Mark959 wrote:Also was thinking about using expanding foam in the ceiling ribs to help with insulation - anyone have thoughts or suggestions on that?
If you mean drilling small holes in the ceiling ribs (it looks from your pictures that they are ~1" square tubing style like mine) and injecting expanding foam in there, in my opinion, that has almost no positive effect in terms of thermal insulation.
The reason is that the tubing acts as a heat fin and will conduct heat around the insulation stuff in the middle, very similar to how it would conduct electricity around the insulation. (the industry term for this is "thermal bridging"). Also, the air inside that tubing will function as an insulator anyways since there isn't enough space for convective air currents. So replacing that air "insulation" with foam insulation will have little effect on the insulation value of the inside of your tube - which doesn't really matter anyways, because heat is going to ignore the inside of the tube and just go around it.
Anything you can do to introduce insulation material *in between* the ceiling ribs and your inner surface will help - your wood blocks will help somewhat, for example.
Now, using expanding foam *around* the ribs should help, particularly if there are any little gaps and crevices between your foam board insulation and the ribs. However I have no experience with using foam that way and can't advise specifics. I am just using foam board and tape to seal everything up as I chose not to fuss with expanding foam products.
Note: I have no data or personal experience with injecting foam into 1" metal tubing. My opinion on it is based on all my courses in heat transfer in mechanical engineering school where I did a lot of analysis on thermal bridging in walls, and my work in the building industry where we help architects design envelope detailing to reduce thermal bridging. Most people severely underestimate the impact that thermal bridging makes on the thermal performance of walls - until you run the numbers and collect the data, your intuition is almost certainly going to be wrong. Mine certainly was!
PS If your ribs are not 1" rectangular tubing, but rather sort of U-shaped, then injecting foam up in there might have a small positive insulation effect.