2024 Neapolitan oven build

[daidensacha]

Stainless steel door insulation… Rockwool or Cermaic fibre mat??

After a sequence of obstacles slowing/ delaying progress of the oven, this week things opened up. I picked up the stainless steel parts for the flue, and tomorrow all going well I‘ll be putting the flue up through the roof. Excited for that, because then I can start with a week of drying fires.

Last week I picked up 2 stere of Ash firewood for the oven. Nicely dried, and stacked under the terrace roof.

This week I was 2 days in an engineering factory, putting together 2 doors. One stainless steel that I can fill with insulation, so I can retain heat and use the oven over daysn following cooking pizza. The second door is a steel one, without insulation. I didn‘t expect it to be more heavy than the stainless steel one, but it is. Rustic, but heavy.

When I was at the factory picking up the roof profile for the flue, the boss was really friendly and gave me about 1 metre of the roll of Rockwool, to fill the stainless steel door. It was really generous. I ordered ceramic fibre blanket about a week ago for to fill the door, and I have consulted google but could use input as to which would be better. In terms of temp, the Rockwool would still be ok, as I don‘t see the door getting to the 1000C melting temp of the Rockwool.

What I know from handling the two products, is the ceramic fibre compressed but doesn‘t really spring back, whereas the rockwool is quite fluffy and I could imagine that if I fill the door with it, it will spring out and fill the entire inside of the door. The ceramic fibre blanket however, if compressed will not spring out and fill the door. I couldn‘t find info on Google comparing the two products insulation efficiency, to know which would be better. I‘m sure however that some of you out there have experience with it.

I‘m really happy with the door itself, so far without testing it. It fits perfectly, with allowance for expansion. I made it so I can remove the back to check, change or renew the filling. I still need to drill and tap some holes around the sides to fix the front and back with countersunk screws.

[daidensacha]

It is hard to tell from your drawing but it is recommended to have your chimney extend 3' or roughly 1M above the highest roof point with in 10' or 3M. You may have that but it is hard to tell from the drawing. I know that I had to add another section of chimney to get up high enough.

Randy

Hey Randy, thanks for your input.

Here in Germany, by law any flue going through a roof has to be cleaned by a licensed chimney sweeper. He knows the laws, and came around to inspect the oven and fill me in on what was needed by law.

• Yes it does go 1 meter above the roof, which is ok here.
• It’s double walled flue, so needs 7.5 cm clearance from flammable material with air space in between the flue and the roof where it goes through. Or, it needs to have 20 cm clearance between the flue and flammable material. I‘m having 7.5cm with space for airflow.
• There cannot be a living space above the flue. We have an attic, but its not a living space.
• Has to be 15 meters clearance to neighbours windows.

All the boxes are checked. The chimney sweep will visit again once I have had my first fire to check it off.

I pick up the flue Monday and have a little planning to customise the flashing to fit on the roof profile. Keen to have it in so I can start with fires.

[nlinva]

I think the general rule in the US is 3 feet where it penetrates the roof, and 2' above anything within 10' horizontally. While the drawing does not give precise measurements, it does give the general impression of meeting that standard, I believe.

[RandyJ]

It is hard to tell from your drawing but it is recommended to have your chimney extend 3' or roughly 1M above the highest roof point with in 10' or 3M. You may have that but it is hard to tell from the drawing. I know that I had to add another section of chimney to get up high enough.

Randy

[daidensacha]

Terrace Roof on, Stainless steel flue on chimney next

The terrace roof Sandwich panels and flashing were delivered on Tuesday night. Put the panels up on Wednesday, and been finishing of the flashings. This afternoon I completed the slide flashings.

Having the roof on has allowed me to remove the tarp which I‘m really happy about. It was sweating with the tarp on at nights, and water condensing at the top of the chimney. It’s slowly been drying since I removed the tarp, albeit slowly as its getting colder. Max 10C today, and next week getting colder from Wednesday.

I have ordered the flue and it is being manufactured this week. Looking forward to installing it on the chimney and through the roof so I can get some drying fires started. The base plate will insert into the existing Ø200 mm Schamotte flue, with a base plate that will mount on the top of the brick chimney. In total, from the beginning of the vent to the top of the flu will be 2.9 meters.

