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Discussion Starter · #1 ·
Hi folks,

I'm working on the top floor of my 1905 fixer upper foursquare in Pittsburgh, PA. One of the jobs is to make the temperature much more comfortable, as it has no problem reaching triple digits in the peak of the summer. I'll be adding a whole house fan to pull the cooler air from the lower floors, and I'd like to beef up the insulation in the attic.

The attic has faced fiberglass between the ceiling joists. I have no idea how many decades it has been there. It's covered in coal dust on both sides and the insulation facing is VERY brittle - it breaks on touch. I'm guessing this still has some insulating value to it, and I'd like to throw another layer of insulation on top. Question is: should I use a vapor barrier, or does the old and brittle kraft paper still count as a moisture barrier?

Any other suggestions or comments on prior experience welcome!

Ben
 

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The Kraft facing is a vapor retarder, yes. Your best bang for the buck will be to air seal any penetrations (electrical holes, ceiling boxes, around vent pipes, etc) with some spray foam and then simply blow in more insulation on top. You get more moisture problems from large air leaks than from slow migration. Also make sure you don't have bathroom vents simply terminating on the attic.
 

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Pull out all the old & start over. The paint on the ceiling also counts as a retarder so no worries there besides as stated above the biggest issue is actually the penetrations. A whole series on how to do thing properly: Air Sealing: Attic Floor Insulation (thehtrc.com) FYI code in your area is now or will soon be R60 - I would probably just go with a blown in product
 

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Hi Ben and welcome to the forum.

Be sure you don't have balloon framing that extends framing cavities from basement to attic. Stuffing them with fiberglass insulation does not block the air flow and there are fire blocking issues.

A whole house fan typically exhaust air from the house to the outside through the attic, is that what you are considering? Or are you just thinking to circulate inside air?

Do you have ac?

Now would be a great time to eliminate that old insulation as SLS suggests. Dusty, dirty and unknown what is hiding under it, dawn the masks, bag it, and vacuum the rest, you will sleep easier. More importantly it exposes the attic floor which allows for a great job of air sealing.

In summer you breathe a lot of air coming down through that attic. Cool air is heavy and falls to the lower portions of the house or basement an leaks out. It gets replaced by warm attic air leaking in through that dusty insulation. If you have ac it gets worse. In winter the flow reverses and you end up breathing air from the basement.

Bud
 
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Discussion Starter · #5 ·
Thanks for the advice, everyone. @Bud9051, to answer your questions:
  • I plan on cutting out soffit vents, with a total square footage recommended for the size of the whole house fan. I'll install baffles in the attic in proximity to wherever I install the soffit vents. Then add the additional insulation.
  • I don't have AC. I'll likely give the attic fan and improved insulation a couple of summers and decide after that. I have forced air heating, so adding an air conditioner isn't too big of a job down the road.
To me it seems like a bit of waste to tear out the existing insulation. I vacuumed all of the dust out of the crawl spaces behind the walls, and if I add a layer of insulation over the existing insulation, it seems like that would do a decent job of "locking in" the dust. Does this sound feasible? I hope I don't sound lazy!

Thanks for the heads up about balloon framing. I have never heard of the term, but have been told to keep an eye out for extended bays that could create a chimney effect. I've only broken into one section of an original wall, and from what I can tell, it is not balloon framing because there is a double plate running across between the first and second floor. That said, I'll take a closer look in the attic and see if I can hear things fall a long way in the original stud walls.
 
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