Evaluating the R-value of Insulation Previously Installed in Existing Homes

Calculator for determining the R-value of your existing insulation:


Thickness (inches)
Insulation type R-value per inch of thickness


R-value of your existing insulation:

Calculator for determining how much insulation you need to add:

Recommended R-value
Existing insulation R-value


R-value needed:

Calculator for determining the approximate thickness you need to add:

R-value needed
R-value per inch


Approximate thickness needed:

Insulation type R-value per inch of thickness are listed below:
Fiberglass batt or blanket (3.2 inches)
High performance fiberglass batt or blanket (3.8 inches)
Loose-fill fiberglass (2.5 inches)
Loose-fill rock wool (2.8 inches)
Loose-fill cellulose (3.5 inches)
Perlite or vermiculite (2.7 inches)
Expanded polystyrene board (3.8 inches)
Extruded polystyrene board (4.8 inches)
Polyisocyanurate board, unfaced (5.8 inches)
Polyisocyanurate board, foil-faced (7 inches)
Spray polyurethane foam (5.9 inches)

Check out the information on the product insulation packaging to find out the actual thickness for any insulation for new buildings.

For new homes check out this calculator:
Insulation calculator for existing houses

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?	Questions & Answers

Resolved questions:

» Is the spray foam insulation good for very dry climates? and how does the house react to it as the house needs to breath?

» Have a 1" gap between my gas fireplace insert and stone fireplace wall due to irregular stones. heat flows up from the gap warming a painting four feet above. what's the best type of insulation for this situation? thanks

» I have a detached garage. it has 2x4 walls, and i insulated with r-15. i plan on heating this in the future. my question-- do i need to put up a vapor barrier? menards salesman says he wouldn't, this way the walls can breath.

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