microwave exhaust vent

[Barry Adair]

if we're talking combo micro/range hood vent get the make and model off your unit and follow mfr recommendations and code

SECTION M1503
RANGE HOODS
M1503.1 General. Range hoods shall discharge to the outdoors
through a single-wall duct. The duct serving the hood
shall have a smooth interior surface, shall be air tight and shall
be equipped with a backdraft damper. Ducts serving range
hoods shall not terminate in an attic or crawl space or areas
inside the building.
Exception: Where installed in accordance with the manufacturer's
installation instructions, and where mechanical or
natural ventilation is otherwise provided, listed and labeled
ductless range hoods shall not be required to discharge to
the outdoors.
M1503.2 Duct material. Single-wall ducts serving range
hoods shall be constructed of galvanized steel, stainless steel or
copper.
Exception: Ducts for domestic kitchen cooking appliances
equipped with down-draft exhaust systems shall be permitted
to be constructed of schedule 40 PVC pipe provided that
the installation complies with all of the following:
1. The duct shall be installed under a concrete slab
poured on grade; and
2. The underfloor trench in which the duct is installed
shall be completely backfilled with sand or gravel; and
3. The PVC duct shall extend not more than 1 inch (25
mm) above the indoor concrete floor surface; and
4. The PVC duct shall extend not more than 1 inch (25
mm) above grade outside of the building; and
5. The PVC ducts shall be solvent cemented.
M1503.3 Kitchen exhaust rates. Where domestic kitchen
cooking appliances are equipped with ducted range hoods or
down-draft exhaust systems, the fans shall be sized in accordance
with Section MI507.3.

[Stephen P. Shockley]

I dug up the owner's installation manual on line. It only says you can roof vent it or wall vent it, but doesn't provide any details of the venting after the connection to the unit.

[Bob Elliott]

Originally Posted by sshockley

Bob,

Would it make sense to angle out of the top of the microwave hood and go through the wall in the laundry room and then straight up through the roof of the one story laundry room/garage area? That would be a couple of quick elbows and then straight up.

I can hide pretty easily in that laundry room by hanging a couple of cabinets in there. Exactly how straight up does it have to be in the vertical section of pipe? I've never done any ventilation work except to repair some open seams in an HVAC duct.


Regards,

Steve

Rather than us trying to guess it all Stephen this link has exact requirements for installation on these hood models.
Check it out as it will help you.
http://www.thefactoryoutlet.com/kitchen/range-hoods/

Back in my install days we would just run flex to a side wall.Often we would ask the client to install cabinets to hide the vent run.
It is really pretty straight forward as there are no worry s about clearance like a furnace vent.

[Stephen P. Shockley]

Bob,

I think you're dead on about going to the side wall. In the long run, a soffit might be the easiest way to get it done. I'll check out the shortcut you posted as well.


Thanks,

Steve

[Bob Elliott]

Originally Posted by sshockley

Bob,

I think you're dead on about going to the side wall. In the long run, a soffit might be the easiest way to get it done. I'll check out the shortcut you posted as well.


Thanks,

Steve

Easy to do.
Just drill a series of holes with a masonry bit and then chisel it out with a sledge hammer.
Use urethane instead of silicone in my opinion as the silicone does not stay sealed well to the brick often.
Remember to chisel from the outside to avoid spall gaps or pop outs.

If you get any my trick was to use brick pieces and dust rubbed into silicone to blend it.
Extra cabinets are always nice.

[John Allingham]

Originally Posted by Brian A. MacNeish

Just about everyone I've seen are convertible, but you have to get the original or another OEM blocking piece for the front exhaust also.

The most common error I see with the vented hoods is the size of the recommended ducting (5,6,7" diameter or 3.25" X 10/12") is reduced to 4".......all most people can relate to is 4" dryer duct, I guess! The metal knock-out on the top or rear of the rangehoods/microwave exhauster is usually 3.25" X 10 or 12"- a standard pre-manufactured store shelf piece (know as "wall stack" by many for taking air upstairs in 2X4" walls). What I see is a "boot" (transition piece) of 3.25"X10" at the unit reducing to 4"!!! It starts with 32.5 sq in and ends up with 12.6 sq in........choked off......try and work well now you little........and all this is with a poor, bottom-of-the-barrel $40, no strength, propeller type range hood in the majority of cases. Start with crap, add more crap and wonder why it won't work well plus being noisy!!!

In Canada, we (since 1995) have had codes that require quiet fans (who'll turn and leave on a noisy fan?). All bathroom fans must be 2 sones or less and kitchen exhaust fans must be 3.5 sones or less. I go to the big box stores with their "wall of fans" you can try and find 90% or so don't meet the codes in effect........let the homeowner buy the cheap fan (that's all he's willing to pay for it anyways and a fan is a fan....we don't do that with our cars--a Yugo is not a Lexus but they are all cars) and put it in poorly.......we made our money......it's all we really care about! I just saw a $750 (cost of unit only) brushed stainless steel Italian range hood that you could only really use on low speed due to noise if you were working right beside it

Hi Brian
My copy of the Ontario Building Code (2006) says "no rating required" for kitchen fan sones.

[Brian A. MacNeish]

Originally Posted by jallingham

Hi Brian
My copy of the Ontario Building Code (2006) says "no rating required" for kitchen fan sones.

Yepp!! you're correct for your jurisdiction which re-issued its own OBC (generally based on the NBC) in 2006.

With the NBC, during the period from 1995 to 2005, they broke the 5 year "new code" release cycle due to the change in philosophy of trying to get performance or "objective" based intent into the code rather than it being totally prescriptive. While working through these changes and accompanying issues, there was no "new" NBC issued in 2000 as would have been customary.

In NS, the current edition of the NBC is usually adopted by the NS Building Code Act from 1.5 to 2.5 years after it is released (the 2010 NBC is to be made law here June 1, 2011). In the period that I wrote that post (2007) , the 1995 NBC was still in place here. Later in 2007, the 2005 NBC was adopted here also- the 3.5 sones or less for range hoods requirement disappeared.....the manufacturer's were complaining it was too stringent.....(read: we really can't make them as quiet as you want!!!)

The intent of having quiet fans is to have people use them.....they won't use or leave a really noisy fan "on" for long.....defeats the purpose of putting them in our newer, energy-efficient, airtight homes), doesn't it?

[Bob Elliott]

Brian ,the fans are built in to the units.

[Brian A. MacNeish]

Originally Posted by belliott

Brian ,the fans are built in to the units.

Bob......

HUH??? What are you trying to educate me about?

[Bob Elliott]

Originally Posted by Brian A. MacNeish

Bob......

HUH??? What are you trying to educate me about?

Never mind ,your last sentence sounded like you were warning people to pick a quit fan.

Trying? subtle -subliminal?(good one)