First-timer requesting advice for difficult installation in Japan

I apologise for my extreme ignorance in advance, but am hoping for any practical advice on a big Dutchwest 2479 woodstove (that has a 152mm flue-exit/flue-collar diameter) to connect to 106mm stovepipe with an adapter, venting to an existing outside chimney, which is has a diameter of about 180mm.  The stove was a gift, and very limited finances mean that everything is DIY with used, recycled, reclaimed materials.  We live in the countryside of northern Japan, where kerosene stoves are commonly used with 106mm stovepipe connected to an outside chimney.  The chimney is on the windward side of a two-storey house, looks to be concrete enclosing a ceramic chimney, with access for cleaning from a small outside gate at a height of about 60cm or so.  

One of the issues is that the hole in the wall where the stovepipe connects to the chimney is 106mm - much smaller than the Dutchwest 152mm.  Rather than increasing the diameter of that hole in the wall, we would like to use single-wall 106mm stovepipe.  What are the risks of using a much smaller stovepipe for a big stove?  We might insulate the 106mm stovepipe ourselves, as a local friend has done successfully, and someone on this site also posted about that.

Another issue is that the water mains are right out in the kitchen, just below the chimney connection point.  People don't heat empty houses here, and turn their heaters off at night, so if they're going to go away for more than a day, or it's going to be an extremely cold night, they turn off the water at the mains and drain the pipes.  The lever to turn off the water is about 90cm in height.  The water pipe to supply the bathroom goes up the wall, near the stovepipe.  There is only 170mm clearance to some plastic parts on the plumbing to the right, 315mm to a wooden cupboard to the left, and only 295mm between the current 106mm-diameter stovepipe and the ceiling.  What kind of heat shield, if any, would work in this small space - for the ceiling and all three sides?

Another issue is that the horizontal run of the stovepipe would be 1800mm or so, after an initial vertical of 1200mm.  That would involve two 90-degree bends, plus a 45-degree joint in between because the chimney is in the corner of the room and the stove is in the middle.

The current chimney also vents a kerosene hot-water boiler in an unheated area on the other side of an uninsulated wall, connected with a T.  Potential problems of draft & toxic fumes mean we might have to find a new way to vent the hot-water boiler without using the current chimney, although some local knowledge says that this type of outside chimney can work really well for woodstoves, so draft might not be a problem. Would lighting some newspaper from the outside cleaning gate help warm up the chimney to create draft, if it seems to be an issue?

The stove just got put in the house yesterday, in the middle of the kitchen.  There's enough firewood for evening use for four to five months, but the stove won't be firing most of the time and the chimney will definitely cool down.  Very rarely, temperatures can go as low as -20C, but it's usually -5 to -10C.  The incredible amount of snowfall provides an insulating layer on the ground, so the frost level is only 60cm, and the snow accumulation blocks the little gaps in the foundations of this drafty, poorly insulated house.

The top down fire-starting method (also first lighting lots of loosely bundled newspaper on top to try to warm up the chimney) seems like it might help improve draft.

We're going to give it a go and be prepared to call it off & just rely on the kerosene heater with warm baths to warm up (Japanese style) before going to bed with a hot water bottle, but any quick constructive responses with suggestions to make it work would be greatly appreciated!    Thanks to any of you who actually read through all of this!

If a stovepipe is too close to something you don't want to overheat, one easy way to protect it is with a piece of aluminum foil strategically placed between the hot pipe and the surface you want to protect.  It should be suspended between the two and not in contact with either.  It will act as a heat reflector and the vulnerable surface behind it will stay nice and cool.  For the water pipe shown you should be able to contrive some wires hanging from the stovepipe to hold a piece of foil horizontally below it.

Thank you, Alder!

boy that is a tough one. I can think of a few ideas. I don't like the dual purpose chimney that is intimidating id want to split them. Keep at the larger diameter stove pipe until just before you hit the reduction. Make sure you have the ability to visually check the clay chimney. Try to burn only the driest of wood and keep the fires modest in size and feed them more often; no loading it up for the long slow burn. Keep a big pot of water on it at all times for mass and hot water.
Late night musings...
Cheers,  David

Thank you for your reply, David.   I kind of guessed that if increasing the diameter generally reduced draft, then reducing the diameter would increase draft, and the nearer to the warmth of the fire, the better the draft might be, and the better the draft at the start, the better it would be along the whole length of the chimney.  Bad logic?  It seemed simpler to go with the 106mm stovepipe directly from the stove all the way to the 180mm chimney.  

