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2nd floor overhang not insulated properly

13K views 15 replies 6 participants last post by  mjzraz 
#1 ·
I have a 2 story home with a 1 foot overhang for the 2nd floor. I was suprised to find a 3' piece of paper faced R-11 looped over itself and stuffed up in the joist space. There are a lot of air gaps.

My solution is to block off the joist cavity with 1 1/2" Rigid foam and caulk all the edges and then add a second piece against the subfloor, isolating the overhang area, stopping airflow and insulating. That will leave me with a 6" space left where I will use fiberglass batt inslation, or Roxul batts.

Pics:



Foam:

 
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#9 ·
Good read. That link seems to be more specific to the moisture issues in a crawlspace. I will have to explore that website more. Thanks.

Spray foam is a better solution, then the job that you did. It will not even keep the space warm in the winter.
Better, I would agree, but DIY? My foam is tight against the framing and the subfloor. I cut each piece individually for a friction fit and tapped it into place with a block of wood and sealed it with exterior caulk. In the areas with ducts, I taped the joints with metal duct tape and used 1 can each of expanding foam to fill the cavity and surround the duct. I checked from the inside to make sure the vents were not stuck or the duct crushed or blocked. I cut my foam sheets to fit around the duct and sprayed the expanding foam to seal them in.

Before doing the work I could feel cold air blowing out of the joist cavities and where the ducts were, was where I stood outside to cool off while working. The insulation was dirty and haphazardly installed. Afterwards there is no air escaping.

The R value of the foam insulation board is 7.5, I am using a roxul batt in the remaining space which has a R-23 and there is zero air flow and my ducts are sealed. So won't R-30 with zero air flow keep my space warm in the winter?

Roxul: http://www.roxul.com/files/RX-NA-EN/pdf/ComfortBatt_Sell Sheet_US.pdf

You should be “very concerned” with the exposed sheathing behind you vinyl siding.

If they missed it there then what else did they miss?
That's the story of my life with this house. partial list of minimium code or lousy work:
No window and door flashing
no building paper/WRB
Floor joist cut completely through for drain pipe and not braced
2nd floor joist cut for plumbing and "cosmetically braced" (the braces didn't actually touch adjacent joists - wtf?)
Wiring and plumbing penetrations in lower 1/3 of joists
2x8 spanning 14'
3/8 ply on 24" center roof sheathing
 
#8 ·
Only if you have one living under a bridge in your backyard. If the bats where stuffed improperly, two ways that could of happened: 1) Sub paid by the house, and their hired labor ready guys do not know, nor care how to place installation. 2) Prev. home owner did not know how to place bats, and made an attempt to try to stop cold air inflitration.

Spray foam is the proper way to insulate the overhang, not foam board.
 
#13 ·
That stuff is sheathing not wrap or building paper

It's a fiberboard sheathing from Georgia Pacific.

Not sure if it's the same stuff, but here is their current product:
http://www.gp.com/build/product.aspx?pid=6055

This house is from the early 80's. There is plywood on the corners - I assume for structural support since the fiberboard won't even hold siding nails.

I would like to replace it where I am replacing a sliding glass door and a window. Not sure if 5/16 osb or 1/2" plywood (4 ply CDX) is better...
 
#15 ·
the siding is aluminum if that matters. I am on the east coast, MD. I think I am convincing myself to go CDX. There is some rot, but it's from the aluminum slider frame and no flashing/sill pan and possibly the old deck ledger contributed as it was not flashed...

I'm using dupont flexwrap for the sills and 30# felt with a self adhesive (undecided on brand) to flash the sides of the new door and one new window. Here's the damage:


repair in progress:
 
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