Different insulation for different orientation walls?

[G-ManBart]

Okay, this may sound like a dumb question (probably is), but has anybody put more insulation in walls that face south/west to help minimize solar heating during the day?

I'm starting to insulate and cover the walls in my shop, and it occurred to me that I could put foam board insulation horizontally in between the 2x4s very easily. The majority of the south facing wall will be shielded from the sun by a 12' lean to, but the southwest corner will get sun, and the entire west wall will get sun for much of the day.

It would only take something like a dozen 4x8 sheets to cover the section I'm talking about, so it would be easily under $200.

For background, the floor has three 300' loops of Pex for radiant heat, with 2" foam board insulation underneath. The walls are getting R19 rolls since that's what fits, and the ceiling will be well pretty insulated...something like R45.

Similarly, the predominant winds come from the west, so extra insulation in that wall should help retain heat in the winter. I'm covering the inside with metal....picture below.

Any thoughts? Good idea? Waste of time?

 

[G-ManBart]

Anybody?

 

[DC73]

I think it's a good idea. It would be best to do all your walls but just doing those with the most exposure will help. The worst case would be an excessively long payback period for the additional insulation but it will eventually pay back. In your climate, I'd think the payback wouldn't take long.

DC

 

[CNGsaves]

+1 as good idea. I'd recommend scouting CL material section as I've seen those 1" sheets of 4'x8' insulation for $10 each, or less if you're lucky.

Since you're going with metal covering. it just means a longer screw !!

 

[dfiler2]

Yep, good idea.

 

[G-ManBart]

So I finally got back to this and took a couple of pics. Just FYI, I haven't insulated all the way around the window yet because I'm installing a mini-split there, and plan to run the linset in the wall cavity...have to order that soon. You can actually see where I added a section of 2x12 (it's what I had lying around) below the header where I'll mount the air handler.

Some folks have asked why I used 2x4s across the 4x6 posts, and that's because the header is attached to the posts similarly....so I needed the same thickness to line up with the header. This is the southwest corner. The OSB section is where a jackscrew door operator will go.

I went with R19 rolls in the voids, and then 1" Foamular (R5) between the 2x4s. It just seemed like a waste to have that gap and not fill it with insulation on the south and west walls. The east wall is an interior wall (insulated R13), covered with liner panels on one side and 1/2" OSB on the other. I think I'll have enough of the foam to do the north wall as well, but that's the least important. Unfortunately, I'll never know if it makes a difference, but I figured it can't hurt!

While I was hanging the fiberglass rolls (I did use fiberglass next to the door and under the OSB):




After:

 

[dfiler2]

Looking good. You won't be sorry for adding extra insulation.