5 Inches Closed-Cell Spray Foam in Zone 5
Total R-value, DOE comparison, and upgrade recommendation for this attic insulation scenario in IECC climate zone 5.
Reviewed May 22, 2026
Total R-value
R-32.5
below DOE recommended minimum — upgrade recommended
DOE recommended: R-49 to R-60 · IECC 2021 code: R-60
Your attic insulation
Add one layer per distinct material in your attic (e.g., original fiberglass batts plus newer blown-in cellulose). Measure depth in inches at multiple points and use a typical value. Click Calculate to see your total R-value, status against DOE recommendations, an R-value gauge, and upgrade depth by material if needed.
Insulation layers
Layer 1
inches deep
Current total R-value
R-32.5
Climate zone 5 · DOE target R-49 to R-60
Below DOE recommendation
Your current attic insulation is below the DOE-recommended R-value range and below the IECC 2021 code minimum. Adding insulation is one of the highest-return envelope improvements available — payback is typically 5-10 years in heating-dominated climates and 8-15 years in cooling-dominated climates, much faster than the 25-40 year payback typical for window replacement.
DOE recommended
R-49 to R-60
Cost-optimal target for zone 5
IECC 2021 code minimum
R-60
Federal code floor for new construction
Add to reach target
R-16.5
Additional R needed for DOE low target
Where your R-value lands on the scale
The gauge below maps R-values from 0 to R-80. Your current total is marked, with the IECC 2021 code minimum and the DOE-recommended range overlaid. Most residential attic insulation work targets the DOE-recommended range as the cost-optimal end state.
Your current insulation layers
Each layer of insulation in your attic contributes its depth multiplied by its material's R-per-inch. Layers add in series — a layer of R-13 batt under a layer of R-30 blown cellulose totals R-43 at the center of cavity, ignoring thermal bridging through joists.
| Layer | Material | Depth | R per inch | Layer R |
|---|---|---|---|---|
| Layer 1 | Closed-cell spray foam (aged) | 5″ | 6.5 | R-32.5 |
| Total R-value | R-32.5 | |||
Upgrade to reach DOE R-49
You need to add R-16.5 on top of your existing insulation. The depth depends on which material you choose. Loose-fill cellulose typically wins on cost-per-R for attic floor applications; closed-cell spray foam wins where ceiling depth is constrained.
| Material | R per inch | Depth to add | Typical use case |
|---|---|---|---|
| Loose-fill cellulose (blown) | 3.6 | 4.6″ | Cheapest per R; settles 10-20% over 5-10 years |
| Loose-fill fiberglass (blown) | 2.3 | 7.2″ | Alternative blown product; lower R per inch |
| Closed-cell spray foam (aged) | 6.5 | 2.5″ | Highest R per inch; use where depth is limited |
Estimated annual savings from upgrading
Going from R-32.5 to R-49 reduces heat flow through the attic by about 34%, since heat flux scales with 1/R. For a typical 1,500 sq ft attic in zone 5, that translates to roughly the estimate below.
Heat flow reduction
34%
Through the attic, comparing 1/R-33 to 1/R-49
Estimated annual savings
~$57
At natural gas $1.30/therm, 95% AFUE, 1,500 sq ft attic; cooling savings additional
Estimate is illustrative. Actual savings depend on attic area, infiltration through the attic floor, duct losses, equipment efficiency, and local utility rates. For a precise number, run the Manual J load calculator at both the current and the upgraded R-value and compare the heating loads.
Air seal first, then insulate
Insulation slows conductive heat flow through solid surfaces. It does almost nothing to stop air leakage through gaps, holes, and penetrations. A house with R-49 attic insulation and 12 ACH50 air leakage performs worse than the same house with R-30 insulation and 4 ACH50.
The major air leakage points in a typical attic are: bath fan housings, recessed lights, plumbing chases, top-plate-to-drywall gaps, the attic hatch, electrical wires, and dropped ceilings over showers. Sealing these with caulk, foam, and gaskets typically costs $500-$1,500 in a 2,000 sq ft home and produces 10-25% heating/cooling load reduction — usually a bigger improvement per dollar than the insulation upgrade itself.
The right order of work is: (1) blower-door test to measure current leakage and identify worst leaks, (2) seal the worst leaks first, (3) verify with a second blower-door test, (4) then add insulation over the now-tight envelope.
What this calculator does NOT account for
- Thermal bridging through joists. Wood ceiling joists conduct heat 5-10× faster than insulation. The center-of-cavity R-value the calculator reports is the steady-state R between joists; the effective whole-attic R is typically 10-15% lower in standard wood-framed construction.
- Installation quality. The catalog R-per-inch values assume careful installation. Sloppy blown installation that fails to reach the eaves, batts compressed in undersized cavities, and wind-washing through soffit vents can reduce field-effective R by 20-30%.
- Settling of blown insulation. Loose-fill cellulose settles 10-20% over 5-10 years; loose-fill fiberglass settles 5-10%. Account for this by adding 10-15% extra depth at install.
- Moisture impact on R-value. Wet insulation has dramatically lower R-value than dry insulation. Confirm there are no roof leaks or condensation issues before insulating; add a vapor barrier if local code requires.
- Duct R-value, if ducts run in the attic. Ducts in attic space lose 20-30% of supply air through walls and joints. Sealing and insulating ducts often saves more energy than the insulation upgrade.
What this calculation is
Five inches of closed-cell spray foam delivers R-32.5 in a much thinner depth than blown materials — useful in cathedral ceilings or where attic depth is constrained. In zone 5, R-32.5 is below the DOE recommendation of R-49; more foam (or an added layer above) is worth considering. Spray foam costs more per R-value than blown cellulose.
How this R-value was reached
The total R-value of an attic is simply the sum of each layer's contribution. Each layer's R-value is depth × the material's R-per-inch.
- 5″ Closed-cell spray foam (aged) = R-32.5
- Total: R-32.5
Upgrade recommendation
To reach R-49 (the DOE recommended minimum for zone 5), add about R-16.5 on top of the existing insulation. Required depth varies by material:
- 4.6″ of Loose-fill cellulose (blown)
- 7.2″ of Loose-fill fiberglass (blown)
- 2.5″ of Closed-cell spray foam (aged)
What R-value doesn't tell you
R-value is steady-state conductive resistance. It doesn't capture air leakage (often the biggest energy loss in older attics), moisture-related performance loss, settling of loose-fill over decades, or compression from foot traffic on batts. Use this calculation as a baseline; combine with a blower-door test or an energy audit for a full picture.
Adjust the inputs
The calculator above is interactive. Change the climate zone, modify layer depths and materials, or add additional layers to see how the total R-value and upgrade recommendation shift.
Methodology
R-per-inch values are from the attic R-value article, cross-referenced with ENERGY STAR R-Value Recommendations and DOE Energy Saver. DOE recommended ranges are for existing-home retrofits; IECC 2021 code minimums apply to new construction. Material R-per-inch values are aged (settled) for loose-fill, normal for batts, and aged for spray foam and rigid boards.
Try other attic R-value examples
Compare to other depths, materials, or climate zones.
- 6 Inches Fiberglass Batt in Zone 5
R-18.0 · zone 5
- R-38 Attic in Zone 5
R-37.8 · zone 5
- R-19 Attic Insulation in Zone 4
R-18.9 · zone 4
- 12 Inches Blown Cellulose in Zone 5
R-43.2 · zone 5
- R-30 Blown Cellulose in Zone 4
R-29.9 · zone 4
Reviewed May 22, 2026