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Discussion Starter · #1 ·
We just bought a house that we're doing some renovations on. The chimney style hood fan in the kitchen - that was listed as 'custom' - is a joke. It barely moves any air. I had my contractor look at it, its basically a tiny recirculating fan from over an electric stove that they put into an oversized welded hood that somebody made them. This is over a standard 4 burner, 30" Kitchen Aid gas stove. Needless to say we frequently set off the fire alarm when cooking greasy things like bacon etc.

Here's where I'm getting into all kinds of problems. We opened up the bathroom to renovate it and noticed that the pipe that was running from the hood fan to the exterior was actually just that corrugated dryer tube stuff - very much not to code. So it's coming out. Several issues we're now facing.

The size of the pipe and available space. It's currently 4.25". To install a 6" pipe will require us dropping the ceiling. 6" pipe is strongly advised in any hood fan with a CFM over 400. My friend who is an hvac guy strongly recommends 6" for any hood fan. However we also don't have an HVAC or return air system in this house, so we aren't really supposed to go over 300 CFM, although my hvac friend said 400 cfm should be fine in an older home like mine because its not sealed up like a newer home, and I can turn on the furnace fan as an offset.

The cost of dropping the ceiling is what we're concerned about. The contractor is saying it'll add another $1200 or so.
The renos are already going well over budget. We're basically weighing the cost of upgrading to 6" vs keeping it 4". We can't go over a 400 cfm fan - so will we really see a big advantage there? Future proofing is one thing, if we put an HVAC in years down the road I suppose.

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