Can you recommend a method of insulating regular 8-inch concrete masonry units that performs as well as an insulated 6-inch wood-frame house and is still cost competitive? Would rigid insulation on the exterior and veneer or lathe and stucco do the trick? I need some statistics to show comparisons. My area is in the White Mountains of Arizona: 7,000 feet elevation, -20º F to +88º F. This may help us get into the housing market in this area.
Following the chart shown here, you can build a concrete masonry wall with an R value equal to the R value of an insulated 6-inch wood-frame wall. Check with your local material suppliers for exact R values and prices of materials. Using molded expanded polystyrene or extruded expanded polystyrene instead of expanded polyurethane would provide R values of 7.00 or 10.00 instead of 12.50.
| INSULATION NEEDED TO GIVE 8-INCH CMU WALL SAME R VALUE AS INSULATED 6-INCH WOOD-FRAME WALL | ||
| 6-inch wood-frame wall | R value | |
| 1. Outside surface film | 0.17 | |
| 2. Wood siding | 0.81 | |
| 3. Sheathing felt | 0.06 | |
| 4. Plywood sheathing, 1/2 inch | 0.62 | |
| 5. Batt insulation | 19.00 | |
| 6. Gypsum plasterboard, 1/2 inch | 0.45 | |
| 7. Inside surface film | 0.68 | |
| Total | 21.79 | |
| 8-inch concrete masonry wall | R value | |
| 1. Outside surface film | 0.17 | |
| 2. Stucco, 3/4 inch | 0.15 | |
| 3. Lightweight concrete masonry | 2.12 | |
| 4. Cores filled with insulation | 4.85 | |
| 5. Expanded polyurethane rigid insulation, 2-inch | 12.50 | |
| 6. Gypsum plasterboard, 1/2 inch | 0.45 | |
| 7. Inside surface film | 0.68 | |
| Total | 20.92 | |
| SourcesMeans, R. S., Building Systems Cost Guide, 100 Construction Plaza, Kingston, MA 02364.Olin, Schmidt, and Lewis, Construction–Principles, Materials and Methods, Institute of Financial Education, 111 E. Wacker Dr., Chicago, IL 60601.”Thermal Insulation of Concrete Masonry Walls,” NCMA-TEK 38-A, National Concrete Masonry Association, 2302 Horsepen Rd., Herndon, VA 22070. | ||