RMH Bed Warmer

I've been thinking through the applications of the rocket mass heater.
I probably don't really have a NEED for radiant warming, as I'm in a climate where it goes below 0 Celsius maybe once in the winter, and only a couple of days.
I'm in the process of building a half in the ground house, which will require digging down a foot or 2 to build a bed platform, and probably 3-4 feet for a gully to stand up straight in.
The only time I'm really hoping to crawl is into bed.

So my Wishlist item is a rocket bed heater.
Since I'm excavation in any case and backfilling compacted earth (with some kind of finish? thoughts now at rammed earth with a linseed/lime seal),
I thought it would be nice to cash in on some permaculture luxury!

Any info on what would be the best way to achieve this would be great!

I've researched as far as realising that I need to build some kind of fire retardant core.

What I'm really wondering about is how long/far the chimney/exhast pipe can go and at what point does it become inefficient.
Also wondering about the lag time between lighting it up and when the heat is absorbed into thermal mass.

The idea is to place a mattress on the earthen platform. On that note, any earth friendly suggestions on mattresses also welcome!

Hello Leigh,   What a wonderful idea that is to make a warm bed to sleep on. One I'm sure you won't regret.

There are two main types of heat extraction systems from a RMH. One is the use of pipe to channel the hot gasses through and the other is a bell system which is basically just an enclosed fireproof space that allows the gasses to stratify and eventually leave much cooler.

The pipe system generally has a limit of 30' for a 6" system and 50' for an 8" system but also is affected by elbows and other factors which could slow the draft down.
The bell system can pretty much take on any shape you wish as long as it doesn't get too narrow which could create a bottleneck and the size is more flexible.

The lag time from fire being started to the mass getting warm really depends on the materials used for the mass (emissivity) and how thick they are.
Trial and error is often needed to help regulate the temperatures and to help alleviate hotspots.
A little more or less mass in some areas or even a bit of insulation can help dramatically.

The RMH in a tipi build at Wheaton Labs RMH-Tipi is a good place to start. I think they used homemade buckwheat hull filled pillows all sewn together for their mattress.

Once you know a little bit more about what kind of build you have in mind, come on back with questions and even a rough picture so we can help you out further.

Hi Gerry,

Thanks for your reply!

I am familiar with the tipi bench, will use that as a point of departure.

I’ve come to terms with the fact that I build rather slowly, so the build (and gathering materials for the core) might take quite a bit of time.

The ideas will be festering in my mind in the mean time. I’m quite excited about living on earth and experiencing the thermal regulation on natural earth.