Insulating a fireplace chase above attic

Reply

  #1  
Old 02-04-09, 10:11 PM
Member
Thread Starter
Join Date: Jan 2009
Location: Rochester, MI
Posts: 16
Insulating a fireplace chase above attic

We are still trying to get our pre fab zero clearance wood burning fireplace installed and we had a chase built for the chimney. The empty chase has been sitting on the roof open to the the attic since Dec. 2008.
The trussed attic is insulated sufficiently in most spots averaging 10-18". Ridge vents, Roof vents, Soffitt vents and a gable vent exist.
Builder says the chase does not need insulation since it basically a part of the roof and not within any heated areas. Frost has been collecting inside the chase, but that may be due to the intermittant, temporary openings in the attic for construction. We have never had frost before in the attic.

Do we put insulation in the chase or not, if so what kind?
How do we support it on the walls?
The chase is 24" sq. and the chimney is 8" diameter.
 
Sponsored Links
  #2  
Old 02-04-09, 10:20 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,399
Rather than insulation in the chase, which in my opinion would do absolutely no good at all, you might have the builder install a vent panel at the top of the chase to let out the moisture-laden air. I think a screened soffit vent of about 3 inches by 15 inches would work okay. Put it in the side of the chase and on the side away from the prevailing winds.
 
  #3  
Old 02-05-09, 01:22 AM
Member
Thread Starter
Join Date: Jan 2009
Location: Rochester, MI
Posts: 16
Good idea to vent, Insulating the chase seems to be like insulating the roof sheathing boards,correct?
 
  #4  
Old 02-06-09, 04:49 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,399
Yeah, like insulating the underside of the roof sheathing while also ventilating the attic. Or maybe like putting an electric heater in the refrigerator so the beer doesn't get too cold.
 
  #5  
Old 02-06-09, 05:32 PM
Member
Join Date: Sep 2005
Location: ohio
Posts: 195
Im not sure I understand your situation. Is the warm air coming from below in the space between the chase and the chimney? Surely the chase doesn't extend all the way to the roof does it? Is no chimney yet and you simply have an empty hole going down all thru the house? If this is heated air from the living space below, then yes don't put insulation there but do actually seal it off with sheet metal or some other type of non combustible flashing and use fire rated caulk for the flashing/chimney joint. If there is no chimney yet you can just close up the hole on top with foamboard and sprayfoam to temporarily seal it up until construction is complete. Also if moisture laden air is flying up the chase from the living area then you will definitely see frost in the attic.
 
  #6  
Old 02-12-09, 10:51 PM
Member
Thread Starter
Join Date: Jan 2009
Location: Rochester, MI
Posts: 16
Originally Posted by d00bs View Post
Im not sure I understand your situation. Is the warm air coming from below in the space between the chase and the chimney? Surely the chase doesn't extend all the way to the roof does it? Is no chimney yet and you simply have an empty hole going down all thru the house? If this is heated air from the living space below, then yes don't put insulation there but do actually seal it off with sheet metal or some other type of non combustible flashing and use fire rated caulk for the flashing/chimney joint. If there is no chimney yet you can just close up the hole on top with foamboard and sprayfoam to temporarily seal it up until construction is complete. Also if moisture laden air is flying up the chase from the living area then you will definitely see frost in the attic.
After I blocked off the chase with visqueen the chase did not get the frost inside of it. The chase sits on top of the roof shingles and sheathing. There is just a hole in the roof into the attic. The floor of the attic has the opening to the house that was covered with a board without a vapor barrier.

The chimney vent is now installed with an insulated firestop at the base in the attic. All openings have had vapor barrier reapplied below the insulation. At the roof line it sounds like I should put flashing around the chimney vent and caulk that, correct.?
It has not been cold enough since I sealed all the openings with a vapor barrier to look for for frost inside the chase.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes