What are the advantages and disadvantages of implementing an outlet of a kitchen exhaust hood through a chimney or directly through the outer wall of the house? There are unused chimneys in the house but there is not a hole to one of them at the right place in the kitchen.

I think there could be differences in these parameters:

  • heat leakage (the house is insulated by polystyrene foam boards from the outside)
  • staining of the house wall
  • complexity and price of the maintenance
  • difficulty and price of the construction

If the chimney will be unused is it worth to enclose the open top end because of lower heat leakage and easier maintenance?

2 Answers 2


A hole in a wall is less likely to leak than a hole in the roof. Furthermore, when a hole in the wall leaks, it is likely to produce fewer problems than a leaky hole in the roof.

In the future, during reroofing, unused chimneys might be removed, and the associated hole in the roof along with them.


If the chimney is really unused, that would work... but you'd be setting yourself up for a safety hazard if the chimney is ever used again, since combustion gasses could back-draft through the vent. Bad Practice, I think.

  • Maybe chimney is not the right word. In Czech Republic where I live chimneys are used both for combustion gases exhaustion and ventilation (but not the same chimney for both). I think that there are pretty strict regulations for chimneys being used for combustion gases exhaustion. ------ In the past chimneys were certainly being used for kitchen exhaust hoods but I have heard that nowadays it is preferred to make a hole to a side wall of the house instead. I am wondering if there are reasons to make a new hole to the house. Nov 3, 2014 at 14:12
  • Chimneys are not just for fireplaces. Any upward vent through the roof for removing the products of combustion serving a fuel burning appliance is a chimney.
    – user23752
    Nov 3, 2014 at 14:52
  • Here in the US, "chimney" in the context of housing almost always means combustion exhaust -- fireplace, heating system, water heater, or other. You certainly wouldn't want that connected with ventilation. Even a ventilation chimney might not want to be connected to a kitchen exhaust, since that could result in sending the fumes you want to exhaust into other parts of the house. Sending the exhaust directly outside is probably a better solution.
    – keshlam
    Nov 3, 2014 at 15:10

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