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Old 02-07-2010, 11:49 AM   #31
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Chimney Drafting Seems Un-Solveable


Blower door test was not done right. or they chimney would have shown right away.

The chimney can be at the right height to the roof line that the wind changing direction slightly can influence the draft as an up or down draft.

Get a real chimney guy to check it out.

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Old 02-07-2010, 11:52 AM   #32
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Chimney Drafting Seems Un-Solveable


I got the impression from the post about the air intake that it wasn't 100%. Maybe I'm mistaken.

Something in that basement is creating a vacuum, just need to figure out what it is, and seal it or provide outside air intake for it.

Wait a minute. The flue damper on the oil furnace. It's drawing from the basement air. That can create a huge vacuum, especially for such a high chimney.

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Old 02-07-2010, 11:52 AM   #33
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Chimney Drafting Seems Un-Solveable


Beenthere: Yep. I have seen chimneys change/lose draft just from changes in outdoor temp vs indoor temp (delta T) and changes in barometric pressure. Sure am glad we got away from natural draft furnaces. Power vented is SO much better.
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Old 02-07-2010, 01:21 PM   #34
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Chimney Drafting Seems Un-Solveable


would an air radan system matter? I know it creates a vacuum, but I can't imagine that is what would be causing this.

Also, in regards to the vacuum, why would there still be one when I turned the boiler off? Wouldn't that reduce/eliminate it?

I will try and find a chimney expert, but my experience thus far is they know about dimensions, but do not know why/if it creates the negative pressure or drafting. Does anyone know what that person would be called?
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Old 02-07-2010, 01:27 PM   #35
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Chimney Drafting Seems Un-Solveable


There are companies who professionally do air balancing in commercial bldgs. Huge negative pressure problems with exhaust fans in restaurants/laundromats/high rise bldgs. Maybe they can help you. A house is like a living being. Hot air naturally rises in multiple story homes and creates convection currents/drafts/vacuums. Heat also flows from hot to cold and creates convection currents along large colder glass windows and walls. These are some of the reasons you are getting airflow in your house. Blowing smoke or something visual might help. I had a large expensive over 2000 sq ft home in a ritzy part of my city with a 6" combustion air pipe right next to the furnace. Still had lots of downdraft from its chimney. Chimney was not extended far enough over the roofline which had several different slopes/elevations which create air pockets etc. Chimney met code but still did not work well. Guy went with a high efficiency furnace instead.
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Last edited by yuri; 02-07-2010 at 01:31 PM.
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Old 02-07-2010, 01:57 PM   #36
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Chimney Drafting Seems Un-Solveable


Radon control systems do create a vacuum. But it should not be enough to cause the chimney to downdraft.

You should be able to do the measurements of this yourself, if it is in fact a simple physical problem. This just requires systematic measurement. Must be done when there is no wind, since that can create house vacuums just from convection through the house.

1. Turn off the boiler, seal the flue damper, and turn off the radon control system (no, a few hours of whatever radon is being generated will not hurt you, unless your home is on top of a uranium waste pile). Close all windows and doors.

2. Open a basement window an inch or two. If there is a big gust into the basement, then you have some sort of air channel that is creating a vacuum, and you'll need to figure out what it is. If not, turn on the radon control system, see if the amount of air blowing in has changed dramatically. Very unlikely, in my opinion.

3. Now open flue damper and turn on the boiler. See if the situation changes.

4. Do a similar measurement on each floor of the house, to determine where a vacuum might be generated.

If the situation seems to change with outside wind, you may just need a vacustack on the chimney.
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Old 02-07-2010, 05:59 PM   #37
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Chimney Drafting Seems Un-Solveable


Quote:
I will try and find a chimney expert, but my experience thus far is they know about dimensions, but do not know why/if it creates the negative pressure or drafting. Does anyone know what that person would be called?
The ones that just talk about chimney dimensions, are usually just masons turned sweeps.
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Old 02-07-2010, 06:57 PM   #38
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Chimney Drafting Seems Un-Solveable


How do I seal the boiler's flue?

Also, do you think that will matter much? I pretty much did everything you suggested, except I did not close the flue of the boiler and when I opened the window it was gusts of air being sucked in.
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Old 02-07-2010, 07:03 PM   #39
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Quote:
Originally Posted by dwk02020 View Post
How do I seal the boiler's flue?

Also, do you think that will matter much? I pretty much did everything you suggested, except I did not close the flue of the boiler and when I opened the window it was gusts of air being sucked in.

With boiler power turned off. Just wrap plastic around it.

Was teh boiler room door open when you opened the window.
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Old 02-07-2010, 08:34 PM   #40
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One other question: where are the Hydro Air systems located and how are they ducted? That is, where do they get their intake air, and are there return ducts back that are the same size as the primary ducts?

If these are unbalanced, then that might explain part of the problem. If there is a vacuum in the basement, and it is not caused by the boiler or flue, and one of the Hydro Air systems is down there, that implies that this system may be causing a vacuum, pulling air from the basement where there isn't sufficient return, and maybe from the first floor as well, especially if the basement door isn't sealed well. If one of them is going to the second or third floor, for instance, where there might be an open window, or a lot of room-to-outside leakage, then your house becomes a giant air duct, sucking air from the basement and first floor and leaking it out on the upper floors. The "defective" chimney is supplying some that air, thus making the entire house smell of charcoal.

