In a confirmed Zone 5A home, use R60 as the uninsulated-attic comparison and R49 when 3–4 inches are already present. Buffalo is DOE’s example, not a local forecast.
What the official table recommends
| Condition | Guidance | Scope |
|---|---|---|
| Uninsulated attic | R60 | ENERGY STAR retrofit recommendation for the Zone 4C/5/6 group. |
| Existing 3–4 inches | R49 | Official retrofit table condition |
This table compares attic R-values. It does not calculate bags or measure the gap in performance. Assess the existing insulation first, then match the required added R-value to a current product label.
What to check through the year
- Spring
Inspect roof, attic, and drainage for damage or staining.
Moisture conditions must be fixed before top-up.
- Summer
Complete accessible air-sealing documentation.
Loose fill makes later access harder.
- Fall
Check attic hatch and insulation continuity.
Boundary gaps should be resolved as part of the assembly.
Before you plan the work
- Confirm the actual project zone using the cited official lookup or the authority that applies locally.
- Inspect existing material, moisture, air leakage, safe access, wiring, fixtures, and combustion equipment before top-up.
- Use the coverage chart on the current product label; do not transfer bag data between U.S. and Canadian products.
- Treat representative locations as classification examples, not local forecasts or code boundaries.
Sources and notes
Source links reviewed July 16, 2026. A review date is not the document's publication date.
- U.S. Department of Energy: Prototype Building Models — Climate Zone RepresentativesUnited States · government standard
Representative locations classify a zone; they are not a substitute for local weather or code data.
- Pacific Northwest National Laboratory: Guide to Determining Climate Zones by CountyUnited States · government standard
Use the county files for a project address; representative cities are examples rather than boundaries.
- ENERGY STAR: Recommended Home Insulation R-ValuesUnited States · government guide
Recommendations are presented by ENERGY STAR using 2021 IECC climate zones.
- ENERGY STAR: DIY Checks and InspectionsUnited States · government guide
Do not disturb suspected vermiculite insulation; obtain qualified guidance before work.