I have a customer that we dense packed the attic floor of their house and airsealed around the masonry chimney. The problem is the red brick chimney condenses in the attic. This has caused the floor around the chimney to heave and the ceiling below to stain. The attic is 1260 square feet and is pretty leaky to the outside. The customer states the problem has only occurred since we did the work. Can any one give me some ideas what would cause this issue?
The condensation is from the flue gasses condensing inside the chimney. This will be increase as the attic temp drops. ths cools down the brick which allows the flue gasses to condense out at a greater rate. If there is no clay liner or a flexible chimney liner in the chinmey one will neeed to be installed.
This has been happeneing before but because the attic was kept warmer do to the heat loss through the ceiling it would only have shown up when it got colder outside. Now that the attis is seperated from the house there is not enought heat to keep the bricks warm so more condensate from flue gasses is present.
The condensate is mildly accitic (like lemon juice) It will turn any paper products a dark chocloate brown after a while. This is one way to tell the difference between a roof leak and condensate.
All gas furnaces produce water vapor as a by product of combustion adn need to be addressed when furnace, water heaters and such are changed out- You will need to recommend a chimney liner.
http://oee.nrcan.gc.ca/residential/personal/chimneys.cfm?attr=4 the link will give you a explanation, even though it is canadian, they expriance the problems much more than warmer climates