Permaculturing in Portugal

One family's attempts to live in a more planet-friendly way

Batch Rocket Mass Heater Experimentibuild

Rocket stoves and their DIY construction have been an area of enthusiastic development in natural building circles for at least the last 30 years. They not only offer self build potential, but can be super-efficient forms of heating. The batch rocket mass heater is the most efficient form yet.

Course dates


During the last decade, largely thanks to a handful of tireless experimenters and engineers, rocket mass heaters have become very much more sophisticated, reliable and efficient. Formulas have been worked out to determine optimum performace characteristics, materials refined, temperatures and airflows measured and computed, designs tweaked … so that, while every construction still has its unique variables, the whole process is much less hit-and-miss.

Mostly …

This course/workshop continues in the grand tradition of DIY rocket stove experimentation. We are going to build a batch rocket mass heater for the classroom in the communal building at the quinta, but we’re going to do it in a configuration which, to our knowledge, hasn’t been tried before, so this is also an experiment. We’re going to build a test configuration, see if it works, tear part of it down again, add the heater core, and then rebuild according to the results of the test.

Batch Rocket Mass Heater Experimentibuild

Model of the heater for the classroom

We’ve run the design idea past some of the luminaries of rocket stove experimentation and development and they’re split in their opinions. Half say there’s no reason why it shouldn’t work so go for it and report back. The other half say it’s not going to work. We intend to find out …

So this is a chance for learning not just the principles of mass heater design and function and how to construct one, but to play around with how they can be pushed design-wise, evaluate the various aspects of resulting performance, and then correct it.

Participants will learn …

  • the principles of design and function of masonry/mass heaters
  • the principles of ‘free gas movement’, the Russian-pioneered revolution in the design of traditional masonry stoves
  • the essential ratios in sizing and designing a mass heater
  • the construction of the heater core, the ‘engine’ of a rocket stove
  • cob construction
  • using cob in stove/heater construction
  • the construction of the ‘bell’, the heat-retaining structure of a mass heater
  • cob and earthen plasters as render for interior walls



Batch Rocket Mass Heater Experimentibuild

The site for the heater in the classroom


No previous experience or skills are required for this workshop, though a practical, hands-on approach and a love of mud helps – it will be extremely dirty work!

Registration is limited to a maximum of 8 students. This smaller class size ensures more individual attention for each student, a more intimate group dynamic and, most importantly, room to work on the construction and see clearly how it’s being done.

The particular challenges of this mountainside location mean the course is unsuitable for people with mobility issues and we don’t recommend you apply.


The main part of the workshop will be taught by Wendy Howard. The rocket heater core and its construction will be taught by Floris Winkelmeijer of Batch Rockets Portugal, our (very) local cooperative of enthusiasts which builds these stoves all over Portugal.

The course/workshop will be taught in English.


The Batch Rocket Mass Heater Experimentibuild will run in the summer of 2023. Dates are yet to be fixed, but if you’re interested in attending this course please contact us and let us know what dates would suit you best. We’ll try to reach a acceptable compromise for everyone.

The course is predominantly practical, though the relevant theory behind the workings of batch rocket mass heaters and cob building will also be taught.

In addition to the information given in the course itself, students will also have lifetime access to the quinta’s new online Student Forums with an ever-growing library of natural building-related resources, Q&A forums and the opportunity to keep in touch with fellow students.

The first part of the course will consist of building the experimental configuration of the ‘bell’ part of the stove, then testing it. We then take part of it down again, install the rocket stove core, then rebuild the bell according to the results of the experiment.

Cob building has it’s limitations. Free-standing cob structures need to be allowed time to dry down as we build so they have the structural strength to support the next ‘lift’ of wet cob. With 8 participants plus instructor and volunteers, we will likely have times when we’re forced to wait for the cob on the stove construction to firm up. While we wait, we will do some cob and earthen plastering on two other walls in the classroom.

We work Monday to Friday. Weekends are kept free for arrivals and departures and for exploring the area or enjoying the many other events and activities which go on here throughout the summer.



Batch Rocket Mass Heater Experimentibuild 2022

Mixing cob


Please see the Accommodation page for details.



At the end of the day, you can swim and relax at the river beach in the village below the quinta, take advantage of the free wifi at the open air café nearby, explore the area, meet the locals and other eco-residents, get involved in Benfeita events and generally experience life off grid in a still-beautiful mountain landscape, even though it was decimated by fires in October 2017.

Batch Rocket Mass Heater Experimentibuild 2022

Benfeita river beach


€650 camping (please bring your own tent or camper van). The deposit payable at the time of registration is €80. The balance will be due on arrival.

Caravan supplement is €100/week. The rate for the caravan is the total rate and is the same regardless of whether 1, 2 or 3 people occupy it. The deposit is €15/week, also payable at registration, with the balance payable on arrival. (See Accommodation for more details.)

Prices include all meals. Please be sure to let us know of any special dietary requirements on the registration form.



Because of our small class sizes, our courses tend to fill up quickly. We do maintain waiting lists, but once the courses are advertised as full, it becomes much more difficult to find people to replace cancelled registrations, particularly the closer we get to the course dates. So please note that if you have to cancel for any reason other than government-mandated restrictions on travel we will refund 75% of your deposit provided we can fill your place. The refund can only be made once we’ve done so. Should travel restrictions prevent you attending, we will refund your deposit in full.

We make learning opportunities and the facilities at the quinta available in good faith, but at your own risk. Accidents happen so please make sure you have adequate and appropriate health and travel insurance and are covered against injury to others as well as yourself.

Batch Rocket Mass Heater Experimentibuild

Cob construction

Getting to Quinta do Vale

See the Getting here page.

We will send out everyone’s contact details prior to arrival so participants can arrange car shares and pickups for getting here.

Should you need to be collected from the nearest long-distance bus stop at Catraia de Mouronho, which is half an hour’s drive from the quinta, we ask for a contribution of 15€ per journey.



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