Rocket Mass Heater at the Green Ossining Earth Day Festival

What amazing day we had sharing information with you about Rocket Mass Heaters! I hope you are as excited about their potential as I am. Below you'll find answers to some of the most frequently asked questions from the event. Jump to the bottom for links to key resources and our contact information.

Frequently Asked Questions

Q: What's a Rocket Mass Heater?

A: From the Wikipedia article:

"A Rocket Mass Heater is a space heating system developed from the rocket stove, a type of efficient wood-burning stove, and the masonry heater. Its fundamental characteristics are an insulated combustion chamber where fuel (generally wood) is burned with high efficiency at extremely high temperatures, and a large thermal mass in contact with the exhaust gases which absorbs most of the generated heat before the gases are released to the atmosphere."

Q: Are they legal?

A: It depends on where you live. Portland Oregon has incorporated rocket mass heaters into their building code, so getting a permit to build one in your home is a relatively quick and straightforward process. Many people use them to heat outdoor spaces in the wintertime, or to heat a greenhouse over the winter to extend the growing season. 

Glenn is in the process of building one in his home in Ouaquaga, New York, and has multiple outdoor installations on his property. 

Niki is interested in building one to heat her home, and is actively raising awareness in her village of Ossining, NY. She is hoping the Village can follow Portland's code as a template, and perhaps be the first city on the East Coast to have a Rocket Mass Heater-friendly permitting process.

Q: Do they always look like this one? 

A: No. The demo Rocket Mass Heater we brought to the Earth Day Festival was built with mostly found/gifted materials. It was designed to be portable and easy to assemble, not necessarily beautiful. As with a fireplace or a sculpture, a Rocket Mass Heater can be built in many shapes and styles, limited only by your patience, budget, and imagination. 

Q: How can I get one?

Rocket Mass Heaters are not the kind of thing one will find at a home depot. They must be designed and constructed appropriately for the particular space and usage desired. The two ways to get one are to A) Do It Yourself or B) Hire someone to help you.

Q: How much do they cost?

It really depends on a lot of factors. First, are you doing it yourself and just need to buy materials? Then it can be done as cheaply as $300. Are you looking for someone with experience to guide you and some of your closest cob-loving friends to build a project you designed? Are you looking for someone to build it for you? There's a lot to consider, but we're happy to share what we know. Contact us using the information at the bottom of this page. 


Key Resources

Contact Us

If you have other questions, want to stay informed about building code happenings, or want to talk to us about a project or idea of yours, we'd love to hear from you!

Niki's email address:, and she tweets as @niki9 and @permietech

Glenn's email Address is