Venting your hood into the attic is dangerous and illegal - codes do change but this situation was never ok. It's not clear to me why the carpenters were installing the duct in the first place - that's not normally a carpenters job. In any case, it's good that your GC caught the problem. It's your choice now whether to have it go through the roof or the side of the house but don't have the carpenters do it.

Thank you, Weissman. Having never done this before, pardon my ignorance, but which tradesman are supposed to do venting installations? HVAC guys?

Also, just how dangerous is this situation? That didn't occur to me as they said that the duct was very close to the existing vent, so everything was going outside anyway.

I was able to speak with my husband and he OK'd the venting through the wall, so that was done yesterday. Should I hire an inspector to make sure it was done correctly?

Luckily we haven't made the final payment, so I feel we have recourse about this, especially since the contract specified installation and venting and they are not completing the work.

Venting is done by HVAC. Venting into the attic can cause a fire, mold (due to moisture), grease build-up and, in cold climates, ice dams through heating the roof. It has been illegal to vent into the attic for kitchens or bathrooms since, basically, dirt. This is astonishing ignorance of the law on your builder's part.

You don't have to "hire" an inspector. Did you pull a permit? If so, the plumbing inspector should view your vent installation before he signs off on your project.

I'm getting a bit mixed up. When you say 'chimney', do you mean the pipe from a fireplace?

If I understand you correctly, you are saying that they ran the vent pipe for the range hood over to an existing 'hole' with a cap/cover being used by something else (I'm guessing a bathroom vent). They then terminated the pipe at this cap/cover along side the existing pipe. If this is true, this is how my two bathroom vents are installed. That is, both vent pipes (about 4" each) terminate to a cap/cover on the roof that is about 8" in diameter. I'm assuming this was fine when the house was built. It may also be 'code' now in my area, I don't know.

But I've never seen this done with a kitchen range vent. I would think they would have to be separate since their airflow rates are higher.

Codes do change. It would be nice if the contractors would keep up with these changes but it does not surprise me that they would not. They will find out at inspection time.

Given a choice between going straight up through the roof or 90* through a wall, I would go straight up. The 90* turn adds an effective 15' to the vent pipe.

I think what W is referring to is if the vent pipe stayed in the attic and never approached the outside, that the range hood would vent all the smoke/junk directly into the attic and not outside at all. This would not be good.

Hmmm... much appreciated, Marcolo and weedmeister, now:

Marcolo... The contractor did get permits and an inspector came out and signed off on it about a month ago. He did not go into the attic or onto the roof to confirm that the venting went through the wall or through the roof. He did go outside and therefore must have seen the existing attic vent. I remember mentioning that I hoped the venting was to the outside cause I hadn't seen anybody on the roof. At the time, he didn't show any indication of concern about it. So, I thought it was safe to believe everything was correct. I am a worrier by nature so it's hard sometimes to be confident that my worrying is called for. Could it be that now, a month later, the inspector called the contractor about it and that's why they disclosed the error? I assumed they told me cause they had to come clean since the the new installer would see it and most likely tell me.

weedmeister... By chimney I meant decorative stainless steel casing above the range hood that covers the range hood motor and ducting and goes straight up an inch or two above the drywall. There is no existing vent or pipe cause we moved the cooktop off of an island and onto a perimeter counter so that we could have an updraft vent. (Didn't want another downdraft cooktop cause I was afraid that like the previous one, it just wouldn't ventilate well enough). Also, the contractor said venting through the wall was a better option because venting through the roof would ultimately lead to leaking problems. In hindsight, I guess leakage from a vent in the roof shouldn't be a concern if it were installed properly, by a qualified person.

It will matter whether it's a steel or shingled roof. NOTHING should pop out of a steel roof (at least in snow climates) near the eaves. Snow can get a running start and tear it off. I just had a customer who got a call from one of his customers saying that three skylights were in the driveway when a glacier let loose.
About codes... Up here in Maine, we've just adopted the national building codes this year, and they are pretty radically different than what everyone is used to. If your state has done the same recently, expect confusion. Most of the contractors up here are like deer in headlights.

Our old range vent used to exhaust into the attic. We had a persistent problem with peeling paint on the kitchen ceiling. You don't want this problem in a cold climate. Vent to the outside, even if it's not in code.
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You probably didn't hear my renovation sob story dealing with the placement of a range and hood based on an assumption made by our addition's designer. He must not have known that it's against local code to vent into a walkpath (sidewalk alongside addition) so he laid out the infrastructure of the room so that the vent would NOT go up and out the roof. Once I learned that during our first onsite inspection the city inspector vetoed his vent plan and required us to do a plan B that went straight up and penetrated the roof near the peak, I went ballistic and sulked for a month. (A design using a roof vent that I had argued in favor of had been laughed off by DH and the designer who both thought the designer had the better design. One of the low moments in our planning phase.) Upshot is that we now have a very very tall vent up to the roof near the peak and seen by the street (all the things that were considered inefficient and unsightly and a joke a year ago). However, we do have a good kitchen now, but I wouldn't recommend this process to get there and we're still worrying about the implications of deep snow pack by a warm moist vent in future, so DH will need to scrape snow off roof by vent for the rest of his life in this house. ["Get over it, Florantha! Stuff happens."]

Thanks, Florantha! We most certainly do want it to vent to the outside for that reason and because it is the code. I am so, so disappointed in our contractor and carpenter for trying to cut corners at our expense and lying about it.

I do not remember reading about your situation but now can truly relate. I hope scraping the snow by the vent hasn't been too bad for your DH although I know you've gotten a lot of snow up there this winter. :)

Why wasn't the GC instructing the carpenters on how to do it properly BEFORE this got installed?

Exactly, antss! But, unfortunately it appears that they knew they were cutting corners and only came clean because they had to.

Never assume that builders or architects know the building code, or if they do, follow the building code. We just went through a nightmare and hired a new GC to finish our large project. There were many building code violations ignored by the architect and builder -- and these were well-known people in their field.

Unfortunately it is all too common for contractors to tell you everything is done according to code when you confront them -- what else are they going to say? This is a shame because it gives the other quality contractors out there a bad name.

No time for the full story now, but I suggest you Google your local building code and the issue you are faced with to get the code information, and/or call the local permitting department with your question. I would call the local permitting department only as a last resort if you cannot get the information yourself. Listen to the what the workers with "boots on the ground" tell you about your builder.

Billy

Here's an example of a relevant building code. You need to to determine the code for your location, as they may have adopted a later version of this code or modified it.

Google is your friend.

Billy

COPIED SECTION INTERNATIONAL RESIDENTIAL CODE 2003;

SECTION M1502
RANGE HOODS
M1502.1 General. Range hoods shall discharge to the out-
doors 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 in-
side the building.

Exception: Where installed in accordance with the
manufacturer�s installation instructions, andwheremechan-
ical or natural ventilation is otherwise provided, listed and
labeled ductless range hoods shall not be required to dis-
charge to the outdoors.

M1502.2 Duct material. Single-wall ducts serving range
hoods shall be constructed of galvanized steel, stainless steel or
copper

M1502.3 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 accor-
dance with Section M1506.3.

M1506.3 Ventilation rate. Ventilation systems shall be de-
signed to have the capacity to exhaust the minimum air flow
rate determined in accordance with Table M1506.3.

TABLE M1506.3
MINIMUM REQUIRED EXHAUST RATES FOR
ONE- AND TWO-FAMILY DWELLINGS
AREA TO BE VENTILATED VENTILATION RATES
Kitchens 100 cfm intermittent or 25 cfm continuous

Billy G,
How easy is it to hire a new contractor when you are in the middle of an agreement?

Thanks, Billy G. Thanks to your suggestion I was able to find out that our municipality adopted the International Residential Code in 2009, with full implementation by Nov, 2010. So, seems to me they have had plenty of time to revise their practices.

