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?

Views: 2290

Attachments:

Reply to This

Replies to This Discussion

It seems to me the chimney is probably cold, being connected to the outdoors.  So the moisture is coming from the surrounding air.  If keeping moisture out of the surrounding air is not practical, I'd suggest insulating the chimney with fiberglass batts with a vapor barrier on the outside.  Does that sound reasonable?
Is the chimney lined? It could be from flue gases from an unlined chimney. Any problem with condensation on the roof sheathing?

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

RSS

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network.

Latest Activity

Profile IconDavid Lopez, John Doe and Ariston C. Hernandez Jr. joined Home Energy Pros
1 hour ago
David Eggleton commented on David Eggleton's group Considering Permaculture &/or Transition
"Are you on Facebook?  Are we friends there?  If not, please send me a request."
6 hours ago
Jan Green replied to Sandra K. Adomatis, SRA's discussion Green Mortgage Appraisal Roundtable
"Thanks for sharing Sandy!  As the AI industry guru in green, it's always wise to read…"
6 hours ago
Kevin Jordan posted photos
7 hours ago
scottscontracting posted a discussion
10 hours ago
tedkidd replied to Damien Greenfield's discussion Is there is cost saving for you in having a tankless water heater?
"Bob, here is where our perspectives diverge. I think people should switch to electric because they…"
yesterday
tedkidd replied to Damien Greenfield's discussion Is there is cost saving for you in having a tankless water heater?
"Here our thinking falls out of alignment. Going to electric is default for me. People can't…"
yesterday
Bob Blanchette replied to Damien Greenfield's discussion Is there is cost saving for you in having a tankless water heater?
"If you are going to stay with gas service, might as well keep the gas water heater. Switching gas…"
yesterday

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service