There are some youtube videos by Vent-a-Hood that talk about ducting, as well as many other sites. Mine is short so the in-hood blower is fine.

Basically, what my research found is:

1. Moving air makes noise, so the larger the duct the quieter it is.

2. Having the blower on the outside can reduce the noise--sometimes. This appears to be an "it depends" issue because if the distance the ducting travels is short, the location of the blower is less important.

3. Every bend you have in the ductwork restricts airflow. To get around this use larger ducting.

4. If you use flexible ducting, it needs to be even larger as the creases in the ducting restrict airflow.

5. Shorter is better for airflow.

6. The hood should overlap the cooktop by three inches or more on each side.

7. Don't forget about makeup air.

Search on "hoods" in this forum, read the resulting threads, and you
will find out more about the issues than you may want to know. Rather
than I expend from scratch the many column feet that the subject
requires, it would help if you reviewed several of the threads and then
narrowed the scope your questions. You might start with the FAQ at
http://ths.gardenweb.com/discussions/2766920/overview-of-vent-hoods

for a very generic overview (some of which might be contentious).

You
can search for kaseki + hood if you wish, but my oar has been dipped in
most recent hood threads so this may not narrow the field much. Maybe
adding "bluestar" to the search list will provide information on what
others have done. My commentaries tend to be about the ventilation
requirements and how to meet them, rather than what brand to select.
kas

Some immediate comments on Jerry Jorgenson's list.

Ducting has to be steel sheetmetal, and not flexible corrugated aluminum. The steel sheet metal is, nonetheless, somewhat flexible in handling, but not axially for bends.

Ducting diameter should be such that for the full power airflow, the velocity in the duct falls into the 1000 to 2000 ft/min range. This is to minimize grease deposition.

Pressure loss due to flow across the baffles will dominate pressure loss in duct transit.

kas

And one other point that may be of value: If the ceiling of the laundry room is high enough, then a silencer might be fitted to the duct. Used with an external blower, a silencer will greatly reduce noise, if that is a consideration.

Post your proposed kitchen floor plan in the Kitchen forum. I already see a problem with it and I'm no expert. Be sure to label all openings and adjacent rooms. They do a great job in the Kitchen Forum and can help you with ventilation, too.

Thank you for such quick replies. Kaseki I've read many of your informative and detailed comments on ventilation and have passed them along to DH.

The ceiling in the kitchen and laundry room are both 9 feet. The kitchen is only 18 x 13 and is open to the family room. This is an over 55 community and while there is no issue with installing an external vent for the ventilation we have to request permission from the HOA for an external blower motor. We're doubtful that they will approve it since the homes are close together.

Homechef - I certainly will post the layout on the Kitchens Forum when it's further along. This was just a preliminary. There will be an island instead of a peninsula. The clearance between the island (without an overhang for seating) and perimeter cabinets isn't as great as most designers would like but since it's just the 2 of us it will suffice. We're waiting to find out if the door from the kitchen to the laundry room can be moved to the right. There is an utility closet on the other side with mechanicals but even if we only gained a few inches it would be beneficial. However I would appreciate your thoughts on potential problems.

This is going to be a major transition for us. We've lived in our home for 33 years and have remodeled and improved it several times. My current kitchen is a wonderful 30 x 22 and it was perfect when we had 6 living here. But the time has come to downsize and since we're giving up our dream kitchen we've decided to splurge on this next one. We're gutting the kitchen, removing a half wall and buying new cabinets and appliances.

Here are 2 photos of the existing kitchen. In the second photo you can see the range on the outside wall where we want to put the dishwasher --- and the DW is where we'd like to place the range.

The contractor should know about moving the door to the laundry room when we meet on Monday. He has an architect going tomorrow to check out several details.

"The ceiling in the kitchen and laundry room are both 9 feet. The kitchen
is only 18 x 13 and is open to the family room. This is an over 55
community and while there is no issue with installing an external vent
for the ventilation we have to request permission from the HOA for an
external blower motor. We're doubtful that they will approve it since
the homes are close together."

