keeping the heat inside below a cathedral ceiling
This method is best for primarily cold climates.
In colder climates people are looking to help keep a room warm; if the room has a cathedral ceiling, chances are it is losing heat through that ceiling. The best way to combat against this is to use a combination of regular insulation and a radiant barrier, like AtticFoil®.
Remember, when the goal is heat retention, placing the foil closest to the inside of the home will yield the best case results. Again, you MUST have an air gap on at least one side of the foil, regardless of the type of insulation you are using.
Typically your layers will go as follows, from the roof down: Roof deck, traditional insulation, radiant barrier foil insulation, air gap (created with wood battens or foam strips), and finally, sheetrock/drywall.
Adding Traditional Insulation
If you are going to add insulation to the assembly, that is going to be the first step. If your area is non-conditioned, please see the notes below. Otherwise, you will add your insulation first, against the roof deck. You can use traditional insulation, foam board, or a combination of both. You can also use spray foam.
Typically an R-19 will fit in the rafter bay.
If you go with foam board on top, you might have to compress it a little to make it fit. Remember you’ll need to be able to see the rafters since that is what you will staple the foil to.
Adding the Radiant Barrier Foil
Now run the AtticFoil® Radiant Barrier across the rafter bays (it doesn’t matter if you install the foil horizontally or vertically) and staple the foil to the rafters to secure it in place. For vertical installs, try the 26″ wide AtticFoil® for trusses that are 24″ OC.
Now you have the following layers in the assembly: (coming from the top, down):
- roof deck
- radiant barrier foil
Continue on all the rafter bays until you are finished.
Then, use some air conditioning tape and tape the seams where the foil is overlapped.
Once you finish sealing the seams, you’re ready to install your wooden strips to create the air gap.
Creating the Air Gap
Since there is no such thing as radiant heat without an air gap, it’s time to create an air gap in the assembly so the foil will work to retain the heat in the room below.
The simple way to do this is to take wooden battens (1×2 sized works well) and attach them horizontally across the rafter bays.
This will secure the foil to the assembly, but more importantly, it will create an air gap where radiant heat can exist.
Once you have all the battens in place you will finish the assembly by installing the drywall over the battens.
The foil will have about a 1 inch gap between the drywall and itself, allowing it to reflect any radiant heat coming in back toward the living space, making the room more comfortable in colder months.
If you have a non conditioned space (meaning you are not heating and cooling the space) you are finishing out with drywall, you do not have to add traditional insulation. In this case, the installation becomes very simple.
Cut a sheet of radiant barrier to the proper length of the area you are working on.
Start at the bottom and work your way up. Run the foil across the rafters horizontally and secure the foil to the rafters with 3 to 4 staples per rafter. Continue this pattern until you have covered the entire assembly from bottom to top, making sure each run of foil overlaps the previous run by at least 2 inches.
Once the wall is completely covered with the foil, simply attach the drywall/sheet rock/ceiling over the foil.
The foil is able to work in this set up because you have about 6 inches from the deck to the end of the rafter of air space. It is in this space that the radiant heat will meet the foil and then be reflected back towards the roof.