I just realized I posted an older version of this wall that specs the hood (which we had originally planned as wood) at 45" wide over 36" rangetop.

It is changed to 42" wide. Sorry for the confusion.

As retailer and distributor for ModernAire hoods on the east coast. Functionally it makes no difference at all. Visual wise 13" depth would be better. I would say that 90% of customers who have a 13" + top cabinet depth go with the extra depth. having said that to answer your actual question "its not needed".

Hi Trevor. Thank you for responding.

We are considering customization of the top of the hood.

This may seem like a silly question.

if we increase the top of the hood from 12" to 13 " depth to accommodate the 13" deep cabinets (without changing the depth of the rest of the hood), does that slight change in radius change the appearance of the hood?

Also Trevor is 1200 CFM correct for a 36" Wolf rangetop? Again, thank you.

If you go from 12" depth to 13" you wont notice the difference. I would always go with a 1200 cfm Blower.

Kaseki...thank you for the great explanation. It seems both you and Trevor agree with my kd and hood person that 1200 is correct. We live in the boonies so no one is checking on these things but I would like to get it right.

Trevor...so 1200 cfm it is.

I hate to beat a dead horse but may I ask two more questions?

-if I'm going to do a custom hood anyway, and I'm adjusting the length of the hood as well.....minimum above rangetop is 30" and maximum is 36" according to the Modernaire website. What height above rangetop do you think is ideal?

-is it a backdraft damper that keeps cold air from blowing back into the kitchen? Is that standard or something I need to make sure I am getting?

thank you for sharing your expertise.

I suggest that you draw to scale a side view of the range top and hood with a stick figure cook in front of the range. Observe sight lines to the pans at the back. Observe the effect of the (tallest) cook's bending forward on his head intersection with the hood. If the hood is drawn on a separate piece of paper, it can be moved up and down to see the effect of placement.

Mine is at 34.5 inches. While the hood should in principle grow in aperture area as the aperture is placed higher and higher over the range to maintain capture percentage, this is not usually bothered with in the region of 30 to 36 inches, particularly if you have already addressed hood overlap with the pan bases.

Note that commercial hoods typically are at seven feet from the floor, i.e., 4 ft above the cooktop. A typical size is 4 ft front to back and significantly longer than the cooking zone. This deals with the expanding rising plumes, and also with cross drafts, which should no be neglected from consideration in residential applications.

Forgot the damper question: "is it a backdraft damper that keeps cold air from blowing back into the kitchen?" Yes, that is its purpose, and I would recommend one at each end of the duct. Some hoods will include a damper. I don't know how standard it is to do so. Dampers and other duct components may be available from local HVAC distributors, or can be ordered from Fantech.

Thank you Kaseki for sharing all of your knowledge regarding both questions I asked here. DH is 6'2" and I am 5'6". So I am thinking it needs to go up. I will follow your advice and make sure it is at the right height.

i will also make sure that we have a backdraft damper at both ends.

thank you for the source fanteck

if my duct is round and 9 7/8 then I need a 10" like this one? Or two I should say. Thank you.

http://www.fantech.net/products/air-distribution-products/airflow-control-devices/backdraft-air-dampers/rsk/rsk-10-backdraft-damper/

Yes, that damper is typical. Note that neither side is shown crimped. Either one side has to be crimped (the one to be closest to the hood), or you need a band clamp such as Fantech sells for such purposes as attaching duct to their silencers.

Why the crimping?

Duct sections are typically crimped at one end so the section fits into another section. By crimping I do not mean mashing the entire end together, but effectively corrugating the sheet metal with the effect of making its diameter smaller. A typical do-it-yourself crimp tool:

Thanks Kasecki...found out the hood I'm using has a backdraft damper. Thought I would let you know since you have been so helpful.