I'm getting closer to doing drywall, and looking for suggestions and opinions.

My house is a 'cinder block' constructed home, built in the70's. There is no exterior siding, and no interior wall treatments at all. Cinder block inside and out. I am on the north Oregon coast.

What I have already done is insulate the entire perimiter of the exterior walls (I insulated on the interior side of the walls) with a foil faced and foil backed insulation board "poly-iso"  and thanks to the input I got here, I put the insulation up first, completely covering the existing walls, then added framing on top of that, so as to not 'short circuit the insulation. I laid up 2x4 framing laid flat so I have only added a total of 3 1/2 inches to the wall thickness (2 inches poly-iso, 1 1/2 inches wood framing)

My dilema is: what should i do with the airspace? Leave it alone, or add another 1 1/2 inches of insulation? The foil facing on the existing insulation is supposedly designed to act as a radiant barrier, but likely will only work if it has an airspace.

So what would be best... adding the insulation, or taking advantage of the radiant barrier?

PS The climate here is mild, but long wet winters necessitate more of a 'heat load' than a 'cool load'. (Rarely does anyone here have AC)

Thanks

Mark

PS Also, the suggestion was given to insulate the exterior rather than the interior, but lack of funds did not allow that option. I hope to someday add exterior insulation and then add new siding over that.

The benefit of the air space & radiant reflective surface is worth FAR less than the ~ R5/R6 you'd get out of stuffing the shallow cavity with any fiber insulation, bringing your center-cavity R up to something like R19. INSULATE IT. Reflective insulation is much more useful on the exterior, where the temperature differences can be large enough to matter. Under the most severe conditions it might be worth R3, and the rest of the time less. The fiber insulation will be pretty much the same R value no matter how hot/cold it is outside, when placed on the interior side of the iso.

From a thermal bridging point of view it would have been better to use 2x3 or 2x2 rather than flat 2x4s, but it's not worth ripping them down an re-doing it.

If the spacing between the stud edges is 14.5" you could buy unfaced R13 batting and split them. If the spacing is odd-dimensioned it's probably easier/better to dry-blow cellulose into the cavites after you've put the wallboard up, but before taping & mudding it, or putting kick-board up. drilling one hole very near the floor and the other very near the ceiling you might be able to do it without having to do a super-cosmetic patch. (Drill them with a hole saw at any rate, and the patching is much simplified.) With the foil-face iso, do NOT use any type of batts with facers, or interior vapor barriers such as poly sheeting (or vinyl or foil wall paper).