- Upgrade windows: Window technology is changing rapidly. Typical single-glazed windows are the equivalent of R-1. Most double-glazed windows are up to R-2. There are windows on the market now that are as high as R-11 for fixed glass and R-7 for operable windows. Window-replacement economics change dramatically if you can improve the R-value that much.
- Inspect roofing and siding: As houses age and potentially settle, the cladding that protects the envelope can develop cracks or just wear out. When inspecting the exterior, keep in mind that exterior insulation can be installed before the new siding or roofing is applied.
- Upgrade wall insulation depending on age and style of house: Blowing in insulation in existing walls has potential problems depending on the construction employed when the house was built. The exterior felt paper may have disintegrated allowing water into the wall cavity. If there is no insulation now, any water that gets behind the siding can just evaporate in the wall and exit out as water vapor. If you fill the wall with insulation it will trap the moisture and can cause mold and rot to grow out of sight. Find an unobtrusive spot and cut a hole in the interior wall to see what the condition of the wall cavity is. Then make a determination about how to proceed.
When energy-efficiency retrofit projects are prioritized in the order of tightening the envelope and reducing air infiltration first, then any changes to HVAC equipment will be based on lower heating and cooling requirements because of the improvements. After all energy considerations have been exhausted, then solar and/or other renewable-energy systems can be discussed. As sexy as solar has become today, all of the previous improvements will give your clients the biggest bang for their buck. Solar simply is the icing on the cake.