Two inch versus three inch foam boards, I'd sure look at going three inches. What is the difference in R value? Is it foil faced?
Yep, going with 3". I couldn't get the pink foam in 3" thickness without ordering $1300 worth so I'm going to use a 2" thick piece of R-Max foil faced and glue a piece of 1" pink Owens Corning Foamular to it in order to get my 3". The foil faced foam has an R value of 1 greater than the pink stuff. A 3" thick "composite foam insulation will have an R value of around 19! I'll have the pink foam face the inside of the room and paint and texture to match the walls. I'll probably paint the foil facing outside white. I'm just about at the stage where I need to make this happen. I'm sanding the joint compound on the dry wall. Soon I'll be ready for texture.
From using foil faced in finishing my basement, I found that facing makes a significant difference. Any future insulating I might do, will definitely use that stuff.
Interesting. I'm not a professional carpenter, but I never though horizontal might be how some folks do it?
For your purposes, should not be any problem. Usually in a standard height room, horizontal. It adds a bit of strength to a wall and you end up with a bit less in joints to tape. If the structure has any tendency to expand and contract slightly, less chance of any troubles with seams. And you don't end up with long stripe seams, which might show in certain light angles- even with careful sanding and texturing such as spatter and knockdowns.
