Roof Rafter Depth For Ridged Foam Insulation

For the same reason insulation shouldn t touch the roof s underside.

Roof rafter depth for ridged foam insulation.

At 5 even hfo blown closed cell foam is only r35 ish. 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. The roof deck can be plywood metal concrete or wood planks. 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.

Rigid foam insulation installation prepare roof deck. Even small gaps can allow the passage of. Think of the same example of a wall and attaching drywall with the tons of screws. Staple plastic or foam baffles to the roof sheathing near the eaves to keep the material away.

That would mean increasing the rafter depth to total of 9 5. If you use open cell spray foam on your roof rafters you should cover the finished application with a paint or sealant that retards water vapor. Code specifies the minimum r value of the rigid foam layer. Rigid foam on roof sheathing with air permeable insulation between the rafters.

It provides an r value of 4 per inch of thickness and is the cheapest type of foam board insulation. In this case the rigid foam can be thinner than when it s used alone. The first step with roof installation is to prepare the roof deck by getting rid of all dirt dust and contaminants. Rigid foam also can be installed above the roof sheathing in tandem with air permeable insulation between 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. Products provide superior insulating properties. If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of the tiles or slates with an 80mm board running across the rafters. The bottom layer of a single ply membrane roofing system is the roof deck or substrate.

Foamular extruded polystyrene xps rigid foam insulation offers foamular extruded polystyrene xps rigid foam insulation offers a comprehensive line of products choose the strength you need from 15 to 60 psi and exceptional moisture resistance. 2 would be to create the baffle in the 1st place. With a warm roof the usual process is to split the insulation into two layers. The 4 of rigid foam under the rafters at least give you r26.

If they are full dimension 2x6 that s just 3 5 if milled 2x6 rare in 1900 it would be 4. Eps is used under roofing over foundation walls and beneath siding. This foam board insulation is the rigid pink or blue panels that can be found at home centers in many different thicknesses.