What insulation has the highest R-value?

In today’s blog post, we will answer the following question: What insulation has the highest R-value? We will explain what an R-value is and how to choose the best type of insulation for your RV. 

What insulation has the highest R-value?

The insulation type with the highest R-value per inch is the rigid foam panels. In its rigid version, the polyurethane takes the form of rather light panels (density of 70 lbs / ft3). They are nevertheless very resistant and can be used for all cases, whether for interior insulation or exterior insulation. 

Other advantages of rigid foam panels are:

  • Thickness: Polyurethane panels have a thickness ranging from 1 to 8 inches depending on the product. A small thickness of rigid foam panels will suffice to achieve good insulation.
  • Comfort: Insulating your RV with rigid foam panels can significantly reduce the summer heat by including the material supporting the thermal inertia of the vehicle.
  • Price: Rigid foam panels remain fairly inexpensive because it is quick to install (no cutting) and requires little labour (one person is enough). It takes between 10 and 25 $ per sq ft depending on the thickness chosen.
  • High R-value: The more efficient the insulation and the greater the thickness, the more the RV will be insulated from both heat and cold.

Note: An R coefficient equal to 7 represents good insulation. Consider the thermal material, ecological insulation, thermal conductivity, minimum thickness in inches to obtain the correct insulation R-value. It is preferable to insulate your RV as much as possible and as soon as possible!

What does the R-value mean?

The coefficient of thermal resistance (noted R) is an indicator of the ability of an insulating material to resist temperature differences due to heat or cold. The higher the value of R, the higher the material’s thermal insulation capabilities.

The index is expressed in sq ft K / W (Kelvin per Watt). The R coefficients are given for an equal thickness. Thermal resistance R is assessed with another key element, thermal conductivity: the lambda whose symbol is “λ”. Lambda determines the ability of an insulating material to conduct heat. An insulating material must have the lowest possible lambda.

The purpose of insulation is to slow down the heat coming from heating or coming from outside. The phase shift is the time it takes for heat to pass through insulation, the higher the number of hours, the better the performance.

Everyone says that the natural resources of the environment are not inexhaustible, all energies are limited in a finite world. It is therefore imperative to use healthy and natural materials which are generally used in the construction of RVs. Some natural materials from environmental sources that produce very little waste, do not cause pollution during their manufacture and recycling.

What are the best insulators for RVS?

The higher the R-value of an insulator, the more insulating the material. However, we should not focus on this single criterion, because other factors intervene for the comfort of an RV. The material should ideally be:

  • healthy (no petrochemicals),
  • breathable (it must allow water vapour to pass through),
  • sound-absorbing,
  • well implemented (a poorly laid or hasty material can lose 80% of its intrinsic qualities),
  • In addition, safety rules must be observed when applying an insulator.

There are many types of insulation materials to choose from. Here are our top three choices:

  • Fibreglass: You may choose to use fibreglass if you live in a particularly humid part of the country, as fibreglass is naturally waterproof. Plus, fibreglass is corrosion resistant and won’t catch fire or break down easily. This method of insulation can be expensive compared to other products listed but will stand the test of time.
  • Styrofoam Beads: Styrofoam beads are installed using a blower, which may need to be rented from your local hardware store. These beads are an excellent method of insulation because they are resistant to moisture. However, their R-value and thermal resistance are lower than that of fibreglass. Therefore, this material should be reserved for less severe cases.
  • Cellulose: Like rigid foam panels, you will need a machine to install cellulose-based insulation. Be aware, however, that this method of insulation will put more strain on the walls and ceiling of your mobile home than others. Also, this material absorbs water easily, so cellulose should not be used if you live in a humid climate.

How to choose the best insulation type for an RV?

To compare thermal insulating materials with one another and choose the best one, all you have to do is check 4 performance criteria on the specifications of each insulation product:

  1. Thermal resistance: To choose an insulation or insulation product, just read the thermal resistance R which appears on the product label. The higher the number behind the R, the more insulating the product. The greater the thickness of an insulating material and the lower its coefficient of conductivity (lambda), the higher its thermal resistance will be.
  1. Thermal conductivity: Lambda thermal conductivity (λ) is the amount of heat W / m.K that can pass through a material in a given time. The lower this value (λ), the more the material, for equal thickness, will be insulating. Insulating materials have λ <0.060 W / mK. N.B. Some manufacturers calculate the lambda of their insulation with an air temperature of 10 ° which is false.

The lower the thermal conductivity, the higher the R coefficient and the more insulating and efficient the product.

  1. Airflow: The long lawsuit between the powerful union of mineral wool manufacturers against a small manufacturer of thin reflective products which claimed that its aluminized product was equivalent to 10 cm of glass wool produced an unexpected result.
  2. Reaction to fire: In the US, the classification is made up of six categories which defined the reaction to fire of materials:
  • “incombustible”
  • “non-flammable”
  • “hardly flammable”
  • “moderately flammable”
  • “easily flammable”
  • “very easily flammable”

A material is classified incombustible if it meets the following conditions:

  •  no effective ignition on radiation test.
  •  it meets the conditions of the classification for the electric burner.
  •  its superior calorific value is less than or equal to 2.5 MJ / kg (600 Kcal/kg).

Note: Ecological insulating materials offer a major benefit over mineral or synthetic insulations: their permeability to water vapour allows the walls to remain breathable while avoiding the risk of condensation by ensuring good airtightness.

The materials offering the most permeability are products derived from wood, wood wool, vegetable and animal wool, terracotta, lime, plaster, cellulose wadding, etc.


All insulation materials have their own drawbacks and qualities. There are many advantages of insulating your RV and it is not a complicated process at all. It can be done quickly and with relatively low funds, but it will bring you so much comfort no matter the season. 

Do you have any thoughts or comments about this subject? Please let us know!

FAQ on What insulation has the highest R-value?

How to thermally insulate a caravan?

To thermally insulate a caravan you can use an asphalt blanket, aluminium adhesive felt, EVA thermal insulation or aluminized etalon. Coating the interior of the vehicle with these characteristics is what creates the insulating layer, helping to prevent heat from the exterior from reaching the interior of the vehicle.

How is the insulating membrane placed?

The role of insulation should be extended towards the highest part of the ceiling. Once the roll reaches the highest level of the ceiling, it must be attached to the structure. Once the insulation is fixed on the top of the roof, it should be aligned until it is parallel with the braces. 

How can I insulate a van?

The best option to insulate the van: Kaiflex or Armaflex type synthetic rubber elastomeric foam. The best insulating material is elastomeric foam based on synthetic rubber with a closed-cell structure. The best-known brands are Kaiflex or Armaflex.

How much does it cost to insulate an RV?

The costs to insulate an RV will greatly depend on the area you must insulate. On average, you need to put aside between $5000 to $7000.