This opens up three possibilities. First, conforming to the letter if not the intent of the HOA regulations, one could use an in-line blower after the silencer and before exiting the laundry room.

Second, one could be well-mannered and use a silencer on each side of the in-line blower if duct length is sufficient (or can be made sufficient).

Third, rotating the duct path near the end upwards through the laundry room roof may also be feasible.

You would likely be using 8-inch duct, I imagine, without our analyzing all the details, and the following is a link to the 8-inch size silencer. Note the dimension tab.
http://www.fantech.net/products/fans--accessories/accessories-ventilation/silencers/ld/ld-8-silencer/

kas

Kaseki - thank you for your additional comments. Our first choice would be to vent through the roof if at all possible. The small window that is furthest away is in the laundry room. The small window that's closest to the double windows is over the kitchen sink. The little vent next to it is for the existing over the range microwave exhaust.

One possible drawback is that the neighbor whose home is out of sight on the left is a HOA member and we feel we need to be a little cautious in our requests. And if the external components on the roof are visible from the street (and we think they would be) then it definitely will be denied.

Our second choice is venting through the laundry room. The contractor would run the ductwork above these cabinets which back onto the kitchen wall.
Thanks again for your suggestions. We'll add them to our discussion list when we meet with the contractor next week.

Maire

jpon - Thank you for taking the time to register to offer your insight. I am envious of your 48" Bluestar. We'd love to have a 36" but as you can see from the photos we just won't have the room.

It's very encouraging to read about the reduced sound level of your set-up and nd definitely something for our contractor to consider. I'm hoping he's already done his homework on this issue and comes prepared with ideas.

It's good to know that the baffles are easy to clean and fit in your dishwasher. We're really looking forward to trying out the higher BTU's . I've never had a hood. In our house our Dacor 6 burner rangetop is on an island with a pop-up vent which somewhat restricted our cooking.

DH and I are also retired and it seems we have the same concerns you did. I'm so glad you posted about your experience. How interesting that you can roast your beans indoors. And thank you too for your good wishes.

Maire

Is that a heat pump near the laundry? It might be useful to take a measurement of its loudness when at full power to compare with an external hood blower.

Are you on a slab or have a basement?

Also, if a small chase can be built on the side of the house, the blower could be put low on the wall, hiding (from the street) behind the heat pump or whatever that is. Some shrub planting would not only hide it from the neighbor's yard, but would also attenuate the blower noise.

You could even use an inline blower in the laundry, duct its output out and down (or down and out), then carry the air flow below ground level to a back yard area where it could be diffused away. The in-line blower would be sized for the pressure drop it had to deal with -- probably not a lot more if the underground ducting was 10-inch PVC or even PE corrugated drainage pipe. Once outdoors and underground, fire resisting steel duct is overkill.

One issue, though, is that your laundry looks rather formal (for a laundry) and all this overhead ducting may need a soffit or other means of disguise. I'm not sure whether your window to ceiling space will allow a soffit sufficient to hold ducting, silencer, and potentially an in-line blower.

kaseki - thanks again for your comments - you are a wealth of ideas!

The largest rectangular unit on the side of the house toward the front is the AC. The next one (that looked like a heat pump) is a garden hose reel.

We are on a slab.

As for the formal laundry room - those cabinets above the washer/dryer match the ones in the kitchen and the bathrooms. When we gut the kitchen and master bath I plan on utilizing the old cabinets to improving the storage in the laundry area. There is enough room next to the washer for the laundry tub - either a wall mount or we may use an old sink base and install a deep sink in it.

However - it there is sufficient space - I really like your idea to run the ductwork through the laundry room, down the inside and then out and mounting the blower low on the wall. That would probably add two more 90 degree angles to the run. But it would be the most inconspicuous and we could use shrubs to hide it and help reduce the noise. We would have to move the cabinets and W/D to allow for the duct but that's possible. I need to see how the dryer vents - I can see the dryer vent on the exterior wall behind the hose reel. That might be something that the HOA would be more willing to approve.

