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R30 Insulation Thickness Guide (Table for All Types)

R30 insulation is one of the more common insulation types that can be used and is often required in homes. As such, it is important to know as much as you can when it comes to R30 insulation and the requirements associated with it.

Here you will find descriptions of R30 insulation in your home and also the regions that require the use of R30 insulation. Best of all is the easy-to-read table, which offers different insulation types and how thick they would need to be to achieve an R30 rating.


R30 insulation is one of the most common ratings. It is used in ceilings in mild to warm climate zones and in floors and walls in cold climates. To achieve R30 with the thinnest layer, use closed-cell spray foam (5"). Using loose-fill fiberglass would require the thickest layer (12.5").

R30 Insulation Is a Very Common Minimum Rating

Ceilings

R30 insulation is a lower rating that is commonly used in ceilings.

Table N1102.1.3 of the International Residential Code (IRC) specifically describes when R30 insulation is required. In the case of ceilings, R30 insulation is required in zones 0 and 1. Hawaii is a zone 1 climate, as are Puerto Rico and Guam.

Zone 1 climate in United States: Hawaii, Guam and Puerto Rico

The United States of America do not have any locations in zone 0.

Such areas have a lower insulation requirement because the temperatures are fairly consistent and mild to warm.

As such, not as much insulation is needed because no extreme amount of heat needs to be kept out. And, because it is not as cold out, a great deal of heat does not need to be kept in.

R30 insulation stops between 96% and 97% of the heat that would get through via conduction.

Walls

On the whole, walls require lower R-value ratings, so the climates where R30 is listed for use in walls (see Table N1102.1.3) are very different to where it is required in ceilings.

Zones 4-8 (marine zone 4 included) require R30 insulation to be used in walls. States in these zones include Kentucky, Nevada, Ohio, Montana, Alaska, and some Alaskan boroughs are included in zone 8.

These zones require R30 insulation in their walls either because they are exposed to very cold climates constantly, or they have the potential to encounter such temperatures.

In these areas, R30 is required so that heat is retained in the home. In such zones it would be rare that the goal of R30 insulation in the walls is to keep heat out, except in zone 4, which runs along the northern portions of the southern United States.

Floors

Table N1102.1.3 of the IRC describes when R30 insulation is required in floors as well. Again, R30 is quite a high rating when it comes to floor insulation.

Zone 5, marine 4, and zone 6 are the only ones that require that R30 insulation is used in the floors. States in these zones include Nevada, parts of Washington state, parts of Oregon, and Montana.

It is important to note that zone 4 (excluding marine zone 4) does not require R30 insulation in their floors. This would include a state like Kentucky.

Man in PPE installing mineral wool insulation on the floor at the attic

These areas require R30 insulation in their floors because it is a little thicker and these zones are exposed to somewhat colder temperatures. And with having the insulation in the floors, the goal is to keep heat in the desired areas of the home.

Only Some Climate Zones Require R30

Zones 0, 1, and 4 through 8 (including marine zone 4) in some fashion require the use of R30 insulation, whether ceilings, floors, or walls.

The only zones that don’t require R30 insulation in any facet are zones 2 and 3. Some states that reside in these zones are Alabama, most of Florida, and most of Texas.

These areas don’t require R30 at all because of the intense heat they are normally encountering. As such, the insulation that is required is either thinner than R30 or thicker than R30.

Insulation thicker than R30 is required in these climates (specifically in the ceiling) so that temperature control (e.g., air conditioning) can more effectively be kept in the house. And insulation thinner than R30 is used so that heat within the house can more easily pass outside of it.

R30 Insulation Thickness Guide: Table

Insulation TypeInherent R-value (per inch thickness)Thickness to achieve R30Best-selling option
Loose-fill fiberglass 2.2-2.7± 12.5″Owens corning 19
Loose-fill mineral wool3-3.3± 9.5″R15 comfortbatt
Loose-fill cellulose3.2-3.8± 8.6″Borate only cellulose
Fiberglass batt (amazon link)3.1-3.4± 9.4″Knauf insulation EcoBatt
Mineral wool batt3-3.3± 9.5″Havelock Wool
Plastic fiber batt3.8-4.3± 7.3″JM Comfort Therm Fiberglass
Natural fiber batt3.4± 8.8″Owens Corning
Open cell polyurethane spray foam3.5± 8.6″ Loctite tite Foam
Closed cell polyurethane spray foam (amazon link)5-7± 5″Tiger foam
Foam boards3.6-8± 5.7″SilveRboard

Sources

https://www.tfofl.com/how-insulation-works

https://www.energy.gov/energysaver/insulation

https://www.energystar.gov/campaign/seal_insulate/identify_problems_you_want_fix/diy_checks_inspections/insulation_r_values

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