I just connected what we inherited of the Dutchwest 152mm single-wall stovepipe (which we thought we wouldn't use) and it rises 900mm to a 90-degree elbow, and we have another 620mm length of pipe, but it looks like it might need an angled adapter to make it incline enough to make up the small difference in height to the current hole in the wall which is 106mm in diameter.  A slight incline is slightly better than horizontal for draft, right?

If we used 152mm single-wall stovepipe to the wall and then used a reducer to make it connect to the 180mm outside chimney, would that not form a kind of choke, having a sudden reduction in diameter from 152 to 106mm and then a sudden increase from 106 to 180mm at a 90-degree connection, which is essentially outside in the cold?  I'm new to all these concepts, so have no idea what would work best.

We plan on keeping the fires modest in size for safety reasons and for lack of firewood!  We managed to get some pretty dry firewood last-minute, and, if necessary, will split the rest even smaller and dry it near the stove as long as necessary or just save it for next year.  We don't want to walk around in t-shirts, barefoot; we wear thermals & lots of layers, warm hats, socks & slippers, and play hackysack to keep warm to reduce our consumption no matter what the heating source.  I'm a big advocate of using the thermal mass of water, so plan on having a good supply on the stove, and then transferring some of it to bottles to put in a 'cooler' (insulated box!) to keep warm until the stove gets fired up again.  We're more early-to-bed-early-to-rise kind of people, so it'd be evening musings for us, but we live by candle- and lamp-light, so it always feels later than it is!

Many thanks for your thoughts.  I'd be very interested to hear what you and anyone else thought about my concerns about creating a 'choke' at the wall where the horizontal stovepipe would meet the vertical chimney outside.  I suppose that would be easy enough to clean from the small gate outside near the base of the chimney, if any creosote built up, but how might it affect draft?  There are so many questions.  I really appreciate the sharing of knowledge and experiences on this site.  Thanks again!

Hi Liz;  Welcome to Permies!
  I think if you are careful you could make that junction work. The sharing of exhaust with the water heater is my main worry . Hanging a sheet of metal or the foil would deflect the heat from your plumbing. But there is a chance your heater would try to vent into the wood burner (if it is out) and then vent inside your home... not good.

Do you own this house or at least have permission to modify things ?  If you could run a full size pipe from the dutchwest stove directly to a window you could replace the window with a sheet of metal and put your stove pipe through that. I have seen this done many times , when people do not wish or were not allowed  to install a roof jack.

If you do go with a joined chimney , I think that it would be better if the dutchwest was reduced in diameter at the stove rather than up at the chimney.

Another  factor you may not have considered is that a nearly horizontal pipe will collect creosote and that will find a way to drip inside your house... even if you were to tape the joints with a metal duct tape.  Very messy & hot if it lands on bare skin.

Some food for thought..... On a completely different track, if you have room (I suspect not) have you looked at rocket mass heaters ?  They can be built small, they can be built very cheap (clay mud rocks maybe some bricks)  , If your wind is consistent from one direction a rmh can be vented horizontal if it exits on a windless side.  Also uses small wood ,quick hot fires , NO creosote,  almost no ash, no smoke out your chimney, NO FIRE ALL NIGHT! toasty warm mass to sleep on or next to...  They are so much better than a standard wood stove that they should be the ONLY wood burner allowed !   ha ha fat chance the main stream would accept that!
Good luck with what ever you decide to go with.

Thank you for the warm welcome and advice, Thomas!

We are concerned with sharing the chimney with the water heater, but are just going to give it a go.  If it became an unmanageable problem, we would use the standing outside chimney for the woodstove and open a small hole in the external wall to vent the water heater.  

At this point, we are planning on reducing directly at the stove with 106mm single-wall stovepipe.  We may insulate the stovepipe at a later time, if it seems worthwhile.

We are concerned about creosote with the long horizontal section of the stovepipe, but used this stove with a long horizontal stovepipe without problems for many winters where we lived & worked in a nearby area.  Of course, that was with a different stovepipe, different firewood & firewood storage, different chimney, different building, different area, different elevation with different (more extreme) weather, so we will just have to give it a trial run to see how it all works in various conditions (wind, outside temperature, air pressure, etc.) The building where we wintered has been demolished and the owners gave us the stove, so that's how this giant came to us!

