How to make sandwich tubes correctly.
"Sandwich" - the pipes consist of three main elements:
- outer tube;
- inner tube;
- interlayer of mineral wool.
One pipe is in the middle of the other, an insulating layer is located between them. Due to this sealant, the outer tube is practically not heated, in addition, the mineral wool is not burning, and can not become a source of ignition. Such a simple design ensures greater reliability and durability of this chimney. So there is reason to think about how to join the sandwich-pipes on your own, and install such a system of smoke removal on your site. 
With its efforts to make a chimney from a "sandwich - pipe" is quite simple, and materials for this will take quite a bit. As a material for the inner pipe we take a simple stainless steel, the outer shell can be made of any material( copper, brass or galvanized iron).We wind the stainless steel pipe with a heater - basalt or mineral wool, and insert it into the outer pipe. Sometimes you have to put the outer layer of several pieces. Then you should pay special attention to their attachment to each other. To form joints, you can use self-tapping screws or fleas, and also connect individual components, not just the length of the pipe itself.
Also worth paying attention to the temperature of the smoke output, if it is relatively low, as a heater can be used conventional mineral wool. If it is planned to heat the house with a fireplace or a stove, which is heated with coal, it is necessary to take basalt cotton wool, because it can withstand a larger temperature regime. Also, the width of the inner tube should be significantly increased so that its walls do not quickly burn out at high loads. 
The best and cheapest material for the manufacture and installation of sandwich tubing on the countryside is stainless steel. It is not subject to atmospheric effects and will serve for many years without collapsing.
How to install a pipe sandwich.
After self-manufacturing requires the correct installation of the pipe - "sandwich".It should be taken into account the fact that the temperature is very high at the branch of the outlet pipe to the heating device. Therefore, it is necessary to isolate this part very carefully and carefully. It is necessary to equip the structure in such a way as to be able to replace the burnt out area without disassembling the whole chimney. When the pipe is inclined, it is necessary to install a special condensate drain cock, which can appear with a large temperature drop. 
With the standard vertical installation of the chimney, follow the instructions below:
- the inner shell with the bell mouths upwards, in this way the condensate can not pass out;
- we collect the outer tube on the contrary - with the funnels down, with this installation smoke will not penetrate into the middle of the room. This technology is called "Smoke Mounting".
In order to prevent the possibility of fire, it is necessary to insulate the pipe from the ceiling. To do this, you can use the same mineral wool or special hollow boxes of heat-resistant material. Correct installation of the "sandwich" pipe will save unnecessary trouble in the future, and exclude the possibility of a fire. You can also use a steel sheet nailed to the ceiling at the outlet of the pipe outside. In this case, this will provide an additional source of heat in the room, since the metal is perfectly heated and retains the temperature for a long time without melting. When connecting the "sandwich" pipes, take care also of sealing these joints. For this purpose, a special furnace sealant based on sodium silicate is suitable.
Installation of a "sandwich" - pipes on the roof.
When installing the external part of the chimney on the roof, several factors should be considered:
- , when burning solid fuel, sparks are rising up the chimney, and there is a danger of ignition of the roof coating;
- in strong wind, combustion products can settle on various surfaces, including washed laundry, and this should be taken into account when placing laundry ropes.
In any case, the height of the pipe should be sufficient to avoid the likelihood of a fire and save other troubles.