Kas,

Thanks so much for this very educational information. The Duct is 12X4. What is a Vent-a-Hood system, if this is the kind I shall avoid, which kind I shall look into it then? "conventional systems (Broan, Wolf, ModernAire, and many others.) ", correct?

Thanks!

Jane

Do you have permission from the condo association to open up the wall to attach a new vent?

@weedmeister Do I need to? That is inside my unit, and won't affect others as long as I'm not open the other of the share wall, right?

Depends on the rules they have. For most condos I'm aware of, you own the paint on the wall (and the cabinets) but not the wall itself. Hence no wiring or plumbing changes, or wall moving. Nails and screws can penetrate, but not much else. So ask now. They may not care.

Thanks for the warning, I'll definitely check! I do know the cabinets are allowed to remove. Two of the HOA members had that done.

12 x 4 inches is just a bit more restrictive than an 8-inch round duct. I was afraid you might have a 4 or 6 inch duct. With a 12 x 4 duct you should be able to stay within the desirable 1000 to 2000 ft/min duct flow rate with 300 to 600 CFM actual flow. (Blower rated flow needs to be higher, as previously pointed out.) While higher flow rates are possible without seriously adverse effects, staying within this range is considered good for avoiding too much grease impingement on the duct walls.

My point about Vent-a-hood is that their blower design has advantages for their purposes, and is certainly adequate for modest added pressure loss beyond their hood's transition losses, but their blower design is not as good as that of the blower types used by their price competitors when the blower has to force air through long ducts. And we haven't addressed make-up air, which might be difficult to supply with low pressure loss in a condo environment. Added HVAC structures may be difficult to integrate without some HOA violation. You may have to live with an open window when full fan power is needed (e.g., Sichuan cooking).

My goal is to provide the requirements that if met will lead to no complaints about cooking effluent filling the residence or ma-la-wei pungency burning the cook's eyes. To ensure this within practical limitations, I try to be as conservative as practical in the performance dimension. In your case, it is possible that with a Vent-a-hood dual blower arrangement, you would have adequate capture and containment flow rate. But I think it is more of a sure thing to use other hoods and blowers that are sufficiently close to desired qualities of size and flow rate.

For examples of "high end" hoods, you might want to review the Wolf Design Guide pdf available at Wolf's website. ModernAire also has a website with standard hoods described. ModernAire is also noted for building tailor-made hoods for special applications. A huge selection of hoods may be reviewed at ajmadison.com. These will provide an idea of the wide scope of designs, although many seem better suited for appearance then for performance.

I do not recommend specific hoods, but will comment on how far particular examples appear to deviate from the performance efficiency ideal typified by commercial hoods.

kas

Kas,

Thanks a million for the wonderful advise! This had truly come down my mind and will help great on my purchasing! Our condo does have a HVAC systems in each unit, but that is for the house's cooling and heating, I guess turn on the fun would help? Or the HAVC you've mentioned is something related to the cooking system. I knew I'm a dummy in home improvement... :)

You ;may want to read the many hood threads here to gain a broader appreciation of the entire topic. For perspective from a commercial point of view, the Greenheck guide at: http://www.greenheck.com/media/pdf/otherinfo/KVSApplDesign_catalog.pdfhas a lot of relevant information, particularly in the first dozen pages or so.

Make-up air (MUA) is the air supplied to the hood from somewhere else, ultimately from the outdoors. It replaces the air exhausted by the hood to the outdoors. The easiest scheme, if not a violation of some code, is to open a window. Note that even a window screen will have some pressure loss, and in cold environments, this approach has its deficiencies.

Other schemes are large ducts with spring loaded or motor controlled dampers, filtered versions of these which may need blowers to make up for the pressure loss, and even heated air approaches. Costs involved can equal that of the hood, or even the hood plus stove.

In a simple view, MUA deficiency just gags the hood blower. But there is also a safety aspect. If the residence contains any combustion appliances, such as a gas hot water heater, furnace, or dryer, low interior pressure from running the hood with insufficient MUA may cause back-drafting of the appliance, and addition of carbon monoxide into the living spaces.

Generally, residential HVAC does not have the flow rate needed for cooking ventilation MUA purposes, but this is something you may need to check with a qualified person.

Kas,

Thanks again. Do you know the Zephyr Hood? Are they effective and lasting long if the spec match up the requirements?

I don't own a Zephyr so I can't comment on it. Search this forum for any Zephyr comments others have made. There are probably different models of Zephyrs, so that needs to be kept in mind.

Generally, hood specifications are not lies. (Exception: Vent-a-Hood Magic Lung hoods do not use magic). However, most hood specifications do not address the issue of actual flow rate in the environment that they are integrated into. Hence, my attempts to recommend what the rated blower flow rates should be to get actual flow rates that will achieve desired performance.

If possible, audit hoods at your friendly appliance shop so you can hear how loud they are. In your case, you have no control over where the blower can be and you cannot include a silencer in the ducting, so you will have to bear with the hood blower being mounted in the hood not far from your ears.