We rent this house for a very nominal fee from the owner's cousin, who lives locally, on the condition that we fix whatever needs fixing, and have permission to modify as we like.  The idea of a rocket mass heater is very appealing, but a bit daunting.  We have never built anything like that nor even seen one in person.  A few people we know use rocket stoves to cook outside in summer, but we know of no one who has built a RMH inside.  Even if we learnt how to do it from reference materials alone, they must be very heavy, so we would need to build a support system under the floor, which would be a challenge.  The house has a concrete perimeter foundation with concrete base stones placed directly on the earthen base at regular intervals to support the structure.  The crawl space is very cramped and not ideal for constructing the major support structure we would have to build.  There is only a very small access point in the kitchen floor, so everything would have to be assembled in the dark crawl space.  The earthen base is not perfectly even and wouldn't provide a rigid base, so to accommodate for settling over a large area seems a bit beyond us.  (Although we did build a very small support base for the big woodstove with a thick beam, two legs, and two car-jacks!)

The wind generally comes from the west and we are sheltered by mountains and woods, except during typhoons and very rare extreme winter storms when it usually comes from the east and there is less protection with only a few smaller mountains to shelter the house.  If we were to vent horizontally, the snow accumulation would be a big issue.  If we built a RMH, which is unlikely at this point, we would most likely have to vent it out the standing two-storey chimney.  

If we knew we were going to stay in this house permanently, we might make the effort, but we have dreams of getting a bit farther away from the local agricultural pesticides and building our own straw bale house, so are currently just making do with what we have.  A RMH seems a long way off, unless anyone with experience & motivation happened to turn up on our doorstep at the right time!

Thank you, everyone, for your thoughtful advice and taking the time to write!

You keep describing this stove as "big"... how much oversized is its capacity relative to your current heating load? Is your current residence smaller than the house where the stove was previously? The greater the disparity between stove capacity and load, the more you will have to burn slow and dirty to avoid overheating the space. If you can put extra firebricks inside the stove (walls, floor or ceiling), you could reduce its capacity to closer match the load, and also have some mass to hold heat while the fire is out. Any bricks or stones you can fit around the stove will also add mass and temper the heat output.

A bench-type RMH can be built without major reinforcing if the floor is already good, but the photo tends to indicate that there is not space for a horizontal mass. A vertical bell RMH which would take similar space to the wood stove would definitely require its own footings. If you don't need to heat the whole house all day and night, you might find that a small version of RMH is feasible, in terms of space requirement, footing needs, and wood consumption.
https://permies.com/t/71576/tiny-house-rocket-mass-heater

Hi, Glenn.  Thanks for the great suggestion to put extra firebricks inside the stove.  We had considered that before, but were concerned about affecting the airflow for the secondary combustion chamber.  We were also given a fair bit of 60cm lengths from a friend whose stove could only handle 45cm, and didn't want to have to either cut those logs again or not be able to use them by reducing the size of the interior of the stove.  Would even a few bricks placed strategically be worthwhile?  We don't want to block the airflow from the base grate, but could possibly fit some at one end.

I would like to have a brick or stone (or cob) heat-retaining wall surrounding the stove to act as seats, warming areas for cooking vessels, etc, but we don't have much space, and that would increase the weight on the floor, so we are giving that a miss for now.  The house, as a whole, is not tiny, so we could open all of the interior doors to let the entire house warm up (unheard of to this point!).  

Again, the RMH is very appealing, but since we have this stove in the middle of the kitchen, and the snow has started to fall and probably won't melt until April, building a RMH is not an option this season.  We also have extremely limited finances, so buying any materials takes a lot of consideration & time to find something within our budget.  I'll have a look at those plans for future reference, though; thank you for posting the link.

By the way, the stove used to be in a lodge with seven bedrooms, but was not the only heating system, so it will be interesting to see how it fires up here.  This is going to be a big experiment, no question about that.  It is also not ideal, but it is what it is, so we are going to try to learn as much as possible from the contributions everyone has kindly made here, and not rush to fire it up.  We still don't have the reducer and other parts for the chimney, are still considering whether we should insulate that stovepipe or not (but will probably just insulate the last section to let the heat radiate from most of the stovepipe to warm the room(s), but then also try keep it warm before it connects to the outside chimney), and are seriously looking at giving the hot-water boiler its own vent.  

It's going to take a good while to do all of this, so if anyone has any food for thought, we are very keen to learn from your ideas and experience.  We really appreciate the time & consideration all of you have taken in reading through this and writing your comments.

Do logs go straight in, or parallel to the front/door? Even if you just add firebricks at the sides of the logs and leave the length dimension alone, I think it would help. Every brick or stone you place near the stove, or under or on top of it, will help some in tempering the heat delivery.

There are two doors.  We use the wide front glass door for easy set-up, but then feed the fire from the narrow side door.  We will see how it burns and then consider whether we should add bricks inside or not.

The whole thing is on the back-burner for the moment, with other things taking priority, but we are planning on making a reducer from one of the shorter lengths of the original stovepipe.  If anyone has done anything similar, it would be interesting to read any suggestions or thoughts about this.