Most of our customers are weekend oven users so a couple of layers of blanket are more than enough for their insulation needs.
If you plan on using your oven more than the average person, or you live in a state that occasionally gets snow, you should consider wrapping your oven with a 3rd or even 4th layer of ceramic fiber blanket.
Dollar-for-dollar, a second box of blanket is the best investment you can make for your oven.
2 Layers – If you want to fire-up the oven for a fun Weekday or Weekend night. Not planning on making more than 25 – 30 pizzas / bread.
3 Layers – When you plan on doing some heavy duty baking for a couple of days. The 3rd layer of blanket will help retain more heat for the next day. Especially helpful in those cold states (if temps go below 40 at night – that’s a cold state to me).
4 Layers – Starting a backyard bakery? Add a 4th layer and your oven will be Super-Insulated for a full week of baking!
I am heading down the path of more heat retention in my oven (Duratech damper, door, second roll of insulation). As I think about the insulation and doing 4 layers, I am wondering about the girth of the oven in relation to the base. Right now, I have 6.5 inches of space from the oven firebrick to the outer edge of the frame brick. The cermaic blanket appears to be 1.5 inches thick (uncompressed). Quick math: 4 layers of insulation = 6 inches of thickness. Add 1 inch of stucco to get a total of 7 inches added to the oven and I overflow the frame brick.
Should I compress the insulation before wrapping the oven? Does that alter the insulating performance?
Your dimensions are very similar to mine, which is also double-insulated.
No, you should not compress the insulation, because as you wondered it will alter the insulating performance. The stucco is there in part to keep water out of the insulation, and in part to keep it from being compressed.
Your best strategy here would be to make sure your chicken wire (wire mesh matrix) is pressed down all around the insulation—not too tight and not too loose. Any wire at the bottom that is sticking out or bowed out will result in the stucco also being bowed out.
I can confirm that it all fits on the slab, with about an inch margin to spare. And your oven will perform superlatively with a double layer, so it’s totally worth it. After my most recent bake, I did another retention test and found that the interior was still warm enough to bake bread 18 hours after the fire went out.