Minimum Roof Insulation Thickness

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.

Minimum roof insulation thickness.

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. The minimum thickness of insulation directly over fluted steel decks shall be a minimum of one half the nominal flute width. Hitting amazing levels of 0 13w m will need 300mm of mineral wool or 180mm of rigid foam. Basically 4 of insulation is required with the only exception at roof drains.

Spray polyurethane foam has an r value of 6 6 per square inch of thickness. 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. At roof drains the 4 of insulation can taper down to 3 within the area of the drain sump. Hunter panels roofing tech topic r105 15 franklin street portland me 04101 888 746 1114 fax.

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. 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. Zone 6 requires an r 30 minimum which is 5 2 thick.

To get to an r 25 you ll need to install an average of around 4 inches of spray foam. The importance of insulation thickness r value isn t just a time measurement though. X 6 6 r value r 26 4. In ohio which uses the 2017 ohio building energy code will need to meet or exceed an r 25.

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. 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. 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.