Insulation Thickness Calculator: Calculate How Thick Insulation Need To Be

Want to know how thick your insulation needs to be to achieve the desired R-value? Given below is a simple insulation thickness calculator that will let you input the desired R-value and select an insulation material. The calculator will display thick the selected insulation needs to be to achieve the required R-value.

How to use this insulation thickness calculator?

You need to know only two things to decide the insulation thickness. One is the R-value the insulation needs to achive. The other is the type of insulation you are using. The thickness required to achieve an R-value varies with the type of insulation material. Given in this calculator are two fields, the first one is to enter the R-value you expect to achieve. The second field has a drop-down that lets you choose the type of insulation. Once you enter these two parameters and press the calculation button, this calculator will show you how thick that particular insulation needs to be to achieve the heat resistance (R-value) you entered.

Insulation Thickness

Desired R-Value

Insulation Material

Given below are the R-values per inch used for the different insulation materials listed in the above calculator;

  • Fiberglass batt- 3.64
  • Fiberglass loose fill (blown in) – 3
  • Closed cell spray foam – 6
  • Open cell spray foam – 3.6
  • Foam board insulation – 5
  • Cellulose loose-fill (blown in) – 3.4
  • Rockwool batt – 3.6
  • Rockwool loose-fill (blown in) – 3

I will be adding more materials to this list soon. If you see the calculator missing any insulation material on its list, do let me know.

Charles John

A novice DIYer who learns about home ventilation. I am a mechanical engineer and have a basic knowledge of HVAC systems but I learn continuously to make myself the best blogger in that space.

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