This insulation r value chart pulls the recommended levels for attics, walls and floors into one place, so you can pick a target in seconds instead of decoding a building code. The figures are simplified typical recommendations based on US Department of Energy and Energy Star guidance for the eight US climate zones — a planning chart, not a substitute for your local code. Once you have your target number, the insulation calculator turns it into a depth and a bag count based on what is already in your home.
What R-value means
R-value is resistance to heat flow. It is earned per inch of material and added up over the full thickness installed, so a higher R-value means heat moves through the surface more slowly: a wall at R-21 loses heat more slowly than the same wall at R-13. Because the number belongs to the whole installed layer, R-values stack — two layers rated R-13 and R-19, laid together without gaps, perform at about R-32. Every figure in the chart below is a total for the finished surface, not a per-inch rating, which is why attic numbers look so much bigger than wall numbers: there is simply room for more inches.
The chart: recommended R-values by climate zone
Here is the chart itself, in three small tables. These are simplified typical recommendations based on US DOE and Energy Star guidance — the levels most existing homes should aim for when insulating or topping up. Find your zone, then read across to the surface you are insulating. Where a range is given, the lower end suits the milder part of the zone and a tight budget; the upper end suits colder exposures and spaces that are cheap to fill, like open attics.
Attic
| Climate zone | Recommended attic R-value |
|---|---|
| 1 | R-30 to R-49 |
| 2 | R-30 to R-60 |
| 3 | R-30 to R-60 |
| 4 | R-38 to R-60 |
| 5 to 8 | R-49 to R-60 |
Walls (cavity)
| Climate zones | Recommended wall R-value (cavity) |
|---|---|
| 1 to 2 | R-13 |
| 3 to 5 | R-13 to R-15 |
| 6 to 8 | R-15 to R-21 |
With walls, the framing decides what physically fits. A 2×4 stud wall has a 3.5 inch cavity and takes batts of R-13 to R-15; a 2×6 wall has a 5.5 inch cavity and takes R-19 to R-21. Colder zones effectively reach beyond the cavity figure by adding continuous rigid foam over the outside of the sheathing, rather than by stuffing the cavity any harder — compressed insulation loses the R-value its label promises.
Floors over unheated space
| Climate zone | Recommended floor R-value |
|---|---|
| 1 | R-13 |
| 2 | R-13 to R-19 |
| 3 | R-19 |
| 4 | R-19 to R-30 |
| 5 to 8 | R-25 to R-30 |
These figures are for floors above unheated basements, crawl spaces and garages. A floor over a heated room needs no insulation at all — the heat it lets through is still inside the house.
Which zone am I?
Roughly: Zone 1 is the deep south — south Florida and the southern tip of Texas. Zone 4 covers much of the mid-Atlantic and the southern midwest. Zone 6 takes in northern New England, the upper midwest and Minnesota, and Zone 8 is Alaska and the coldest northern tier. Zones are drawn by county and the boundaries do not follow state lines, so check the US DOE climate zone map for your county before you commit to a target — then run your own numbers in the insulation calculator.
How to use the chart with the calculator
Three steps turn the chart into a shopping list. First, pick your target from the chart above for the surface you are insulating. Second, measure what is already there: depth multiplied by the material’s R-per-inch gives its current R-value, a method explained step by step in our guide to how much insulation do i need. Third, remember that the difference between the two numbers is all you buy. Enter that gap into the insulation calculator with your area and chosen material, and it returns the added depth and the number of bags. Topping up is normal: an attic sitting at R-19 in Zone 6 needs roughly R-30 more to reach the recommended range, not a whole new R-49 install.
Diminishing returns, honestly
More insulation always slows heat loss, but each step buys less than the one before, because heat flow depends on the thickness you already have rather than falling in a straight line. Lifting an attic from R-5 to R-19 transforms a house: bills drop, rooms even out, draughts calm down. Lifting the same attic from R-49 to R-60 is a small final step that might save a percent or two. That is why the chart gives ranges instead of single numbers, and why the sensible order of work is: air-seal first, bring the worst surface up into the chart’s range, and only then chase the top of the range if access is easy and the material is cheap. The measuring method in how much insulation do i need shows how to find your starting point before you spend anything.
UK and international note: U-values
Outside the US, the same physics is usually expressed the other way up. The UK and EU rate whole elements — a complete loft, wall or floor build-up — by U-value: how much heat passes through each square metre for each degree of temperature difference, in W/m²K. Lower is better, the exact opposite of R-value. The common UK recommendation for a loft is about 270 mm of mineral wool, which works out to a U-value of roughly 0.16 W/m²K. To convert between systems, an imperial R-value is about 5.68 times the metric RSI value, so an American attic at R-49 is roughly RSI 8.6 — handy when a product datasheet only gives one of the two.
Frequently asked questions
What R-value should my attic be?
Find your climate zone in the chart above. Zone 1 attics do well at R-30 to R-49, the middle zones aim for R-38 to R-60, and Zones 5 to 8 should reach R-49 to R-60.
Is higher always better?
Up to the top of your zone’s recommended range, yes. Beyond it, each extra R-point saves less energy than the one before, and the money usually works harder spent on air sealing or on the worst-insulated surface in the house.
R-value vs U-value?
They describe the same physics from opposite directions. R-value measures resistance to heat flow, so higher is better; U-value measures how readily heat passes through a whole element, so lower is better. Imperial R is roughly 5.68 times the metric RSI value.
Do R-values of layers really add?
Yes, when the layers are installed without gaps, voids or compression. R-19 of batts under R-30 of blown insulation performs at about R-49 — but compress either layer into a thinner space than it was made for and its R-value falls.