Mechanical inspector failed an inspection because there was no gable vent in the attic for combustionable air.
There are soffit vents every eight foot and three turbine thermostatically controlled vents these would seem to be more than adequit to provide air. What am I missing to understand this decision?
This house is one of My builder buddies projects that fell into his lap because of a divorce and the bank has asked him to finish out the house and I have been correcting the framing part.
ANDYSZ2
I MAY DISAGREE WITH WHAT YOUR SAYING BUT I WILL DEFEND TO THE DEATH YOUR RIGHT TO SAY IT.
Replies
You seem to think that the inspector was demanding more venting from inside the attic to outside air. Is it possible he was actually asking for, typically, a set of ducts going from the room with the heating unit to the attic?
These ducts are to guarantee make up 'combustion air' for the unit to breath properly. This makes them run more efficiently and greatly reduces the chances of having carbon monoxide being pulled into the living space.
Typically these ducts are in pairs, equal size, and sized for the flue size of the heating unit/s with a minimum size. Check with a HVAC/ mechanical contractor on sizing. One stops, the ends being open but for some screen, just inches below the ceiling height. The other runs down to near the floor.
There is absolutely no reason to bring in conditioned air when the unit is in unconditioned space.
Re: "There is absolutely no reason to bring in conditioned air when the unit is in unconditioned space. "
At no point in my post do I mention any conditioned air moving anywhere. Attic to, or from, the space containing the heating unit. Where exactly does the conditioned air come in?
Have you been smoking those irregulars again?
"Is it possible he was actually asking for, typically, a set of ducts going from the room with the heating unit to the attic?"
I missunderstoond what you said. And I looked back at the orginal post and realized that he did not clearly indicate where the equipment was.
I assumed that it was in the attic (and he later indicated that it was).
I told him it wasn't clear but I assumed it was a mechanical closet of some description. See a lot that way round here.
Don't understand adding venting to an attic if it is adequately vented to begin with. Sounds odd to me.
I suspect BH was right when he speculated that the inspector was concerned about the power vents, although why he then approved adding gable vents is hard to understand.
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Andy:
It's not clear to me what the air is for. Is there a furnace in the attic, or is it on the floor below?
Al Mollitor, Sharon MA
Its for hot water heaters and furnaces all in the attic space all having access to soffit vents in an attic spaces that probably total 2000 sq. ft with no obstructions. I mean this has to be the most open areas I've ever seen for furnaces and h2o heaters.
ANDYSZ2I MAY DISAGREE WITH WHAT YOUR SAYING BUT I WILL DEFEND TO THE DEATH YOUR RIGHT TO SAY IT.
Combustionable air ???
You may have coined a new word here at Breaktime..............(-:
I wonder if the inspector figured the "turbine thermostatically controlled vents" would suck air out of the attic, and maybe there weren't enough square feet of soffit vents. Hard to say without seeing the house.
Is it possible to provide a direct air source to the unit? Like a PVC air suply or something like that? Seems like that would solve the problem more easily than putting in a gable vent.
Sounds like the venting is kinda messed up anyway - There won't be any vetilation in the attic during cold months if the electric vents won't kick on.
Avoid cliches like the plague.
I think the same convection principals will work thru the turbine vents when they're not turning by motor.The house is 7800 sq. ft with 2 stories of attics and 8"x 16" sooffit vents every 8' ft and I would guess there are at least 50 of them.
ANDYSZ2I MAY DISAGREE WITH WHAT YOUR SAYING BUT I WILL DEFEND TO THE DEATH YOUR RIGHT TO SAY IT.
He did recommend putting in a roof vent over every gas device on his second visit but I already had scaffolding setup (6 tiers) and the gable vent is being brought out today.I just don't understand how the soffit vent is not allowed as the air source since that is where the circulating air is going to enter the house anyway.
ANDYSZ2I MAY DISAGREE WITH WHAT YOUR SAYING BUT I WILL DEFEND TO THE DEATH YOUR RIGHT TO SAY IT.
What I was getting at was that there might not be enough soffit vents. If all the electric fans were on and there wasn't enough supply air, there could be a "suction" in the attic.
That might cause the furnace to malfunction? (I'm guessing)
Or he might be worried that the soffit vents could someday be covered over by someone adding insulation in the attic.
Or he could just be a jerk who goes by the book no matter what. Hard to say.I'd give my right arm to be ambidextrous
Sounds like a confused inspector, although BH might have hit it with the observation about the power(?) turbines.
For natural draft and 80+ furnaces and natural draft water heaters, the flue gases are supposed be at .01-.02 water column inches. That isn't much at all, and it is fairly easy for a power vent to overcome that amount of draft.
I've done testing in newer houses where a 2nd story bath fan has significantly affected the draft of a basement water heater. (rare, but it has happened.)
It's too late now, I guess, but perhaps the best solution in this case could have been installation of a skuttle vent or 2: http://www.skuttle.com/216.html (The 216 doesn't seem to be much more than a barametric damper - they are requiring them in all new homes in MI with combsution furnaces/boilers)
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Tool Donations Sought
I'm matching tool donors to a church mission to Haiti - we're shipping a bus converted to a medical facility in (now it looks like) April and can fill it with clothes, tools and all sorts of stuff needed in that poorest of all countries. A few hand tools or power tools can provide a livelihood for an otherwise destitute family. Please email me if you have tools to donate.
Thanks to Jeff and David and Jim and Rich and Steven and Mark and Jason and Shep and Jen and Mike and Joe and Bill and Ken for their offers!
Several donations have arrived! Thanks and God bless!
In unconfined open indoor spaces the code requries 50 cu ft/ 1k btu's.
http://www.codecheck.com/pg21_22mechanical.html#combustionair
There is a separate requirement that if the atic is used as a source for combustion air then 1 sq in of venting is needed for 4000 btu's.
It is hard to tell from this summary what the exact requirements are as as the first case is for "indoor" spaces and the 2nd is for using ducts to bring in combustion air from the atic.
You need to look at the rule code book(s) to see how they are worded.
I don't see too many gas fired appliances up here, ( actually I don't know of any)but I can see three powered exhaust fans being a potential problem.What if the gable vents get plugged?
The best thing to do would be to check the draft in the vents with the fans running.Any problem may not show up until the summer time when it is hot outside and the draft can be as little as -.005"