Minimum Roof Insulation Thickness

The importance of insulation thickness r value isn t just a time measurement though.

Minimum roof insulation thickness.

X 6 6 r value r 26 4. Basically 4 of insulation is required with the only exception at roof drains. This exception will allow the minimum thickness to be 4 2 at the low point or 5 2 4 away from the drain on a per foot tapered system. To get to an r 25 you ll need to install an average of around 4 inches of spray foam.

Zone 6 requires an r 30 minimum which is 5 2 thick. Basement walls require a minimum of either r 10 continuous or r 13 batted insulation. When builders ask for advice about installing rigid foam on the exterior side of a wall i usually refer them to one of my articles calculating the minimum thickness of rigid foam sheathing the article explains that the r value of the rigid foam layer needs to be high enough to keep the osb or plywood sheathing above the dew point during the winter. The minimum thickness of insulation directly over fluted steel decks shall be a minimum of one half the nominal flute width.

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. The amount of insulation has not changed over the last 14 years though so it seems an increase in the recommended amount will most likely come shortly. Hitting amazing levels of 0 13w m will need 300mm of mineral wool or 180mm of rigid foam. 877 775 1769 hunterpanels com 0716.

You can see from the table that the recommended thickness of loft insulation is currently 270mm. The minimum roof insulation is a significant change from the average roof insulation we are familiar with using. In ohio which uses the 2017 ohio building energy code will need to meet or exceed an r 25. Spray polyurethane foam has an r value of 6 6 per square inch of thickness.

Achieving a u value of 0 20w m meaning your roof will be better insulated than your walls will need 120mm thickness of rigid foam or 200mm of mineral wool or natural insulation. Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces. If structural sheathing covers 40 or less of the exterior continuous insulation r value shall be permitted to be reduced by no more than r 3 in the locations where structural sheathing is used to maintain a consistent total sheathing thickness.