Fireplace Sweating

[blowell]

Hi All:

I am in the process of having an entire home renovated. We do not live in the house yet. Yotul insert is installed in an exterior chimney and home is being heated by a gas-fired bodeen unit keeping the house at about 58 degrees for plastering. We live in New England, and the temp outside lately has been in the teens at night, and 20 to 30 during the day. We had a rain storm over the weekend. After the storm, I notice some water on the hearth - perhaps it came in at the top of chimney between stainless steel flue and the chimney itself somehow, I'm not sure. Inside of the stove is dry.

I go in the house today and notice that the brickwork above the insert is wet. The insert itself is wet with condensation, and the bricks above it appear to be wet is some spots, not with condensation, but as if water is seaping out from the bricks themselves. Not sure what is happening, but the water on the brickwork does not look like condensation, though waterever is happening, I am somewhat sure, is related to the difference in temperature between the outside or the coldness of the chimney and the inside of the house.

Any ideas as to what is specifically happening? Is this "sweating" normal? Should it go away once we get into the house and start heating and using the fireplace on a regular basis? The apparent leak is one thing, but this sweating is not something I've seen before. This home that we are renovating hasn't been lived in for about 3 years.

Thanks for the help on this.

 

[begreen]

Just a guess, is there a lot of plaster drying that is raising the moisture in the space? If so, this could be condensation.

If you can post a shot of the chimney top plate we might be able to spot an issue there. It sounds like perhaps it wasn't bedded in silicone to seal it.

 

[snowtime]

So many possibilities. First if you had the insert installed recently I would get the installers to check for leaks. Do not tell them about sweating they will only be interested in leaks. Its really tough to figure a problem like this when no one is living in home and able to describe problem on a day by day basis. If you got a new roof I would get the roofers to check for condition of flashing etc around the chimney. Usually sweating is caused by a lack of insulation and no or improperly installed vapor barrier.

 

[LLigetfa]

If the fireplace is connected to outside air, the flue could be drawing in cold air making the fireplace cold enough to condense the humidity. If the fireplace is installed in a masonry chimney and not well sealed at the flue, the flue could be drawing in humid indoor air and condensing it on the cold brick.

 

[blowell]

There is going to be alot of plaster drying, but mostly just blueboard in so far. Plasters have been mixing patch compound (or whatever it is) and it is everywhere, but a full room is not plastered.

This Yotul insert is installed in an exterior masonry chimney with a lue. I don't believe the chimney is insulated. I have called to have someone check the top of the chimney to see if leaking is occuring.

Just weird how just some bricks were wet - not even in the mortar, but in the middle of a few bricks themselves. I currently own a home with an interior masonry chimney, so this exterior chimney stuff is all new to me.

Thanks for the feedback, one and all. If I figure this mystery out, I'll post back with the info.

 

[My Oslo heats my home]

Just a guess, is there a lot of plaster drying that is raising the moisture in the space? If so, this could be condensation.

If you can post a shot of the chimney top plate we might be able to spot an issue there. It sounds like perhaps it wasn't bedded in silicone to seal it.

After I read the initial post I had the same first thought as green. Plaster curing releases alot of moisture into the air. The windows, concrete floors and brick usually show the most. The cold surface temps attract the moisture

 

[Install fire 1]

This is why i seal every insert at the damper.

The cold masonary chimney, and hot or warmer room air mix and cause condensation. This then runs down into the heat form, typically beaucse the clay tile sits on top of the form. I have seen as much as 3" of frost under a flashing on a chimney top without an insulated damper! Soaking wet, and running down to the bottom.

Where they meet is not sealed, and have seen water leaking out of lintel bars and wet surface materials.

Stop the cold and warm mix at the damper and they water issues should stop.

Anything on the outer glass or cast of the unit will be from the damp conditions from mudding the walls.

A bad flashing job around the chimney could cause severe leaks as the masonary soaks it up like a sponge, and wet goes to dry.

 

[blowell]

Thanks everyone who replied. I do believe it is primaily moisture from dryimg plaster.