You can get a 600 CFM hood that will work with a 6" duct. You really want to get a hood that matches the ducting that you have. Unless you have a grill, 600 CFM should be more than enough.

Our total BTU's are 89,000. 6 burner- no grill. I thought that means I should install a hood with at least 900 CFM? Will 600 be sufficient? Most of my cooking is things like chicken cutlets, pan seared fish, roasted meats, and vegetables. It is very unlikely I will have 4 burners, let alone 6, going at once. I would like to try wok cooking, however. Thanks for the input. Jenn

The theorectical rule is to total up all the BTUs like you did but that's generally overkill - as you said you'll never have all the burners cranked up to maximum at once. There was an article posted here a few years ago about how range/hood manufacturers are overselling people on ventilation. 600 CFMS should be more than enough.

Not an expert, but in general, the larger duct and the shorter the duct, with the least bends, the better. It's not the range per se that determines how much ventilation you need, but how you cook, considering the power the range has. Just frying bacon can require some venting. Most folks don't much mind the heat an oven gives off, but rather the smoke-(grease), steam, and odors of cooking on the burners.

This is so subjective to how you cook, or how you might start cooking with your new range. Some folks can manage with a window cracked open. Others need the max ventilation. Grilling is obviously the max. But you can also grill on a pan.

Most folks don't run their fans on HIGH for most of their cooking. Only for certain tasks.

Remember that as you suck air out of your kitchen, it has to be replaced from somewhere else.

If you want to have a large ventilation system, I would determine how much work it would be to replace the ducting.

Of course you can use a reducer, I'm not familiar (knowledgeable) if it would increase noise beyond what a 6" duct would produce. I would also guess that 600 CFMS is more than enough, but that size would also work better with a 7, or 8, or 10" duct.

I had a similar problem, and could only have a 6" vent. I spoke with numerous people about this and they all strongly cautioned against reducing the vlume of air from 8 to 6 inches. It may seem like a small reduction, but when you look at total volume, the reduction is more than 40%, which will make the hood noisy, and I was warned that it would likely result in breakdowns.

You'll also find that a 600 cfm hood will be tough to find with a 6" vent size. we went with a prestige proline, which seem to be popular on this board. good luck!