Minimum Roof Insulation Thickness

At roof drains the 4 of insulation can taper down to 3 within the area of the drain sump.

Minimum roof insulation thickness.

To get to an r 25 you ll need to install an average of around 4 inches of spray foam. You can see from the table that the recommended thickness of loft insulation is currently 270mm. 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. 877 775 1769 hunterpanels com 0716.

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. 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. The minimum thickness of insulation directly over fluted steel decks shall be a minimum of one half the nominal flute width.

Spray polyurethane foam has an r value of 6 6 per square inch of thickness. 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. Basement walls require a minimum of either r 10 continuous or r 13 batted insulation. 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 importance of insulation thickness r value isn t just a time measurement though. 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. X 6 6 r value r 26 4. Zone 6 requires an r 30 minimum which is 5 2 thick.

Hitting amazing levels of 0 13w m will need 300mm of mineral wool or 180mm of rigid foam. Hunter panels roofing tech topic r105 15 franklin street portland me 04101 888 746 1114 fax. It takes into account the size of the sample and the overall change of temperature over time so that you can compare thermal conductivity of materials tested with plates of different temperatures or even that were tested by other methods.