Insulation tools and calculators
By Insulation Report Editorial. Last reviewed August 2026. How we research this.
Three questions cover most of what a homeowner needs to decide about attic insulation: what do I have, what should I have, and what would the difference cost. The tools here answer them from published federal and manufacturer data rather than from rules of thumb, and each one shows its working. Climate zones come from the Department of Energy and Pacific Northwest National Laboratory county dataset for the 2021 IECC. Recommended levels come from ENERGY STAR. R-value per inch is carried as a range rather than a single number, because it genuinely varies by product and installed density, and a single figure would be false precision. Where a result rests on an estimate rather than a measurement, the tool says so on the result itself rather than in a footnote. None of these tools tells you what your local building code requires, because energy codes govern new construction and permitted work rather than a voluntary top-up, and adopted editions vary widely by state.
Available now
- Insulation depth checker. Measure what is on your attic floor and find out what R-value you actually have, how it compares with the level recommended for your climate zone, and how many more inches would close the gap. Includes a static depth to R-value chart for every common material.
How these tools handle uncertainty
Most calculators in this subject return one confident number. That is easier to read and it is usually wrong, because the inputs are ranges. Blown fibreglass is about R-2.2 to R-2.7 an inch depending on the product and how densely it went in. Loose-fill settles, so its R-value does not scale strictly proportionally with depth, a point the Department of Energy makes explicitly and most calculators ignore. About three percent of ZIP codes straddle a climate zone boundary.
So these tools return ranges, and they name the limits on the result rather than in a footnote. Where the decision is the same at both ends of a range, which it usually is, the range costs you nothing and tells you the truth.
What these tools do not do
They do not tell you what your local building code requires. Energy codes govern new construction and permitted work rather than voluntarily topping up an attic you already have, and adopted editions currently range from a 1989 model code to the 2024 IECC depending on the state, with home rule or voluntary adoption in several. Your local building department is the only authority on that.
They also do not price a specific job. A quote depends on access, clearance, existing condition, whether air sealing and baffles are included, and disposal, none of which a calculator can see.