Foam board insulation is easy to use and a great DIY way to add some insulation. It comes in standard-size 4×8 sheets and smaller sizes, in thicknesses from 1/4-in. to two inches. Some types of ...
Its R-value averages R-4.3 per inch. With its relatively large air pockets ... phenolic boards have the highest R-value of any insulation type, scoring an impressive R-8. The hard foam sheets are ...