GREEN Insulation Retrofit
At each monthly meeting of the Green Home Builders of the Triangle (GHBT), a brief presentation is made to address a specific topic. This month featured "Insulation Retrofit Options", presented by Alan Spruyt of Trinity Design/Build.
New construction allows the builder to address the entire envelope of the structure, from attic to basement/crawl space. Retrofitting insulation into an existing home is much more problematic, particularly in historic buildings. While insulation can be fairly easily installed in attics and basements, the walls represent a much more serious challenge. In addition, while important, wall insulation does not contribute as much as other areas to overall energy savings, meaning that costs may exceed the potential benefits
The basic options are outlined below.
Option 1. Gut interior wallboard, insulate, and refinish Option 2. Gut exterior siding, insulate, and refinish These options have very high demolition and reconstruction costs, making them prohibitive if the sole purpose is insulation. If combined with other rehabilitation work which also require gutting the walls (electrical, structural, etc.), then the incremental cost may become realistic.
Option 3. Inject insulation This is a technically-sound process, but can be costly (foam) or risky (moisture-absorbing celluose). Again, costs may exceed benefits.
Option 4. Do nothing As it turns out, studies show that insulating the walls is less significant in creating energy savings than the other major components of the thermal envelope (roof, crawl, and windows). Even without insulating walls, upgrading the other components along with the HVAC system yields energy savings in excess of 50%, without incurring the high overhead associated with gutting walls.