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-   -   sealing gap around furnace flue in attic (http://www.diychatroom.com/f103/sealing-gap-around-furnace-flue-attic-191431/)

Dave Sal 12-03-2013 07:11 PM

sealing gap around furnace flue in attic
 
4 Attachment(s)
Some of you may remember my previous post where I asked about sealing the furnace flue gap in the attic, as well as the bottom of the chase above the furnace itself.

http://www.diychatroom.com/f103/gap-...e-flue-190345/

Well, today was the day to take care of this in the attic as it was bugging me all this time. What I thought was about a 2" gap around the flue turned out to be much larger and made my opinion of the builder of this house go down even further. The gap on the far side was huge, probably 4"-5". I had made up two sheets of sheet metal with half moon cut outs that I was planning on sliding snug up against the flue from either side, along with a sort of flashing to keep the insulation away from the flue, but neither worked out as planned. Typical. On the closest side of the flue I was able to use one of my half moon sheet metal pieces after trimming some of one side away and then used hi-temp caulk to fill in the gap around the flue. So far so good. Then I moved the insulation away from the back side, which was hard to reach as I had to lay on my stomach to reach it, and found that the builder didn't even bother to frame in the area around the flue. They just mounted two aluminum bars across the studs on either side and ran two screws thru it into the flue to hold it in place. The gap on the far side was so big that I dropped the other half of my half moon sheet metal piece down the gaping hole, never to be seen again (you can see it in pic #3 at the bottom of the hole). I ended up taking a flat sheet of 14" wide sheet metal and laying it over the gap butted up against the flue after trimming a rough circle in it. Here are a few pics for your amusement. Imagine how much heat has entered the attic each winter through this area. The only good thing about this is that I am now done climbing in the attic. Never again. :whistling2:

jklingel 12-13-2013 01:30 AM

did you ever look into using roxul around that gaping hole? it sure looks like a ton of heat will be running up there, as well as water vapor. not a problem in your case? just a thought.

Windows on Wash 12-13-2013 05:47 AM

Good follow up.

You would be amazed at how some of these chases are constructed. You could put Jimmy Hoffa in some of these things.

old_squid 12-14-2013 10:08 AM

They're called a chimney in a chimney.


Just kidding. But it is how they function especially if there is an air passage way from the home/basement directly to the attic.

Gary in WA 12-14-2013 12:06 PM

Good you used metal for an air barrier as Roxul, fiberglass, cellulose or other fibrous cavity insulation types are not air-tight or meet minimum code in this application. You could improve slightly on your design by over-lapping one side metal piece for an area to lay the caulking bead on- catching both surfaces/sides for optimum contact just by shifting one metal onto the other when drawing the pattern circle. Now, get back up there again! Just kidding........ Good job!
http://www.buildingscience.com/docum...rent-this-time

Gary

Dave Sal 12-14-2013 12:39 PM

1 Attachment(s)
Actually Gary, I did cut a piece of sheet metal that overlapped on each other, but I didn't take a picture of it. The pic of the sheet metal flashing was my first version before I realized I needed to have it overlap.

I am going to add Roxul to the chase opening in the utility room and then seal it with more sheet metal between the joists. It'll be much easier getting access to it and should stop the majority of heated air from rising to the attic. It snowed here last week and most homes have snow covered roofs. But, driving around looking at roofs and it's amazing to see how many have absolutely no snow on them after completely melting. The large icicles on the gutters are another indicator that these homes lack adequate insulation or attic venting. Fortunately, my roof is still nice and snow covered. :thumbsup:

My latest energy saving project was making an insulated fireplace insert to block the cold drafts coming into the family room. I installed it the other day and I can actually feel the difference. The room used to be chilly all the time as it is below grade, but now it's noticeably warmer and the chill is gone. I still need to sand and stain it but may wait till spring so I don't have to smell the off-gassing from the stain. Now I need to come up with a new project to keep myself busy.

Gary in WA 12-14-2013 10:53 PM

You have to be careful around here when posting pictures.... lol. You passed the snow test= A+ you may now advance to more adventurous projects!

Later, Gary


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