It's not clear to me if the carpenter who installed the duct has any kind of mechanical license. And, I was unable to find any kind of list of licensed carpenters to see if they at least had that. If the installation was done by an unlicensed tradesman, is this a problem for us?

I should probably also restate that the kitchen has already been inspected and signed off on by an inspector.

When you all say "vent into the attic', you are referring to venting stopping in the attic and blowing grease around your attic, right? I know this is very very wrong.

But maybe I am reading the rest of it wrong; I'm also hearing that it's not okay to vent up and out through the attic via an exhaust top thing. I have a hard time believing that that is not acceptable. Our range is on an internal wall and I see no other option other than through the roof. Someone made a point about exhaust caps being a problem on metal roofs, and I can absolutely picture the issue of sheets of ice ripping the caps off. However, what do those people do about bath and kitchen exhausts?? I could run the vent 30' laterally to the gables, but that doesn't seem very efficient. I thought I understood it all before and now I'm a bit confused!

@lithigin, it depends on where you live and your local code. Where we live (California), roof vents are fine (that's what both of ours are, and peering out at the four neighbors whose roofs I can see from this perch, all of them have roof caps too) but in some places that get heavy snow, the code says they must be through the wall so they aren't blocked and don't develop leaks if snow is piled on top.

@cfire, I'm curious to know what your vent situation actually looks like in the attic---have you taken a peek? Is it possible that some of this is just a miscommunication, and what the contractor meant is that they ran the vent up into the attic and tapped into the existing ductwork and roof cap, not realizing that the code said they needed to go through the wall rather than through the roof? (They shouldn't have done it that way either for a range hood, but it is something that used to be to code in some areas and might still be in a few places, and in many places you can still combine bathroom vents or other non-kitchen vents as long as the ducting is properly sized.)

@lithigin... It would be ok to vent through the roof and that is within our Residential Building Code. But, ours was never vented through the roof. The duct just ended inside the attic, near an existing attic vent to the outside.

@lithigin and @artemis78... Well, I did not get to take a look at it in the attic. And, I would like to believe that it was a miscommunication, but they told me they ran the new vent duct into the attic next to but separate from existing ductwork so that it ended behind the attic vent to the outside. They said they also fastened a screen over the end of the duct. So, the unfortunate truth is that the cooktop vent ductwork was simply never truly vented to code. Whether or not it was vented to the outside, I guess, is in the semantics. The contractor and carpenter stand by their original work insisting that having the duct near the attic vent is appropriate as the attic vent goes to the outside. The dishonest part is that they led us to believe the cooktop duct had been vented to the outside TO CODE, when they knew it wasn't, even after my questioning them about it on several occasions.

We did end up allowing them to correct the situation the way they suggested, through the outside wall. (At the time, I had asked them if a roof vent would be better, but they said it wasn't due to possible leak problems and my husband agreed with that.) So, now there is a separate grill vent directly below the existing attic vent. It works (the flaps lift up when the vent is turned on) and isn't particularly obvious or ugly from the street.

I suppose once the new custom decorative chimney is up on the cooktop wall this won't seem nearly as bad as it does right now. (I have already found a fabricator and someone else to put it up --a recommendation from my real estate agent friend.) It's just that my trust was violated and it stings a lot right now.

Instead of sitting around feeling sorry for myself, I am going to have to spend some time learning how to post pics (thank goodness for the instructions!) so everyone can see the finished results. Thank you for taking time to respond to my post.

My 740 cfm vent hood fan cannot hold up a napkin. Nothing seems to vent.
What is an easy to tell if the builder's installation meets IRC code of 25 cfm?

Oh boy... that's a tough one. I think the easiest way would be to call your county's residential building inspectors and ask for one to be sent out to look at it.

In our case, an inspector had already signed off, so I assumed everything was OK. When I called the inspector's office after the fact, I was told that checking the vent (other than turning it on) isn't on the inspectors' checklist, so an inspector wouldn't look unless he had a specific reason to.

I hope this helps a bit. Or perhaps another member with more HVAC know-how might have some better ideas for you.

Good luck!