What is R-Value

Since you’ve owned a home or property, you have probably heard about a lot of terms and names you’re not familiar with. Specifically one important energy-saving term. So you might be asking yourself, just what is R-Value? Well, R-Value is a formula that divides the temperature difference between a barrier’s warmer and colder surface by the heat fluctuation through the barrier. In simpler terms, it measures the insulation’s resistance to heat flow.

Different types of insulation have varied effectiveness per inch of material, and every type has a specific R-Value. Each section of the home has an R-Value range determined by geographical and environmental factors. This includes walls, attics, floors, and crawl spaces.

The chart for R-Value for Insulation.

Each climate zone (ex. cold northern climate, hot southern climate, etc.) has recommended R-Values to ensure effective insulation. 

For example, based on the insulation r-value chart from Energy Star, if you are insulating your attic located in Zone 4 and the type of insulation chosen has an R-Value of R-5 per inch of thickness, you would need about 8 inches of insulation.

Walls using different sizes of wood have different R-Values as well. A wall constructed with a 2×4 has an R-Value range of R-13 to R-15, while a wall constructed with a 2×6 has an R-Value range of R-19 to R-21.

Why is R-Value important?

Using the recommended insulation thickness is important to your home for a number of reasons. For one, having the right materials and thickness will help keep cool air in during the hot summer months and warm air in during the cold winter months. In turn, this helps to conserve energy and also lower your electric bills and carbon footprint. Using the recommended insulation amount can help you save money in the long run. Look at your initial home insulation cost as an investment for all future energy bills you receive. 

What are the R-Values of different types of insulation?

The R-Value per inch of insulation varies depending on the type and brand of insulation. When installing insulation, considering the different types and their R-Values is important. If you live in a colder climate, choosing an insulation type with a higher R-Value could save you money because less material and heating are needed.


The table below shows the range of R-Values based on the type of insulation, affected by different brands:

A table that shows the R-Value for different types of insulation.

What is the best type of insulation?

While fiberglass and cellulose insulation has been used for decades, foam insulation takes the cake for being the most effective and safe material. Foam typically has a higher R-Value:

  • Keeps air from squeezing out of cracks and crevices
  • Won’t get caught on wiring or pipes
  • Won’t settle over time 
  • Resists mold and bacteria
  • Reduces air infiltration
  • Is smoke and fire retardant
  • A highly effective sound barrier

Is my home’s R-Value high enough?

The United States Department of Energy requires newly constructed homes to meet their recommended R-Value insulation standards, although these building codes were not in effect until after the mid-1970s. 

The DOE estimates that 4 in 5 homes constructed before 1980 are insufficiently insulated, leaving a large carbon footprint and owners losing large sums of money annually.

A few ways to tell if your home’s R-Value doesn’t meet industry standards:

  • Fluctuating temperatures inside the home
  • High energy bills
  • Constant adjustment of the thermostat
  • Drafts inside the home
  • Outside noises travel inside easily

What R-Value is best for garages?

To determine what R-Value is needed for your garage’s exterior walls, you must determine what size wood board was used to construct it. The typical house and garage have 2×4 wood boards, which require an R-Value range of R-13 to R-15, with a minimum recommended r-value of R-10.

The ceilings of your garage may support a finished room or an unfinished attic. If it is a finished room above your garage, you’d typically only have space for insulation of R-30. If it is an unfinished attic, you may have enough space for insulation of R-38. An R-Value above R-30 will prevent rising heat from traveling into the home.

Insulation batts near the garage walls.

Are garage doors important to insulate?

Garage items are essential to protect, and insulated doors help to do that. The majority of garage doors are steel, a material that is a heat conductor that can pull heat into the garage or remove it. This causes a fluctuation in garage temperature and higher energy consumption.

If your garage is not heated or cooled, R-6 to R-9 insulation is sufficient for regular garage uses, such as storage. For garages that are conditioned (heated or cooled), then R-9 to R-13 is adequate, though the R-Value should be as high as possible to retain the air conditioning. 

Garage door insulation can be an easy fix. You can use your original door and install your insulation or get it professionally done. Though the top-recommended insulation, polyurethane foam, will require professionals. Polyurethane (spray foam) is the best insulation option because it bonds the front and back of the door together for structural support and gets into the crevices and cracks to prevent all airflow.

If you want to DIY the installation, then there are a few things you need to know. Due to its shallow structure, a typical door can only hold insulation up to R-12. The best insulation for self-installation is vinyl-faced batts, foil-faced batts, or foil-faced rigid foam boards. They can be cut to size and placed in each panel. 

A pre-insulated door is recommended in colder climates so that the R-Value reaches at least R-14 to R-16. Pre-insulated garage doors tend to have higher R-Values due to their construction but cost a pretty penny while using the same materials of steel and polyurethane.

Can you add more insulation on top of your existing insulation?

Many articles suggest that homeowners who want to meet R-Value standards can add to their existing insulation, and it will be effective. However, the Department of Energy advises against it as dense insulation will compress the lighter, older materials and will not give you the total R-Value rating. This differs between types of insulation as well.

Blowing Blown-in insulation into a wall for soundproofing.