Paul, we were in a very similar situation re: attic insulation. Our house in town is a 1950s brick and block bungalow with no wall insulation, just brick, block and (mostly) plaster walls that do act as mass. We have insulation in between the floor joists. The attic was woefully under insulated, with the original rock wool, and R19 batting rolled out in between the joists over that. It was in good shape, there just wasn't enough of it.
In Feb 2011, we had a professional contractor install a radiant barrier in our attic. My husband and I considered doing it ourselves but there are a few tight places that looked like a divorce waiting to happen. Also we didn't have easy access to the better quality radiant barrier that the contractor uses: a heavy duty reflective surface on both sides with insulation in between, sewn together leaving large enough stitch holes to provide for ventilation to prevent moisture build up. We had our attic "tented," i.e. the reflective barrier was attached to the gable walls and to the roof joists. We can walk, standing up, from one end of our attic to the other over the main part of the house. That area, right under the roof ridge, is floored in, and we use it for storage. So we had the barrier installed on the roof and gable walls so we could continue to use the attic for storage. The "tight" areas that we don't access anyway were "blanketed," i.e. the radiant barrier was simply laid on top of the insulation already present.
It took the contractors less than 4 hours to install the radiant barrier in our entire attic, and nary a cross word was said between the husband and me. Money well spent, in our opinions.
It was a cold, gray February day, and there was a cold front moving in. We had the pellet stove running but we had the thermostat turned down on the gas furnace so it wouldn't cut on. Even before the contractors were completely finished installing the radiant barrier in the entire attic, we watched the temperature in the house slowly start to rise... from just the pellet stove... no furnace... even though the temperature outside was dropping.
After they were done with the radiant barrier, we decided to go even one better on the attic insulation: we went to the local Big Box Home Improvement Store and bought rolls of R30 batting. My husband rolled it out crosswise, at a 90' angle to the ceiling joists and the insulation in between them. So now we essentially have R49 in batting insulation, plus whatever remains of the rock wool under that, plus the radiant barrier on the underside of the roof and the gables. Yeah, it's overkill, I guess... but it's also awesome. It really helps in the summertime, when we have an unimpeded south/southwest exposure on the roof.
It was absolutely delightful, at the end of that day, to close the attic door and watch the HVAC thermostat continue to rise with no heat source other than the pellet stove.
OH- and don't forget this part either- my father in law made us one of those insulated boxes that goes over the door for the attic opening... it eliminates that "chimney draft" around the attic door!
. I'm thinking of going with closed cell spray foam or at least flash and batt. I'm still trying to figure out what will work best.
