retrofit range hood idea
My house has a recirculating range hood. I’ve been mulling over different ways of implementing a proper one. I plan to keep it under 300cfm, but my house is very tight so I’d still want to provide makeup air in some fashion. Simplest option would be opening the kitchen window, which is about 5 feet away on the same wall. Is that far enough to avoid short circuiting? There’s also the option to switch the ERV exhaust fan off when using the range hood. The control is in the kitchen, so it wouldn’t be that much of a chore. The ERV is capable of about 250cfm.
My question has to do with the hood itself. My idea is rather than just adding a duct to the current range hood, I’d put in an 8″ ECM blower right in the duct. The duct can go straight out the wall, and the wall is plenty thick enough to accommodate this configuration. The benefit is that it would be much quieter and it can be fine tuned for flow. I already have the blower that I’m not using for anything else, so that part would be free. Any compelling reasons not to do this?
Also looking for suggestions for best/simplest airtight way of closing this off when not in use. Something wired into the fan control would be ideal.
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Replies
Trevor,
Inline fans are a great idea for range hoods, as I suspect the most common reason they don't get used during cooking is noise.
Fantech sells hoods with no fan: https://www.hvacquick.com/products.php/residential/Kitchen-Exhaust/Kitchen-Exhaust-Kits/Fantech-Kitchen-Ventilation-Kits
I was hoping to just remove the integral fan in the hood I have. Is there a reason not to do that?
Trevor,
No reason I can think of.
Disabling the ERV exhaust fan can cause your core to freeze up in the winter time, I would not do it unless you have a way to bypass the core. If you find you need makeup air, go for a passive intake with a motorized damper tied to your range hood switch.
Motorized dampers tend to seal much better than most range hood flaps, you can install a one in line with your exhaust fan.
Make sure you plan for a way to access the fan and damper down the road as cooking grease will coat everything. Over time this can cause fans and valves to stick.
I have a ground loop preheater, so the incoming air is always above freezing.
Not a fan of the passive intake as it's yet another partially leaky, uninsulated thermal bridge 24/7. Plus running wiring to it from the range hood control area would be a pretty big pain.
I was planning on putting a filter in front of the fan, but obviously having the fan accessible is important if for no other reason than it might need replacing at some point.
Sounds like you have a perfect situation for using the ERV with the exhuast fan off. The ground-loop preheat will be beneficial for that makeup air.
Filter in front of the fan will clog in no time. A hood with decent grease baffle is about the most filtering you can do.