Rocket mass heater basic questions

Hello permies,

I am considering building a rocket mass heater to replace my fireplace insert (image attached). Before I launch myself in buying the whole DVD set I have a few basic questions on the technology:
- What type of rocket heater/mass heater would be the most appropriate to heat up a 400 sqft living room economically knowing that I live in a mild climate with occasional rare frosts but not in a particularly well insulated house?
- Do rocket heaters only burn small diameter branches?
- Does the updraft make a lot of noise?


Thanks for your insight,

Sebastien

You may want to study batch box rocket stoves as they have largely superseded J tube rocket stoves but both types have independent appeal.
Generally speaking J tubes use small diameter sticks or chopped wood and are relatively easy and cheap to build.
Batchbox styles look more like a wood burning stove with a front door but are correspondingly more difficult  and expensive to build.

In their  most basic form a simple 6” J tube will heat a very large room quite quickly with radiant heat and in a more complex form, store heat for several hours as well.
However they need feeding every 20-40 minutes with smallish pieces of wood, the smaller the wood and the more regular you feed the fire the higher the temps get.  
Batch rockets tend to concentrate more or stored heat and with only a short burn cycle they can offer many hours of stored heat.

To be honest there are so many variables you will need to spend some time studying this forum (and others) before you can expect to gain an accurate picture of what a rocket stove can achieve.

Hi Sebastien,   As Fox pointed out, a 6" system would definitely be big enough to heat your small space in a mild climate. For a first time build, a batch box may seem a bit overwhelming therefore, I would recommend a 6" J tube. Do you have a copy of the Rocket Mass heaters builders guide? I think this book would help you out a lot more than the DVD's as it covers every step in good detail and you can have it open right in your room while your working. To me the video is more of a companion to the book which may help to show some things visually rather than in mostly words from the book. There are also plans that can be purchased by the authors of the book if you think that you need a more precise layout to follow.
The updraft sound you noted is one of the reasons for the name. The rocket or whoosing sound is definitely noticeable (but to me) not annoying in any way. Its rather enjoyable to my ears and can be used as an indicator of when your dragon needs to be fed again.

I'll give a strong recommendation for a batch rocket. I'm biased, having never built a j tube. While I agree that the j tube is simpler to build, I can't say I found the batch rocket particularly difficult to construct. I was offered plenty of excellent and prompt advice here at permies and took my time and I'm very pleased with both of mine.

Benen Huntley wrote:I'll give a strong recommendation for a batch rocket. I'm biased, having never built a j tube. While I agree that the j tube is simpler to build, I can't say I found the batch rocket particularly difficult to construct. I was offered plenty of excellent and prompt advice here at permies and took my time and I'm very pleased with both of mine.

Thanks for your advice. The batch can burn larger pieces of wood than the J tube? Is that correct. Do you know if the builder's guide book also includes a design for a batch heater?

Thanks

Sebastien Duclert wrote:Thanks for your advice. The batch can burn larger pieces of wood than the J tube? Is that correct. Do you know if the builder's guide book also includes a design for a batch heater?

Given the same system size a batchrocket can burn larger pieces of fuel, yes.
There's no design as such in the builder's guide book, but all information is concentrated on batchrocket.eu. In seven languages including Spanish.

Peter van den Berg wrote:

Sebastien Duclert wrote:Thanks for your advice. The batch can burn larger pieces of wood than the J tube? Is that correct. Do you know if the builder's guide book also includes a design for a batch heater?

Given the same system size a batchrocket can burn larger pieces of fuel, yes.
There's no design as such in the builder's guide book, but all information is concentrated on batchrocket.eu. In seven languages including Spanish.

Thanks Peter for pointing me to your website. Great that you share all this detailed info on batch heaters with the world!

Peter van den Berg wrote:

Sebastien Duclert wrote:Thanks for your advice. The batch can burn larger pieces of wood than the J tube? Is that correct. Do you know if the builder's guide book also includes a design for a batch heater?

Given the same system size a batchrocket can burn larger pieces of fuel, yes.
There's no design as such in the builder's guide book, but all information is concentrated on batchrocket.eu. In seven languages including Spanish.

Hi Peter,

Two questions for you: I would like to build a stove in the corner of my first floor which appears to be built with inverted concrete T beams and those hollow blocks resting on top like in the attached picture. It then probably have a thin layer of concrete and terracotta tiles. Do you think that this type of construction would be sturdy enough, in principle, to hold the weight of a batch rocket stove?



Do you know anyone in Spain that I could hire to help me build such a stove?

Thanks,

Sebastien

Sorry, I can't advise you on how much weight your floor can handle.

But I do know about a couple of builders in Spain:
One is called Pablo Bernaola, he lives near Madrid, I believe. His website is http://estufasrocket.es/
The other one is Eduardo Marquina, website is https://estufasdeinercia.wordpress.com/