Foil faced iso board can be cost effective insulation for finished attics and cathedral ceilings.
Ceiling roof insulation foam.
Dow froth pak 620 sealant foam insulation kit.
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Install it anywhere from the roof to the foundation.
You can even place it under the foundation slab.
If you decided to use a rigid foam board to help insulate your cathedral ceiling you would install the board on top of the roof sheathing and underneath the plywood at the top of the roof.
In most cases however insulation will not help prevent moisture problems.
Rigid foam insulation also known as insulating boards provide high r values.
Foam board insulation would be a more economical especially if you are supplying the labor see photo.
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.
Even though your attic is large this makes sense because you don t want to install your ducts or hvac equipment outdoors.
Technically known as spray polyurethane foam or spf spray foam is most commonly applied in the space between attic rafters.
Rigid insulation is one of the best tools to reduce your energy costs.
It comes in standard size 4 8 sheets and smaller sizes in many different thicknesses from 1 4 inch to 2 inches.
Spray foam is a very expensive option however.
Rigid foam board installation in the case of a cathedral ceiling involves installing three different layers that are each 1 5 inches thick according to the procedure discussed in this article appearing in fine homebuilding.
A very energy efficient enclosure results.
Some types of thicker foam board insulation are available but they may need to be special ordered.
It can act as an air and moisture barrier in addition to providing very high r value.
You can install spray foam on the underside of the roof sheathing to create an unvented conditioned attic.
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.
Foam board insulation is easy to use and is a great diy way to add some insulation.
Looking upward through the open ceiling if the exterior wall and roof deck assemblies both contain spray foam then a continuous insulation and airtight layer is established from the base of the walls to the peak of the roof.