Parameters:
(1) recommended R-value (insulation resistance
(2) R-value for current insulation
(3) R-value for insulating material in R-value per inch
(4) area to be covered in square feet
(5) density of insulation material in pounds per cubic foot
R values in the USA are expressed in (degree F)•(foot square)•h / Btu.
SIU values for R-value is °K•(square meter)/W. 1 °K•(square meter)/W = 5.67 (degree F)•(foot square)•h / Btu
The recommended R-value depends on
(1) the severity of winter weather for the area of the country (usually based on heating degree days or HDD, with thicker insulation required for higher HDD). For example, a building in the subtropics (HDD 200) may require R-19 while one in the Northern USA (HDD 8000) may require R-49.
(2) the part of the building being insulated
supplemental insulation in R-values =
= (recommended R-value) - (current R-value)
thickness of insulation required in inches =
= (needed R value) / (R value per inch for the insulation material)
volume in cubic feet of insulation required =
= (area to be covered in square feet) * (thickness in inches) / 12
weight of the insulation =
= (volume in cubic feet) * (density in lbs per cubic foot)
While insulation is usually fairly light, its weight will add to other loads, especially when evaluating a roof.
