WTF - sorry that is all I can say.

We did a semi-custom build too as in we bought a spec home under construction from a custom builder, but was able to make some changes and our Builder would have fixed that no questions asked if it was pointed out before he caught it.

Did you point out earlier in writing that the AC duct was going to be in the way?

"Are we overreacting or is this unacceptable?"

React away - that's a joke. Hope your agent is up to the task of seeing this redone properly.

Our agent is a firecracker, so I have no doubt in her ability to get the builder to fix this. The HVAC vent location was not noticed by me until after it was roughed in, although I don't feel like it should be my duty to be pointing such obvious stuff out to the construction manager. It was forwarded to the builder via e-mail, so the location mishap was documented. There have been numerous other "detail" things my wife and I have had to alert the CM about, which I won't elaborate on, but this one takes the cake. However, everything we have mentioned has been corrected to our satisfaction by going through our agent, so I can only hope this gets corrected as well. I showed our agent the pics this morning and she was fuming mad and also felt it was totally unacceptable. I haven't calculated the flow rate myself, but I can only imagine there is some huge efficiency loss due to the bends.

This post was edited by oksir83 on Wed, Apr 17, 13 at 15:22

I like the open space above the cabinets and think it would look bad to have a huge drywall box above the range hood cabinet while the other cabinets have open space above. I don't know anything about loss of efficiency in the air flow but I would have been livid if the builder had done what you are proposing. Just my $0.02.

While I respect the design you prefer, I have always personally seen the ducts run straight up and enclosed w/ dry-wall and trim, never run through a back wall into an adjacent room. Regardless of anyone's preference, I firmly believe the builder should have consulted with us instead of just choosing A vs. B. We have made them aware time and time again that we will be happy to come on site if they have a question or take calls/e-mails, but they refuse to consult us on various issues and usually end up going back and re-doing it to our satisfaction. One would think they would eventually learn to involve the homebuyer...

They never want to involve the homebuyers to much to keep the job from bogging down. Yes, the angle of that line needs to be changed in I'm opinion who's paying for it is another question.

What were they thinking? Maybe "I can't see it from MY house."

What diameter is that duct?

Each 90 is about equivalent to 10 feet of straight pipe, maybe a bit more (I have a spreadsheet somewhere to calculate pressure drops). If you have fan curves for that hood blower, you could estimate the actual flow you will get.

8" ducting. VAH docs say each 90 is a 5' straight duct equivalent, but every 10' over a 20' runs needs to size up 1" in the duct diameter. I measured and the current total run is right at or a hair over 30'.

This post was edited by oksir83 on Thu, Apr 18, 13 at 9:42

That looks positively peachy compared to this installation by a jerk of all trades whose work I inherited.

Worthy-- I know that guy-- he used to be my landlord!

oksir83,

Do you mean that it is presently 30' including allowance for the two 90's and the 45? If so, you should get about 500 CFM, which is not terrible compared to a spec of 600 with no duct at all.

I hadn't realized at first that you didn't have cabinets all the way to the ceiling, as I do. I can see why they made the choice they did. My contractor is the same -- always going ahead when he knows he should be asking me first; it has cost him a lot of time and money having to fix things he thought he was done with, and I have a lot of details that I don't like now.

I went back and re-measured and the total length allowing for all the bends is the equivalent of ~40' right now. In reality, they would need to increase the duct to 10" to not have the efficiency drop per the VAH specs.

My wife said she might be ok if the duct were run to the left and into the top, back corner of our Master closet, because in her mind it wouldn't be so visible. Right now, the top corner of the laundry room is just so "in her face" as she likes to put it. In reality they had 3 directions they could run it and chose the last one we would have chosen.

FWIW, we have a meeting with the actual builder/owner, company CM and neighborhood CM, along with our agent in the morning. I'm hoping it turns out well.

If you put it through that closet, see if you can make two of those 90's into two 45's, as an offset.

I dont think they did much wrong other than not involving you on a possibly emotional kitchen design question. With the hundreds of decisions that builders and owners should collaborate on, its tough for builders to find the right balance to keep things moving in the field. A differed decision on the issue might have meant an extra trip charge from the sub.

I bet a bigger problem is that you have no source of make up air. This is required by most codes for kitchen vent hoods over 400CFM.

Better airflow for you kitchen vent hood means more risk of backdrafting combustion appliances, sucking in CO from the garage, pulling more radon into the home and introducing more humid air into the leaky building cavities which can contribute to mold and mildew growth.

The MUA is not my problem. We spec'd the hood before signing our contract and IMHO, it is their responsibility to make sure installation meets and passes code, which I am not familiar with.

Well even if its not required by local code, it probably will be soon because it is currently required by international building codes.

It is your problem because it is your indoor air quality.

Its ok, youre not alone. Most builders, designers, and architects havent a clue about this important issue.

I have conflicting info of whether or not it is required at 400 or 600cfm. I am not even sure it is mentioned in our local codes and I don't foresee there being a time I would ever have the hood full blast, let alone with every exhaust fan running in the house. I guess the real issue could be at re-sale if it is implemented. If that is the case, I would likely just remove one of the blowers making it a 300cfm unit if the time came to pass an inspection. We are having a well-respected 3rd party inspector do the final inspection (in addition to what the city does), so we will definitely know something then.

I have conflicting info of whether or not it is required at 400 or 600cfm. I am not even sure it is mentioned in our local codes

Do you fall under the 2009 International Residential Code? If so, here is the relevant section:

M1503.4 Makeup air required. Exhaust hood systems capable of exhausting in excess of 400 cubic feet per minute (0.19 m3/s) shall be provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system.

Of course it is also possible your area does not enforce that section of the IRC.

The problem with removing one of the blowers is that normally code requires the hood to be the size called for in your range specifications. Therefore, it is possible a 300cfm unit will not meet code.

oksir83,

Where are you located?

Here in San Jose, CA, the MUA requirement doesn't apply if there is nothing in the heated envelope that can be back-drafted (gravity appliances such as gas tank water heater, gas furnace, maybe fireplace). Even then, only if the largest two fans (maybe hood and either clothes dryer or bathroom fan) exceed 15CFM per 100sq ft of house. e.g., for 3600 sq feet, I could have 540CFM, even with a gas water heater inside. I moved mine to a closet which is sealed from the inside, vented to the outside, so that I could safely go a bit higher.