What type of RMH would you recommend?

Dear Permies, people, fellow human beings, creatures of the day who need shelters during cold seasons.

We moved to a new old house built in the sixties (not isolated, old windows), where we will live for 2-4 years.
To reduce heating costs, for general cosiness and to start gathering experience, I am considering to build a secret RMH. Secret because we are currently living in a most expensive area of Switzerland where everything is complicate and.... of course expensive.
So I would find somebody who would secretly drill a hole into our house wall for the exhaust and do the rest on my own.(houses will be demolished in 4 years anyway)
I have to add that I am extremely busy with work, kids, household etc. and that I have got to use my energies, resources wisely in order to keep our family shipping going into the desired direction.

So before I buy any manual, I would like to ask you RMH experienced people for recommendations (please).

Our House: two stories basement. old oil heating system built in the sixties, bad windows.
For our winters I won't expect more then minus 10 degrees celsius (14F)

I am wondering if I can camouflage the RMS as a piece of innocent furniture and the outside part of the exhaust as a bird house ( vaping birds, you know?).

The removing of the RMS should not be too complicate as even getting rid of stuff is very costly here.

And The RMS should of course work well, be save and reduce our heating costs.

On the photo you can see our main living room where I would like to build the RMH.
I was considering as well to just exchange one of the small upper windows (left or right of the terrace door) with a board or metal peace (with a hole) for the exhaust. (so no secret core drilling).
(see foto)

I Prefer to recycle and buy used things to build my RMS, if it doesn't complicate the constructing too much.
I For the mass something that is easy to remove and dumb once we move would be great. (was also thinking of deep soil with I could dump back into the garden I took it from).
Easy to move pebbles would be great too.

What do you think?

Wat type of RMH (from which manual) would you recommend?
Thakyou very much in advance for any advice.

Greetings from Switzerland
Aaron

Hi Arron;   Welcome to the wonderful world of rocket science!
Question)  Are used clay bricks readily available? How about new ?  In the US new bricks are -.50 each at home depot.
They would be your best choice as a mass. Also very stylish in your living room.
Going out a window will work for an exhaust BUT... any chimney outside the home must be insulated or you will not have a good draft.
Question) Are you familiar with the different styles of rmh building?  I.E.)   J tube or batch box? Do you know which you prefer?
Were you wanting a bench to sit on or a bell ?
How old are your children?  Do you have pets (cats) ?
A J tube style rmh has an open hole to the fire. Small children can drop "things" into the fire... imagine a barbie doll ....
A long hair cat could drape its tail in the fire... really bad.... then run about the house...
A J tube also generally uses a barrel as part of the stove... hard to hide a 55 gallon barrel in your living room in upscale Switzerland!
A batch box stove  is more traditional, in that the fire is sealed away from young hands or cat tails... However it is much more complicated to build.
It is usually all brick construction and has a traditional look that most people find pleasing.

Here is a link to a Master builder.  Matt sells detailed plans to build his stoves, he also sells a prebuilt J tube (core only) and Matt gives as many phone/internet consultations as you need as part of the cost.
His stoves are outstanding !    http://walkerstoves.com/index.html

Hello Aaron from Switzerland, I'm Gerry from Canada. Welcome!

Thomas has done a great job in describing the differences between the two main types of rocket heaters, but from your description, it sounds like you may be most inclined towards a J tube style.
The book Rocket Mass Heaters third edition is directed towards those that want to build their stoves from as much recycled or scrounged materials, keeping costs low  and the understanding of how to build one easy to follow.
A functional stove is very simple to build as long as you follow the basic guidelines and not get carried away with deviations that can add a lot of complexity and/or make it not burn cleanly anymore.
Teardowns are even easier as long as you stick with natural materials like clay, sand, straw, clay brick etc. No portland cement should be used especially since you know its not going to be permanent.

They do burn very cleanly but can produce some smoke at times (at startup, when logs get jammed and smoulder etc.) so secretly burning wood is not going to be a guaranteed thing from a potential nosy neighbour who may not like you. I hear brownies helps though.

If you do decide to build one though, you've come to the right place. Feel free to ask lots of questions and post pictures as you get going.

Is the small window near the top of the door where you were thinking of exhausting? How much wall is above that? If you go out the window with a simple vent, you could get backdraft if the wind blows at the wall. That is very not fun, and smoky. How steady is the prevailing wind in heating season? Does it change in other seasons? For reliable operation, you really need to exhaust above the roof, not on a sidewall. A good RMH will give cool enough exhaust to safely (but not legally) run a simple stovepipe up inside the house to a high exit. I would not recommend this except that the house will be demolished when you leave it.

You have a basement; what is the floor like under the big window by the door, or in the corner of the room? A bell style RMH which would be least conspicuous needs a slab base, or strong posts or piers going down to the foundation. For a short-term installation, solid wooden posts could work.

I think a bell less than a meter square by 1 1/2 meters tall could take care of you. Plenty of other configurations are possible depending on your needs. You do have to have some part of it about 1.5m tall. It is possible to make a J-tube and bell completely out of cob, if you have decent clay in your back yard or elsewhere. That would be totally recyclable.  

Hey Guys, thank you very much for your replies!

That is already quite some input for me and I am looking to spend time with checking out the single points, hints, suggestions etc.
(my 3rd child is about to born these days, so it might take some time for me to reply)

greetings and best wishes, Aaron

Aaron, try to check what is the legislation about kachelofens, where you are. A "batch box" is a kachelofen, more or less. I can see houses facing yours. And i'm dubious you would get away without trouble. Exhaust against a wall can be done, if you are absolutely sure that there won't be  a wind gust which will put your fire out, and smoke the whole house. Remember, this could kill.

What i see, is the right hand corner of the room doesn't seem busy. You could fit a bell there. And a U turn bench, in place of the radiator. But, since the wall is not insulated, this is not the best place. Better heat inside walls. Which retain heat inside. And spread the heat to other rooms.

I am partial to batch boxes. J tubes are too finicky for my liking.

HTH.