R-VALUE: 40.0, SUITABLE FOR: new construction, retrofitTHERMAL PERFORMANCE: At R-3.5 per in., the cellulose in this system yields an overall value of R-40.PROS:• Familiar building process means lower labor costs with readily available materials.• If cellulose is used, the project has a lower environmental impact.• Large moisture-storage capacity allows wall cavities to dry gradually.CONS:• Fairly involved insulation process can add to labor costs.• Reduces interior space by 3%.
Figure 7: Cavity Insulation with Vapor Barrier—Adding impermeable foil faced insulating sheathing over fiberglass cavity insulation is a hybrid approach that uses the best qualities of both materials. Note that the optimum location for the airspace is above the cavity insulation. Are you folks paying attention at the EPA ENERGY STAR® Program? Makes for warmer floors—this is the same detail that should be used under bedrooms over garages.