[daidensacha]

I'm also at the making-a-door stage, so have been thinking about some of these same issues.

My guess would be that most heat reaching the outside of the door will get there through the conduction of the steel sides, so the specific type of insulation inside would not matter as much.

One possible advantage I have considered of the CalSil is that, being rigid, it will help the door keep its shape, against possible warping tendencies under high heat (though it sounds like you'll be using thick enough steel that that would not matter).

Also, since we want there to be some space on the sides and top to prevent the door from getting stuck upon expansion/shrinking, there will always be a route for heat that bypasses most of the thickness of the insulation (basically a short diagonal from the inside of the oven through the inside corner of the door to the air channel on the side). How much this will matter I'm not sure, but it makes me wonder about whether thicker insulation really matters a lot (i.e. does 4" make a big difference compared to 2"?).

I was just working on a spreadsheet to compare the price and weight of stainless steel vs aluminium.

For my door material, pieces ordered cut to size.

Material	Weight (kg)	Price (Euro)
Stainless steel	8.02	153.56
Aluminium	4.15	84.19
Ceramic Fibre	1.8	20.00

Stainless steel door would be 9.82 kg, vs Aluminium 5.95 kg. Nearly 4 kg difference.

With the Alu, the price is for 2.5 mm sides, top and inside, with 4 mm outside. Even with ceramic fibre I think it will be solid enough, as long as it‘s not being thrown around.

I‘m sure I can save a little on price by shopping around, but its a big saving to go with Aluminium.

I allowed for 5 mm gap on the sides and on top of the door to allow for expansion. Aluminium is a better conductor than stainless steel, and will heat up faster. Having thicker insulation by my reasoning has two advantages. 1. Less heat lost through the insulation from inside to outside the door. and 2. The sides being longer mean its further for heat to move through conduction.

The bricks on the sides of the door are thermal mass, so being heated, any heat on the sides of the doors will not be lost to the bricks as long as they are hot.

[nlinva]

I'm also at the making-a-door stage, so have been thinking about some of these same issues.

My guess would be that most heat reaching the outside of the door will get there through the conduction of the steel sides, so the specific type of insulation inside would not matter as much.

One possible advantage I have considered of the CalSil is that, being rigid, it will help the door keep its shape, against possible warping tendencies under high heat (though it sounds like you'll be using thick enough steel that that would not matter).

Also, since we want there to be some space on the sides and top to prevent the door from getting stuck upon expansion/shrinking, there will always be a route for heat that bypasses most of the thickness of the insulation (basically a short diagonal from the inside of the oven through the inside corner of the door to the air channel on the side). How much this will matter I'm not sure, but it makes me wonder about whether thicker insulation really matters a lot (i.e. does 4" make a big difference compared to 2"?).

[daidensacha]

Door Design and considerations

rsandler Thanks for your input.

I’m questioning whether I will add the thermometer or not now. Add it in the door means cutting holes for it, that at a later stage I might regret. When I‘m n it clear on something, my ideas start as seeds and evolve as I become clearer and more informed. I‘m not attached to adding the thermometer, and remaining flexible as to if, or where I might add it if I choose to proceed with that.

I‘m still researching and informing myself with my door design.

I would like to use stainless steel to make the shell. I have a piece of 10 cm thick calcium silicate insulation left over from what I used under my floor.

Stainless steel shell
Trying to use minimal thicknesses so the door stands up to its life, I thought 1.5 - 2mm thick on the sides, back and bottom (2.92kg), with 3mm thick front (2.82kg). Estimated total 5.74 kg only for the stainless shell.

Calcium Silicate fill
The Calcium silicate weighs in at around 5 kg, and then I would have handles to consider. That would make my door around 11-12 kg in total, solid but hefty.

Ceramic Fibre fill
As an alternative fill, I could also use Ceramic fibre blanket, much lighter at approx 1.8 kg to fill the shell. The door in total would come in then around 8 kg, and 3-4 kg lighter than if I were to use the Calcium silicate.

The Ceramic Fibre blanket is 128KG/m³, with rated max temp of 1260C (vs Calcium silicate 1000C). Theoretically Ceramic fibre is lighter, and withstands higher temps.