I have no problem with a soffit to hide the ductwork. We could even replace the cabinets over the W/D with the upper cabinets from the kitchen - they're taller and the duct work could run through them. That way they might be a little more accessible in case of servicing.

Thank you again. Maire

When the route is set and the desired CFM are set, we can pick a blower that should be able to achieve that CFM at the pressure loss that the duct path might induce.

But wait, there's more! You will need to determine your make-up air approach, which entails an exterior inlet and a kitchen or somewhere outlet. (Maybe dump into all house registers.) This too could be an HOA issue that needs early definition.

NJ requires make-up air for any ventilation system over 400 CFM. When we met with the contractor 2 weeks ago I mentioned it to him. I know from the completed kitchens on his web site that he has installed higher BTU ranges in his projects (6 and 8 burner Viking, Wolf, Capital).

MUA wasn't even on the books when we put in a Dacor 6 burner (all 15,000 BTU's) with a pop-up vent in an island about 11 years ago . But we did install a Fantech air exchanger in our basement just to help eliminate the damp smell. The motor is in DH's work shop in the basement, there's an exterior intake and there are 2 vents in the finished game room. Combined with a de-humidifier it has completely eliminated all of the damp, musty smell. And the fan is exceptionally quiet. I surmise a MUA system is somewhat similar.

At our next home the furnace is in a closet in the laundry room and there are vents above it and registers there and nearby in the kitchen. Who knew that ventilation could be so interesting!

Thank you. Maire

If this furnace is a combustion type, I would recommend that a furnace-scale MUA duct be installed into the laundry room, else imperfect MUA for the kitchen hood may still allow back-drafting of the combustion gasses (including the carbon monoxide). HVAC and oil supply companies can install these. I have one on my oil blown boiler.

The real issue is that the local Code requires MUA above a certain nominal hood flow rate, but doesn't address, much less test for, the underlying reason -- back-drafting CO into the house. The real safety requirement is to not cause the differential pressure between the furnace air intake at the furnace and the exhaust exit outside to fall below a certain value. For gas appliances this is about 0.03 inches of water column (7.5 pascals). Blown oil furnaces can stand more so long as there are no air leaks in the chimney masonry. (I've seen a list of pressures for this issue somewhere on the Internet, but don't recall the source.) Achieving this relatively minimal differential pressure in a house of unknown leakage, window state, bathroom fan state, fireplace usage, hood power setting, etc., not to mention a laundry room with a door to the kitchen that may be open or closed, with a furnace register that may be pushing air or not, is a rather hit and miss process without a complex control system for a powered MUA system.

This is why I recommend separate MUA for such combustion appliances wherever feasible, and let the MUA for the hood be good enough to (a) meet code, and (b) not restrict the achieved air flow through the hood. Mesh and baffle restrictions (possibly between 0.1 and 1 inches), along with other factors, should dominate the imperfect MUA pressure drop of a basic hood MUA, and hence the actual air flow should approximately meet the goal value determined from a desirable 90 ft/s air velocity over the hood entrance aperture area.

Having no carbon monoxide is always more important than having imperfect hood capture and containment.

I'd also put a CO sensor in that laundry room if the furnace is susceptible to back-drafting.

kas

Obviously this isn't my area of expertise but this discussion does make me wonder how knowledgeable the building code officer is when it comes to this topic. It seems that the code may be written to address a symptom but not necessarily the underlying cause. DH is safety conscious (perhaps a side effect of his profession) and he will insure that we have fire extinguishers, CO sensors and radon detectors in place. When the inspector visits the house prior to settlement we plan on having our HVAC contractor there also to check the gas furnace and AC.

Again - my sincere thanks. I'll print your posts for future reference. Maire