This is just a hypothesis, but it's the only thing that makes any sense to me.

By the way, this IS very important to solve. The smoky air is not good for you, contains lots of nasty partial combustion chemicals (benzopyrene being the worst, same as smoking cigarettes).

Thanks
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Old 02-08-2010, 06:44 AM   #41
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Chimney Drafting Seems Un-Solveable


The boiler room door was closed and sealed with plastic when I did the test.

Jonathan -
1 air handler in the basement, 1 in the attic.
There is a return in virtually every room and the return is a 8" x 15" grate. Some rooms only have one vent, others have multiple. From the boiler room, it looks to me that the return ducts are the same size as the other ducts. The basement air handler has the plus air unit attached to it, so it is getting air from the outside as well as air from the returns.
The attic air handler, which supplies to the second floor and attic is the only place in the house that is not finished. The room where it is is an unfinished attic room and thus is much colder and certainly not as tight as the rest of the house.
Regarding your theory, it sounds good, but when I did my test and turned off the boiler and the air handler I still had the same problem where the chimney would draft into the house. So that makes me wonder if it is the problem you are referring to.
Regarding the chemicals - I am desperately trying to fix this b/c I know what your are talking about. We haven't had a fire for over a year so there is no more smell, but it still concerns me. As soon as I can figure out how to fix it, I'm going to.
Thanks for your thoughts all.
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Old 02-08-2010, 08:34 AM   #42
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Chimney Drafting Seems Un-Solveable


(I attempted to reply earlier, and the forum software had timed me out, and when I logged in, it hung).

I guess I have more questions:

1. I assume the house is open, with open stairwell?
2. Are the windows upstairs well sealed?
3. Is the attic access well sealed?
4. Are you sure that the entirety of the air intake for the furnace is outside air?

It also occurred to me that you might take advantage of the situation rather than fighting it. Assuming the vacuum isn't caused by some appliance or duct sucking air out, this might be the result of a multi-story home and natural convection. In that case, consider figuring out how much air it takes to solve the problem, and purposely have a duct bring in that much fresh air and heat it.

A typical 2000 sq ft home X 7 ft high ceilings, or 14,000 cubic ft, requires 4 air exchanges per hour for healthy living (Indoor Air Quality standards), to prevent buildup of outgassing from construction products and household cleaners. That's 56,000 cubic feet per hour, or about 1000 cubic feet per minute.

Badly sealed homes (typical) accomplish this passively, through cracks. Well sealed homes don't, leading to toxic building syndrome. I'm not kidding. Allergies, asthma, chronic fatigue, just awful consequences.

There's probably not much chance that that much is being pulled in to alleviate your vacuum problem. So it would be a good investment for healthier air in your house.

Meanwhile, let's figure out if we can solve this more easily...

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Old 02-08-2010, 08:56 AM   #43
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Chimney Drafting Seems Un-Solveable


5. Are there kitchen or bathroom vents to the outside?

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Old 02-08-2010, 06:26 PM   #44
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Chimney Drafting Seems Un-Solveable


You say any door you close sucks air. If it is sucking air it has to be going somewere. Go in the room with something that smokes or get a smoke puffer and trace the exhaust at least in the one room. You need to find were it is going. Since all the rooms do it and if they all tie to the same duct system I suspect it may be duct leaks or something in that system. It dosnt take but 5 min to do. Just pick one of the rooms in a negitave.
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Old 02-08-2010, 06:29 PM   #45
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1. The house is open - center hall colonial with open stairwell to 2nd floor
2. The windows are the same on all floors. The windows are Anderson model number CIG - 12-007. I think they are pretty good. When I put my hands around the frame I really don't feel cold air rushing in. On very cold days, I do get some condensation build up on the inside of the windows (the living side)
3. The attic is well sealed. Most of the attic is finished. The unfinished part has the air handler and is not that well insulated. The door connecting the unfinished and finished part is weatherstriped. The finished part is carpeted and I have something to block the air flow (not air tight though) from the bottom of the door to the floor. When I did my test, and it is still this way, I sealed the door to the attic. I taped off where the door meets the frame and then put plastic around the bottom of the door. It's about as air tight as it is going to get and I have left it that way.
4. I am not sure the entirety of my air take is from outside. How would I measure that?
a) Here is what I have that introduces air:
Plus Air unit - has a vent to the outside, which connects the air handler to the outside duct with insulated duct work. The idea is that it will pull the air it needs and introduce fresh air into our system. I know it is pulling air in b/c if I put my hand on the vent outside I feel it pulling.
Open air vent to the boiler room - just installed a 6" pipe that is connected to outside and vents pretty close to the boiler.
5) yes there are kitchen and bathroom and dryer vents to the outside. The kitchen vent is in a flat cooktop in our island, which has a vent that goes down into the cabinet and then out under the floor to the outside. Before, I got the open air vent to the boiler room this vent would stream in cold air as well. Since we put that in, the air drafting into the house is far less and maybe gone completely from this kitchen vent. So this further signifies that it may not just be a chimney problem, but that the chimney is one of the easier places to get the air from.

I think it is a vacuum problem, but I can't figure it out. If I open a window 4-6" the chimney drafts correctly, but I don't know why whatever needs that amount of air is not getting it. I would think the open air duct and the plus air would be plenty big enough to allow what is needed. If I made the 6" open air duct, like 12" do you think it would actually pull more air?

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