I‘m all for lighter given I will be sliding the door in and out more than others. What would be good to know before deciding, if someone knows, is the performance difference between the two types of insulation. Using 10 cm fill in the door, how likely is it that the outside of the door will get hot? I know the heat will conduct along the sides, but here I‘m more interested in what heat will get though that insulation.

[rsandler]

FWIW, in my first oven I had a probe through the door (it was a long-stemmed deep frying thermometer stuck through a small hole, nothing fancy); it is just as well that it was removable because the probe did fail after several years. On oven #2 I left off the thermometer to start with, thinking I could always add one later, and haven't missed it particularly. Certainly haven't felt compelled to make a hole for a new thermometer. Your mileage may vary--I do have the experience of having a wood fired oven for 10+ years, though my oven #2 performs very differently from oven #1. But if you make your door reasonably moveable, I find it's always easy enough to just open up and shoot it with the IR thermometer.

[daidensacha]

david s My first job many years ago was working in a pizza bar in Kalamunda, Perth. 2 years, albeit with an electric oven, there is no substitute for experience. Indeed, reading the oven became second nature, and for that reason I wasn‘t to interested in placing a thermometer in the dome, or inside the oven.

I thought the door, if it was practical would be the way to go, but only to get a read on the oven chamber temp each day following the fire to gauge what to cook if I want to use it to cook bread, meat, or cake, or other stuff.

I did a simple test with this thermometer putting it in boiling water. Next step was testing in in/on my gas BBQ. My BBQ is a beauty, can get it up to 300C, so I wanted to test the efficiency of the thermometer I have against the stainless steel top when its hot, as oppose to being exposed inside the BBQ chamber.

Could be worth getting a different type of Thermometer as you describe with a sheath going through the door. Then I can remove the thermometer to replace if it’s ever needed.

I can also just revert to using my infa-red thermometer gun, and get to know my oven. Might just be the best in the end.

[david s]

[QUOTE

A couple of notes on insulation thickness:
- it's actually not true that 'there's no such thing as too much insulation':

[/QUOTE]

While the chart illustrates the reducing effectiveness of increased insulation because the graph is not a straight line, the issue is compounded by the massive increase of area required for each subsequent layer of blanket, This means that costs go up far higher than the reducing amount of gain via heat loss.


Mountng it in the door leaves it more vulnerable to damage.I think a sheath is advisable for all probes. Nearly all temperature measuring devices, particularly electronic ones, stuff up sooner or later. Most oven owners get to know their oven characteristics, time taken to get to temperature etc. and rely less and less on measuring devices.Here are a few:

1. A fist held in the oven centre and counting how long you can hold it there.
2. A hand held to the outside of the oven
3.The degree to which the carbon has burned away inside the oven
4. The intensity of of the radiant heat felt with an open hand at the entry
5. If cooking pizzas the visuals and time taken to reach that point are all you need.

When the oven consistently does the same thing every time you fire it, you begin to use these methods far more than any other measuring devices.

I'm interested in the chart you posted. Whilst all insulating materials would show similar heat loss vs thickness results, what specific insulating material and its thermal conductivity was that test conducted on?

[daidensacha]

Toiletman Good points about how the thermostat functions. I hadn’t considered that, and now I’m curious. The tube that runs from the thermostat to the probe is can be bent to shape, like its copper at a guess. Quite long, over a meter. But I don’t want to run that into the oven chamber.

I wrote to the vendor I bought it from on Amazon and they wrote back that they have asked the manufacturer for installation information. They will let me know as soon as they get that, and I’ll share it.

The weather here is turning cold, and i’m tackling tasks now one at a time as each depends on the completion of the previous. My roof sheets are due to be delivered on Tuesday, so Wednesday I’ll get those up, and hopefully complete it same day.

Then I need to put a flue extension up through the roof, and seal it, which has its own complication as the Sandwich panels are not flat on top. But hoping to have that completed by weeks end, depending on whether I can source my flue materials this week. Going to a local factory this morning to see if I can get a deal on the parts I need directly from them.

Then I need to do my drying fires, which will take a week or so. Following that, depending on temperature I’ll do my final render. I’ll need luck with a few warmer days for this to happen this year, so keeping my fingers crossed. But it’s looking like I’ll be having pre xmas pizza and glühwein, yay.

