Insulating R5 'Penitentairy tile' walls
I live in a 1 floor + full basement 1929 home, pitched roof with old Spanish tiles on top. The walls are plaster/pen-tile/stucco. 'Pen tile' is a hollow (3 chambers) brick block about the size of a toaster. I did some math, calculated that these walls are about R5. The steam radiators and solar gain keep the south side of the house warm, but the north side is pretty cold in the Albuquerque winter. There are 3 layers of attic insulation and I've fixed most of the air leaks. I have exterior storm windows. I had a door blower test that helped me find all the leaks. I plan to live here another 30 years or so. I'm considering increasing the comfort and lowering heating/cooling costs by adding insulation to the walls.
I've gotten all kinds of advice:
- build a new foundation outside the existing foundation and build a new wall on top
- screw ridged foam insulation to the outside of the walls, stucco onto the new foam.
I figure that putting insulation outside of the R5 brick will insure that moisture diffusing from the inside will hit the dew point in the middle of the foam insulation.
I'm not sure about screwing foam to existing stucco and having it hold the new stucco in place for another 40 years.
Any comments or questions welcome!