Chimney Smoke Backdraft into Home Ventilation: How to Prevent It?

Hello, I'm asking for advice...
I have such an unlucky location and construction of my house that when the wind blows, it pushes smoke from the chimney into the ventilation holes on the chimney...

The unfortunate thing about the structure is that the fireplace chimney is above the garage, which is attached to the "house proper - the residential part"

The chimney is very close to the junction of one roof into another... I have a theory that when the wind blows, it compresses the surfaces of the roof and spreads in all directions - falling into, among others, the ventilation grates that are on the sides of the chimney.

There are no "vents" installed at the top of the chimney yet? - smoke comes out directly from the hole at the top of the chimney.

What can be done to avoid such situations?
I will add that after observing the smoke coming out of the chimney, it looks like one big smoke ball - it expands in all directions.
In the second picture, I marked in red the channel through which smoke flows into the grate in the kitchen - where, fortunately, I have a hood. If I forget to turn it on, smoke starts coming in there when there is a stronger wind.

Also mark the path of the escaping smoke - it will be more transparent, your description shows that the chimney is right next to the vent. Be more specific about it.

I have two suggestions:
1. Raise the smaller chimney to the large one. It doesn't have to be brick, just a pipe.
2. Hood motor speed controller (less energy consumption). The engine rotates constantly, but slowly enough to prevent smoke from entering the house. Alternatively, a computer fan and a simple power supply.

The smoke escapes through the combustion pipe, which runs parallel to the ventilation duct marked in red. The stove is in the garage, at the foot of the chimney, if I may say so.
As a result, smoke from the chimney flies out just above the outlet of the vent duct.
When a breeze blows, the smoke "rolls up and curls into the vent."

I would not like to significantly increase the smoke outlet by inserting, for example, a sourdough pipe into the outlet of the furnace channel

Added after 3 [minutes]:

Now I came up with an idea to control the fan speed based on the wind force sensor - if the wind blows, the engine speed would immediately increase.

But apart from the solution - what is the reason for this?
Extending the chimney with a pipe is perhaps the only effective solution because the smoke will billow higher and will not fall into the grates on the chimney. Anyone else have any suggestions?

The only one-time paid method will be to raise the chimney with exhaust gases to a level higher than the large roof and install the so-called fireman.
Read about the rules for building chimneys.

In a sense, there is a design error. Such a chimney should be above the roof ridge for everything to be fine:



You have several options you can try.
One is the replaced chimney extension.
Secondly, it would be possible to abandon the ventilation in the chimney and build only a combustion chimney, and connect the ventilation in a different way.
The third option is to use such a cap, but it is not known whether it will fulfill its purpose, it actually rotates with the wind and the exhaust gases go in one direction, but it is not known how it will work in practice:

I've already read about firefighters on other forums... I won't risk it...
All I have to do is extend the chimney, but I'll wait until spring. (I thought I would avoid it, but it's hard to avoid it...)
Thanks for your replies

In my case, this problem appeared after replacing the windows with plastic ones. For two years I created various miracles and the problem disappeared (in my case) after replacing the regular ventilation grilles with gravitational valves. These are pieces of PVC pipe with a flap inside that opens under the influence of draft in the chimney (in your case, after turning on the hood fan), if exhaust gases flow back into the ventilation duct, the flap closes. I bought these valves abroad because they were not available here (about 10 years ago), here they are now this is also available for purchase. Ask in stores specializing in ventilation. Now some of my advice;
-the flap is always open during airing
- the flap can knock when there is wind (I put a piece of rubber on it and the problem disappeared)
- a visit from several chimney sweepers didn't help (they threw up their hands because everything was fine. )
- in the basement I made additional supply ducts, one to the boiler room and the other diagonally across the building from the boiler room (the first one greatly improved the operation of the boiler)
-the air flowing into the basement is pre-heated and this influences the ground floor
-in the future, I plan to install an air intake in the garden and bury approximately 50-70 m of pipes with antibacterial coating and from this supply the second air supply (the air will be pre-heated by the ground temperature)
-the house is too tight and the air needs to be replaced
I gave up the repercurator for economic reasons
I wish you good luck and lots of fresh, warm air.

I have such a grate in the bathroom - with an additional fan. But this does not protect against smoke or the smell of exhaust gases. These latches are not tight enough to prevent outside air from entering.

I will say this: the accumulation of air is so great during gusts of wind that when I lit the stove yesterday and it blew... it cleaned the stove from the chimney side so much that you can only imagine what I looked like after such an operation... And it blew in from the top of the chimney and not from the side plane... The cross-section of the channel is 15x30 :)


If there is a stronger wind one day, I will light some garbage outside and see from the outside how the air behaves around the chimney and the roof. Maybe I'll think of something else. I will make a small wind tunnel - something like that, so that we can see where the wind bends on these roof bends. Maybe an option would be to move the grids lower...
Anyway, I'll keep trying.

Added after 3 [minutes]:

Ultimately, there is still the idea of installing an anemometer on the chimney, which will turn on the fan in the bathroom and the hood in the kitchen when there are wind gusts, of course in series with the sensor whether the stove is lit. and in parallel with other switches for the hood and bathroom fan
Greetings

Jaromisz, you think like a horse uphill. Just extend the exhaust part and the problem will disappear.

The magister is right. There is no point in elaborating further. I'm closing the topic.