Where I live is a small village, and I’m the crazy Australian building a pizza oven that every one here is totally impressed with, but can’t understand why. We will have a village pizza party.

[Toiletman]

Just wanted to add some compliments on your progress and build quality once again: looking great! I'm slightly jealous that you made such progress while I have closed for the season (and was enjoying the beach).

A couple of notes on insulation thickness:
- it's actually not true that 'there's no such thing as too much insulation': for pipes or spheres, by adding insulation you also increase the surface area of the thing that you are insulating: there is a maximum after which adding more insulation actually makes performance worse, as the increase in surface area is more significant than the decrease of heat transfer due to insulation. However, this maximum is far away from realistic sizes for ovens, so you are indeed making the heat loss smaller with your large thickness of insulation (see attached graph, based on my oven dimensions).

Thermometer Installation

I wonder if someone has experience and knows how to install a probe thermometer as in the following image?

What I don’t know, and documentation doesn’t make clear, is how and where the thermometer probe should be placed. Should it protrude through the inside of the door and be exposed, or can it be placed under the inner stainless steel face?

Appreciate any input.

Did you already ask the the manufacturer/seller? Do you know what the working mechanism is?

I have no experience with something that looks like your picture, so below is more generic/speculative info:

Thermocouples/thermistors typically have a very small sensor very close to the tip of the probe, so these could be mounted perpendicularly to the face of the door, with the tip sticking into the oven, or just flush with the SS wall in a little hole. However, these typically come with a display and a power supply instead of a clock.

If the working mechanism depends on expansion of a gas or liquid, or deformation of bimetallic spring or sth like that I would imagine that the full tube has to be immersed in the heat, so then it should be mounted in parallel to the wall. Mounting it behind the SS will result in a small temperature difference vs the actual air temperature in the oven, but as the sensor will be sandwiched between insulation and the stainless steel might not be very large. (assuming you are interested in 10-20C accuracy, not in single digit).
Does the manufacturer specify what the material of the line attached to the probe is and if it's supposed to be exposed to the high temperatures as well? If so you could mount the probe on the 'inside' of the oven, to the back of the door, guiding the wire through the insulation.
It might be that the probe has been designed to be embedded into a firebrick, with the thermal mass surrounding the probe and thereby also giving a more accurate reading of the actual temperature of the mass of the oven, instead of for instance the radiative heat received by the probe or the SS wall of your door. If this is the case you might consider adding a brick with a hole in it on the back of your door, or partially embedded into the insulation. Or you could reconsider the location completely and mount it in the oven instead of in the door.

[daidensacha]

Thermometer Installation

I wonder if someone has experience and knows how to install a probe thermometer as in the following image?



I’m designing a door, which is where I want to install it, simply to monitor the internal temp in the days following heating it to cook pizza.



This is a screenshot of the sketchup plan I’ve been working on. It will be filled with left over calcium silicate insulation that was used under the floor. It will be 100 mm thick, with a 3mm stainless steel front. The sides and back will be 1.5 - 2 mm stainless steel sheet.

What I don’t know, and documentation doesn’t make clear, is how and where the thermometer probe should be placed. Should it protrude through the inside of the door and be exposed, or can it be placed under the inner stainless steel face?

Appreciate any input.

[daidensacha]

Moisture driven out by fire and trapped in the insulation layers (blanket and p/vcrete) has a much better chance of finding its way into the atmosphere if it’s not held back by a hard rendered shell on the outside. Coupled with the assistance of sun and wind to dry the outer surface at the same time, so yes, the drying fires are best done before final render coats.
This then creates a problem of applying the outer render to a dry surface. My remedy for this is to cover the whole oven with clingwrap after completing the outer render so moisture is then retained in that layer for a week. Considerable strength improvement is achieved if it’s damp cured for a week.

I‘m just so impressed by how hard and how quickly the v-p-crete sets. I cover it at night to prevent it getting added moisture from dew, and go out to uncover it first thing so it can dry out throughout the day. This morning I was pleasantly surprised to find the surface of the v-p-crete dry, and by days end it became really hard. When mixing it, it is hard to imaging how solid it becomes. Looking forward to the next stage of drying fires.