What is going on with this chimney?
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| Posted in Energy Efficiency and Durability on
I have a customer that has condensation around the lower 5 feet of the chimney in the walk up attic. See pics below. We dense packed the attic floor and airsealed around the chimney. They claim this never happenned before we did the work. It is a 1200 square foot space. The floor around the chimney has heaved and the ceiling below is wet and stained. Any help is appreciated.
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Replies
Phil,
I had a similar issue (white powder). It's most likely coming from the top-side - water flowing through the cracks and porous cap in the chimney. The hydronic pressure pushes the salts in the ceramic brick to the face.
I can't say why this suddenly occurred after your insulation job. Maybe sealing around the chimney prevented it from drying out as a result of air (heated even) passing over the surface. Once you stopped the loss of interior air from the living space, the water had no way to quickly dry out (hence the condensation).
If the white powder existed BEFORE you did your job, then it's most certainly a prior condition (faulty chimney).
I've seen lots of leaky chimneys and have to agree with Shawn. The efflourescence visible in the photo tells me that water has been moving in this brickwork for some time. Check the chimney cap for defects (cracked crown, no cover, bad mortar joints and spalling) A bad chimney cap can be repaired with high quality mortar or a sheet metal cap. Flaking of the brick surface is called spalling and is likely a worst case scenario for you. Just about everything on this list is best left up to a qualified chimney sweep. The best case is that the step/counter flashings at the shingle are defective.
Tony Olaivar- BPI Professional, Lanz Inc
Phil,
Is this an "orphaned" chimney -- a flue that used to exhaust gases from a furnace and a water heater, but which now serves only a water heater (because a new PVC-vented furnace was installed)?
If your work made the chimney colder, you have condensation because the flue is too big for the appliance, and too cold.
Phil,
Whats happening at the roof line?
Have you inspected the chimney crown~ is there a crown or flue liner in this chimney?
Is the chimney below the attic covered with plaster throughout the house living space?
Effloressence appears to have been occuring for some time, and blackened mortar joints could possibly reveal creosote being wicked or drawn through. Lots to inspect before a diagnose can be accurate. My suspicion is that the sealing and dence packing might have minimized the chimneys water infiltration drying ability, but the water infiltration problem was a pre existing condition.
Did anyone notice the "brick flakes" on the attic floor?
Something powerful is "blowing" the face off of the bricks.
My guess....
The Attic is colder and drier than before "improvements".
The area near the ceiling below is warmer and holds more moisture than before "improvements".
Since the WET concentration is near the floor of the attic...
Perhaps most of the moisture IS coming from below....
The brick+mortar+mortar cracks in the chimney are absorbing moisture from the living space....
Maybe when the fireplace is used ... the heat "Drives" the moisture out of the bricks.
just guessing
John,
When you have wet high suction brick, as these appear to be, a simple freeze thaw cycle is enough to spall or pop the face right off. I think you are right about heat from inside the fireplace driving the moisture out, but my experience with old chimneys and the things that they are attached to is that no 2 are alike and you really need to craw all over them to figure it out.
A couple of other things to think of. The attic is going to be cooler. When the furnace is off the chimney will coll faster and more. The furnace will also be running less too.
I wish the original poster would respond and answer the many questions that have been asked.
My guess is significant water leakage from above, most likely through the chimney cap but possibly through flashing.
The efflorescence suggests long-term moisture diffusion from inside to out, leaving salt deposits as the water evaporates. The spalling is more likely a result of the efflorescence which produces osmotic pressures that are typically greater than the strength of the brick.
I have not inspected the cap of the chimney up close nor the roof. The DHW is not orphaned and there is no fireplace. The chimney chase is enclosed all the way to the basement and is sealed at the basement ceiling and the attic floor. The chimney cap seems to be too small for the top of the chimney, but from the ground is hard to tell. I am trying to find possible explainations for the customer. All of your feedback seems to head in the direction of the chimney being the problem and us insulating the attic brought it to light. Thanks
I use binoculars for an initial inspection from theground sometimes.
Here is a picture of the chimney. There is also leakage inside at the roof. Last year I cleaned up the mess at the base of the chimney and airsealed around it as i thought the heat leakage around the chimney might be causing the problem. The pile of scale and brick pieces around the base after 9 or 10 months is more than it was at that time. There is also efflorecense in the basement.
I would recommend rebuilding the chimney from the roof up, and making sure it's lined properly.
That's what it's going to take for this one.
November remove~ replace through the roofline with stainless flex flue for propane gas FP insert.
Total labor - 14 man hours. 2 men 7 hrs ea. $480.00.Total cost to owner $830.00.
These guys should have installed protection to the roof shingles. Flashing is not complete yet.