scenario: I have a 1929 Tudor that had a gas fireplace which has been blocked off at the living room. The original boiler vents thru a flue next to the fireplace Flue. The flues are not capped.
Problem: the plaster is bubbling in a white powdery texture off of the chimney on the inside of the rooms. It only appears to be happening on the second (top) floor.
I thought the flashing needed to be replaced and had it inspected but it is fine. The roofer told me that he believes it is caused by an ‘Automatic Vent Damper’ that was put on the flue just above the boiler. This was put on before we bought the house last year.
Any insight into this would be greatly appreciated.
Thanks
Replies
Sounds like efflorescence. Somehow the plaster is getting damp, but not sure why--maybe the furnace gases aren't getting out of the automatic damper? They would contain water vapor that is getting through the chimney and dampening the plaster. All just guesses. Someone else should be along soon to shed more light.
Just thought of something else--I'll bet the chimney isn't lined, right? (No tile liner, just brick?) If that's the case, you can do one of several things and someone else can direct you to the best way to go, but my initial reaction would be to insert a stainless steel pipe from the top and vent the furnace (boiler, whatever) into it.
I believe it is lined. I can see the clay sticking out of the top.
The original boiler? From 1929? Post some pics!
Your problem is very likely condensation of the water vapors in the flue gases before they get out of the chimney. The condensate is pretty corrosive and can deteriorate the flue liner and then soak into the brick and plaster wall causing efflorescence.
Has anything been done to the system which has reduced the amount of heat going into the chimney (higher efficiency boiler? Water heater vented elsewhere?)
(This may be a new problem or an old one that has been chewing away at the flue liner for years and has just eaten its way through)
Can you safely look down the flue from the roof? Is the clay tile all pitted and spalled at the top or within view of the top?
Is the flue blocked?
This is a potentially dangerous situation and should be checked out ASAP by a qualified HVAC tech.
"Automatic flue damper?"
Do you mean a barometric damper:
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Or a flue damper which stops the flow of flue gases when the boiler first lights off and is producing the highest level of carbon monoxide?
Is the flue damper controlled by a motor which opens the damper before light-off of the burner?
Get it checked out and let us know what the experts say.
"It is as hard for the good to suspect evil, as it is for the bad to suspect good."
-- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)
Bob
The damper is a foot or so above the boiler. The label says Ameri-Therm Automatic Vent Damper by American Metal Products Co. I was told there are metal fingers inside the contract and expand depending on the temp.
After you questioning the age of the boiler, I don't think it is original but has a sticker on it from 1980.
I cannot look down the roof but there is a draft up if I do a smoke test at the bottom.
Thanks
RE: 1929 Boiler
I worked a house where the boiler was dated 1885. Magnificent piece of work, forced hot air & steam system, complete with the original gauges, pressure valves. Reminded me of the Jules Verne movie 20,000 leagues under the sea, the Nautilus engine room. Oh, the boiler still works also, a newer system was installed about 50 years ago in place of the old one...Renaissance RestorationsVictorian Home Restoration Serviceshttp://www.renaissancerestorations.com
Yeah, its efflorescence, which indicates moisture is getting in there from somewhere. You should have the chimney liner inspected to make sure it's intact, but most likely what you have is rain moisture entering from the top and working its way down. I doubt that the automatic damper could cause it directly, but by cutting off the draft when the furnace is off it may keep moisture that gets in from the top from evaporating as readily.
I had the same thing in the last house I lived in. I posted the same question here (several years ago) and got the answer from several people that a liner was needed.
I put a liner in, and it helped. But it didn't make the problem go away completely.
I think it may have something to do with condensation. The bricks above the roof are cold in the winter, and ther's warmer air inside the house. So the bricks get some condensation in them either with or without a liner.
But that's just a guess. I suppose the best possible solution would be to frame a wall around the chimney to conceal the problem.
As you walk the roads of life, no matter what your goal. Keep your eye upon the doughnut, and not upon the hole.
Are you saying that the fireplace has been blocked off, meaning no longer used?
If so, cap that flue tight at the top. Rain water comes in, warm moist air shoots out in the winter and condenses on cold masonry surfaces. Could be the trouble.
Also, air leakage in chase around masonry flues often causes consensation that runs down the outside of chimneys. This gap should be sealed with sheet metal and RTV silicone at the attic floor.