Check out Chris Edwards at www.GreenLows.com installing Radiant Barrier Foil from Attic Foil. This video really shows how uncomplicated installing radiant barrier can be. As I mention in the video, the key is NOT to over-think the installation process.
In this video he demonstrates the Open-Ridge Method of installing radiant barrier. This is an excellent method for warmer climates and especially for homes that have ductwork in the attic.
Think of radiant barrier as shade and you are trying to protect your insulation (and the ductwork) from absorbing radiant heat coming off the roof and getting warmer. Simply staple up the radiant barrier and leave an air path for attic ventilation to do its thing.
Attic Ventilation is simple: Create a path for air to come in the bottom of the attic and out the top off the attic. If you install the foil in a way that does not BLOCK this path, you have it correctly installed.
Installing radiant barrier is a great Bang-For-The-Buck DIY project. Now is the best time to install radiant barrier while the attic is nice and cool. You will really appreciate it when the scorching heat comes back next Summer.
Looking for more videos on this topic? Check out my posts below.
radiant barrier
it seems that a radiant barrier would work best being installed on the attic rafters and above or outside of the insulation. I’m being told by an installer of a radiant barrier that they can install it inside my insulation for my attic rennovation where I am adding conditioned living space from the knee-wall up to about nine feet where the cathederal ceiling will flatten out, and that the barrier will still perform just as well. The knee-walls, side walls and cathederal ceiling will have R-30 insulation (with an inch of a vent chute installed between the rafters right under the roof), the flat ceiling and remaining unconditioned crawl-space floor will have R38 insulation. The framing and most insulation is already complete. Does it make sense to install the radiant barrier inside the insulation before putting up the sheet rock or is it too late to install the radiant barrier without pulling everything back down?
Fred,
It sounds like what you are describing would result in the radiant barrier being sandwiched between the insulation and the sheet rock, is that correct? If so, then NO, you cannot do this. You can NOT sandwich the foil between other layers (i.e. foil between insulation and sheet rock); there must be an air space on at least one side of the foil (preferably the side facing the heat source) in order for it to work. No air space means no radiant heat and no radiant heat means the foil is not acting as a radiant barrier; in fact, doing the install as you suggested will work against you!
In order for this to work there MUST be an air gap on at least one side of the foil. Typically in your case the install method would be a Cathedral Ceiling Install Method for radiant barrier, which means yes, you would need to pull down the insulation from the wall cavities and start over. In some cases, to save the trouble, customers do put the foil over the insulation and then they add furring strips (wood batts) on top and across the foil to create the airspace before adding the sheetrock; while not ideal, this does work.