fire box: insulated fire brick or not?

Hello everybody.. My first post here, albeit I've spent a good few hours reading lots of the information on these boards.

I'm slowly putting together the plans to build a batch box RMH with a bench  attached. There seem to be so many variables to take into consideration.

Anyway, I've found what seems to be, a very good source of refractory materials here in Spain, and am getting close to making an order.. here's a link to the suppliers if anyone is interested. http://tienda.alfran.es

So, my first question is, what do you guys consider is best material for the fire box. Insulated firebrick or uninsulated? Or, a combination of the two?

Many thanks to everyone who posts their experiences and advise!!  

Marcus in Spain

Marcus, if you plan to replace the firebox easilly,  use ifb. Except for the firebox end where the port is. Too risky there. It's not absolutelly necessary. But it works better.

See if they have high density 2600•F insulating firebrick. It’s about 4 times stronger than regular 2300•F insulating firebrick. (Sorry, I don’t know the metric conversions off hand.) Use if for the bottom 9” of the left, right and rear walls and use regular insulating firebrick for the next 4 1/2” of the firebox. Then use ceramic fiber board insulation for the roof.

You only lose about 1/3 the insulating value of regular insulating firebrick but this denser insulating firebrick has 4x the strength and seems strong enough for the left and right hand and rear walls and the port. Use regular dense non insulating firebrick for the floor though, as it gets the most abrasion and abuse from loading firewood. It seems a decent compromise to decrease mass and maintain insulating value for the firebox build but I just picked some up last week so I don’t have long term test results yet. The upper walls and the roof maintain the highest insulation values for the rising heat inside the firebox.

If they don’t have the HD 2600•F insulating firebrick I would still build the walls out of regular insulating firebrick but line them with regular dense noninsulating firebrick splits.

Our local insulating firebrick manufacturer offers 24”x9” bricks, which can be cut easily with a saw and make fabrication of the firebox very simple. You could ask them if they’re able and willing to make this size available.

Thanks guys for your advice! Sorry for the late reply, but jeez I'm running flat out here!! :P

Anyhow, yes it seems they (the suppliers) do have the denser 1400deg insulated bricks. so that's a bonus!  

I've been looking at Peters webpages and like his designs very much.. So I'm probably going to follow one his plans and maybe add a few tweaks along the way..

I really want to get on with this but, like I said I'm so crazy busy, so I don't have time to reinvent the wheel and tbh don't really see the point at the moment.

I just want to build something that works with minimum fuss and bother!! :)

Cheers and all

Marcus

Marcus, use Peter's plans. As is. Don't reinvent the wheel.

You can change slightly the depts of the firebox. Merely the width and height. Don't touch the port, P channel etc. Riser height is  changeable slightly too. As well as the gap.

Satamax Antone wrote:Marcus, use Peter's plans. As is. Don't reinvent the wheel.

You can change slightly the depts of the firebox. Merely the width and height. Don't touch the port, P channel etc. Riser height is  changeable slightly too. As well as the gap.

Yes Peter has certainly taken a whole heap of 'trail and error' out of the equation.. Thanks for that sir!!

I've just been looking again at the batchrocket.eu pages and see he also uses the floor channel secondary air intake system, which he says is inspired by Matt Walker, who in my opinion also makes awesome stoves..
So maybe just a little 'tweaking' is just part of the journey!

Trying now to get my head around how much and of what to order.. shame I don't have a local supplier, who I can just nip round to if I miss calculate on the quanties..

All the best

Marcus