil

I have seen plenty of insulation that is foil faced used in heat applications, as for a steam barrier I never had any issues with my first oven. I baked in it for 22years before I lost it in a divorce. It's is just a concept. I respect your your opinions though.
Bill

[david s]

Re: Aluminum foil

To explain what I meant about foil being a moisture barrier and it becoming being problematic later, my own experience with using it has led me to eliminate it from future builds altogether. I placed a layer of foil between my 10:1 vermicrete insulation layer and the outer cement rendered shell primarily to act as a moisture barrier to stop the vermicrete sucking moisture out of the render layer and compromising its strength. Being aware that the foil would also act as a barrier to moisture passage in the reverse direction I perforated the foil heavily in two places about 10 square inches in each place (one at the top of the dome and the other around two thirds up on one side. Sure enough, if my oven has become a bit wet in the insulation layer (I also have a vent which communicates with the insulation layer to the atmosphere) those two places on the outside of the cement shell become quite hot, while the rest of the outer shell is only just warm to the touch, indicating that steam is passing through the perforated holes at those points.

[william]

Re: Aluminum foil

Hi David
Was this just when you were doing your drying after you finished your build or was this ongoing. I understand that drying out, ,lets say the above cement and vermiculite and the below brick would raise issues all that moisture still would have to be driven thru your water proof coating , if that's how you finished the outside. In my case that was how I finished my second oven with stucco and never could recall any problems. I always assumed that moisture at higher temps would evaporate
Bill

[NCMan]

Re: Aluminum foil

I have seen plenty of insulation that is foil faced used in heat applications, as for a steam barrier I never had any issues with my first oven. I baked in it for 22years before I lost it in a divorce. It's is just a concept. I respect your your opinions though.
Bill

Bill.....you asked for opinions with your first post. You got a few. As for foil faced insulation, it would only have a minimal effect and only then it would need an air gap to be effective at all. Otherwise, it just conducts and therefore transfers heat and has a minimal effect.

[Gulf]

Re: Aluminum foil

I have seen plenty of insulation that is foil faced used in heat applications, as for a steam barrier I never had any issues with my first oven. I baked in it for 22years before I lost it in a divorce. It's is just a concept. I respect your your opinions though.
Bill

William,
Sorry to hear about the divorce, I could never actually afford one myself . If you could sneak back into to the old place and dislodge a brick or two , I bet that that the foil does not actually exist as you remember it. If it was made from aluminum, it will not fair very well in a high ph enviroment .

[david s]

Re: Aluminum foil

Hi David
Was this just when you were doing your drying after you finished your build or was this ongoing. I understand that drying out, ,lets say the above cement and vermiculite and the below brick would raise issues all that moisture still would have to be driven thru your water proof coating , if that's how you finished the outside. In my case that was how I finished my second oven with stucco and never could recall any problems. I always assumed that moisture at higher temps would evaporate
Bill

Bill,

I live in the tropics and my oven is out in the weather, consequently during the wet season the oven gets wet. Mild to medium rain is not a problem, but heavy rain is and the oven needs drying if you want to use it during this time. It's usually so hot that we don't tend to think about lighting fires and scurry into the air-conditioning as a preferable alternative. The oven is restored to normal operation after a few long slow fires, so to answer your question, yes, this is an ongoing problem and the water elimination would definitely be slowed up by the presence of the foil, which is why I don't use it in the build any more.
If you live in a different climate or you have a roof over the oven the decision might be different.

Gulf,
Regarding the foil deterioration, I used foil backed fibreglass ceiling bats in between IFB props as insulation under the floor on my first oven. When I dismantled it, two or three years later, I fully expected the foil to have deteriorated as it was hard up against the dense firebrick floor bricks. There was no noticeable deterioration of the foil apart from it being covered with some wood ash which itself is quite alkaline, I was surprised. The story could be different if it had been there for ten years though.