Case Study - Rim Joist Insulation Problems

Did an inspection, for a General Contractor, no less. He did a 2nd floor addition to his house. Put in OSB I joists to support the 2nd floor. He called me to do an energy audit of his house ($375.00). The main problem was air infiltration at the 1st and 2nd floor top plates, but there was an interesting finding.

The OSB I joist ran from the front to the back of the house. See these pictures:

  1. Rear view of the house. Note the slight increased temp just above the where the 2nd floor addition is (vinyl siding).

  2. Interior pictir of the same area. Note the cold areas at the ceiling / wall interface.

  3. Picture of the ceiling at the center of the room. Note that the area between the joists is colder. Cold air infiltrating (actually, hot air exfiltrating) around the can light.

The rim joists were not insulated and sealed, allowing cold air to come into the inter joist spaces and make the 1st floor ceiling cold.

Feel free to swipe these images for educational purposes.

Hope this helps;




Will, what type of siding was that and how old was the original house?

Original (1st story) was built in 1992. Addition (2nd story) was added in 2005. Vinyl siding on the top with concrete brick veneer on the 1st floor.

Great example Will, how do you know that the rim joists were not insulated or sealed?

And, in this application, what is your opinion on insulating/sealing these two floors with 1. Closed cell foam or 2. open cell foam insulation?

I did not, eyes on, inspect the sealing of the rim joists.

But you know what?

I don’t have to.

The client was also the builder and even he did not know what his subs did :mrgreen:

But he totally understood and believed that it was messed up.

My opinion?

Get an architect (which he didn’t) to detail it (and take the liability, if it is wrong) and a good, licensed and INSURED (can you say E&O?) contractors to do the work.

My job is to inspect and report, not to fix or describe how to fix :cool:

They don’t pay me enough to do that.

Get my point? :wink:

Oooooooops! Good point to consider! :slight_smile:

Maybe we should be!?!??!?

Just kidding.
We can only do what the market will bare.