Roof Rafter Depth For Rigid Foam Insulation

At 5 even hfo blown closed cell foam is only r35 ish.

Roof rafter depth for rigid foam insulation.

It provides an r value of 4 per inch of thickness and is the cheapest type of foam board insulation. Uneven or sloppy application however can make the insulation ineffective and unsealed open cell insulation can absorb moisture causing the roof to rot or leak. This foam board insulation is the rigid pink or blue panels that can be found at home centers in many different thicknesses. The first issue is with regard to how to insulate the sloped portion of the roof.

There will also be kooltherm k7 pitched roof board between the rafters image credit. The current status is that we have 2x6 roof rafters actual 2x6 s the house was built in 1915 that are 20 o c. So we need to do two things. Hitting amazing levels of 0 13w m will need 300mm of mineral wool or 180mm of rigid foam.

That would mean increasing the rafter depth to total of 9 5. Convenience polyurethane or polystyrene spray foams can provide thorough coverage to roof rafters and attic walls in much less time than is needed for other materials. 1 improve the structure of the roof and 2 allow more space for insulation. For retrofit projects kingspan kooltherm k14 insulated plasterboard goes under the rafters.

Select rigid foam insulation boards that are at least 1 2 inch less in thickness than the rafter space is deep if you plan to finish the attic as living space. 2 measure and cut the foam boards as. Eps is used under roofing over foundation walls and beneath siding. But a 2x6 rafter with a 1 5 vent space would give you the ability to put 4 of rigid insulation r 26 in that space which was not filled.

But at 4 would be sufficient dew point control to install r23 rock wool 5 5 to the interior side and you d be more like code minimum. 2 would be to create the baffle in the 1st place. Rigid polyisocyanurate pir foam insulation boards from celotex are among the most thermally efficient commonly available insulation materials on the market. Under a slate roof.