Since the wood framing members have a thermal resistance r value roughly equal to only one quarter the r value of typical insulation products the overall r value of the wall is calculated at.
Typical wall insulation r value.
For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3.
Insulation level are specified by r value.
These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation.
Most rv manufacturers use a dense polyfoam block foam insulation that ranges between r 5 to r 7 in their rv sidewalls.
Does not consider internal convection effects.
Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value.
See the department of energy s doe ranges for recommended levels of insulation below.
Recommended home insulation r values.
Air gap or air film 3 4 air space insulating properties.
All of us would love to have r 25 values on our rvs but the technology isn t there yet.
The higher the r value the better the thermal performance of the insulation.
The r value of air is r 1 while a thick layer of densely packed fiberglass can have an r value of r 25.
Does not consider presence absence of reflective barriers.
The table below shows what levels of insulation are cost effective for different climates and.