Most homes need R-30 to R-60 in the attic, R-13 to R-21 in the walls, and R-13 to R-38 in the floors, depending on climate zone. In cold zones, high R-value insulation systems mean R-49 to R-60 overhead. A residential insulation guide can help you identify the recommended levels for your home. Find your zone, check the chart below, and add insulation where yours falls short.
TL;DR
R-value measures how well insulation resists heat flow. So, what R-value do I need? It depends on your climate zone, the part of the house, and what’s already installed. This insulation R-value guide covers all three.
Materials are rated per inch, but codes use the total. Multiply depth by the per-inch rating, and remember building insulation R-values add up across layers. A lower-rated material can still hit your target if you install it thicker.
Start with the insulation R-value map. ENERGY STAR‘s map splits the country into zones 1 through 8, from hot to cold. A number that works in Zone 3 falls short in Zone 5, so look yours up first. New Mexico keeps its own city-by-city zone table, so check your town there too.
This R-value insulation chart follows ENERGY STAR retrofit targets for existing wood-framed homes. Read it as an insulation R-rating chart: pick your zone, then match the attic column to what you have now. Treat this R-value chart as a target, since local code controls new work.
| Zone | Bare Attic | Attic With 3-4 In. | Floor |
|---|---|---|---|
| 1 | R-30 | R-25 | R-13 |
| 2 | R-49 | R-38 | R-13 |
| 3 | R-49 | R-38 | R-19 |
| 4A, 4B | R-60 | R-49 | R-19 |
| 4C, 5, 6 | R-60 | R-49 | R-30 |
| 7, 8 | R-60 | R-49 | R-38 |
Heat rises, so the attic is the biggest opportunity in most houses. Attic insulation R-value targets are the highest in the home: R-30 to R-60 for a bare attic, and R-25 to R-49 if you already have 3 to 4 inches. Keep soffit vents clear as you add depth so the attic can still breathe.
Framing depth limits walls. Energy.gov notes 2×4 walls hold R-13 or R-15 batts, while 2×6 walls take R-19 or R-21. To raise wall insulation R-value further, add sheathing outside. When siding comes off an uninsulated wall, ENERGY STAR suggests R-5 sheathing in Zone 3 and R-5 to R-10 in Zones 4 to 8, after blowing insulation into the cavity.
Basement and crawlspace walls need moisture-smart choices. For basement insulation R-value, ENERGY STAR lists R-5 sheathing or an R-13 batt in Zone 3, R-10 sheathing or an R-13 batt in Zones 4A and 4B, and R-15 sheathing or an R-19 batt in Zones 4C and 5 to 8. Interior foam needs a half-inch gypsum board over it, and Energy.gov warns against open-cell spray foam below ground, where it can absorb water.
Your material decides how much depth you need. Rigid foam board delivers up to twice the resistance of most materials at the same thickness, per Energy.gov. Rigid insulation R-value commonly runs R-4 to R-6.5 per inch, while batts land near R-3 to R-3.7.
Closed-cell spray foam rates higher than open-cell and resists moisture, but it costs more. Loose-fill settles, so follow the bag’s coverage chart. Check the label, since federal rules require R-value disclosure.
New Mexico amends the model energy code, so the best R-values for insulation in New Mexico depend on your town and whether you’re building or retrofitting. The New Mexico Administrative Code sets ceiling minimums of R-38 in Zone 3 and R-49 in Zones 4 through 8, below the model code’s R-49 and R-60.
Those are new-construction minimums. ENERGY STAR’s retrofit table calls for R-60 in a bare attic from Zone 4A up, so colder-area homes may do better above the code floor.
A high label rating means little with a sloppy install. Energy.gov says to check three things on any job:
Seal air leaks before adding insulation, and don’t cram layers into a tight space, because squashed insulation loses R-value.
Not sure where your home falls short? High Country Solutions offers free quotes. Tell us which areas you want insulated and the R-value your zone calls for, and we’ll price the job. Call (307) 248-9063 or email [email protected].
Often, yes. R-values add up across layers, and ENERGY STAR’s attic targets assume you may already have 3 to 4 inches. Check that the old layer is dry first, because moisture hurts performance.
It won’t harm your home, but the returns shrink. Going past your zone’s recommended level adds cost with little gain in comfort or savings.
Yes. It slows heat moving in as well as out. That’s why even hot Zones 1 and 2 have attic targets of R-30 to R-49.
Some types, yes. Batts, boards, and pour-in materials are common DIY jobs. Blown-in insulation needs special equipment, and spray foam calls for a certified installer.
Material, access, and included air sealing all change the price, and quotes for the same R-value can differ by more than double. Compare written quotes line by line for R-value, depth, and scope.
