They can cool the attic … but at what risk to the structure and the occupants? Could radiant barriers represent a potential for harm?
Read the McDowell Owens Engineering Inc. white paper as to how “The physical and electrical properties of these materials are such that they introduce new and very serious dangers of ignition and fire.”
The link that I had used for years to the original McDowell Owens Engineering Inc. report is no longer operating; however, you can find a pdf copy of the report by clicking here.
The summary of the McDowell Owens Engineering study is, as follows:
“1. Standard installation methods for roof sheathing with integrated radiant barrier are such that the end result is an overall environment where all of the radiant barrier material and virtually everything metal on and around the roof are electrically connected.
“2. In most cases, something in that environment is connected to earth ground. If anything in the roof environment becomes electrically energized (by lightning or any other common source) there is a high probability the current will pass through the barrier material at some point on the way to earth ground.
“3. The physical and electrical properties of reflective radiant barrier materials which we tested are such that the material in a structure provides two new and unique hazards relative to fire causation.
(a) When energized by an electrical current the material readily generates temperatures sufficient to ignite MANY materials.
(b) The barrier material itself readily serves as the first ignited material.”
If you are considering radiant barriers as an energy efficiency upgrade … if you reside in a home with radiant barriers that are installed … if you are considering a recommendation by an energy auditor or other entity to install them … read this report, first.
good information. I had no idea. Thanks!
While this is the only study I have read on this issue, it was referred to me by an insurance adjuster who had written an article for other adjusters concerning litigation against radiant barrier installers to recover cash awards made to home owners who suffered damages from fire resulting from radiant barriers.
It is a blip on the radar, today … but it is has the potential to be big and those who are recommending and installing this product, today, should be aware of this potential, IMO.
Seriously? The fire was caused only by the barrier & not the incorrect electrical & possible poor barrier installation – nice try on that one. With that said, that would be a good thing to remember for our friends up north which are the only ones that should even consider installing RB that way
As for the sheathing & lightning they might want to study up on lightning as all their experiments & the one diagram are so ludicrous it isn’t even funny.
I have to agree with your comment except for “that would be a good thing to remember for our friends up north which are the only ones that should even consider installing RB that way”. Radient barriers are a waste of time and money in heating dominated climates. Even in cooling dominated climates where they often just roll the RB out over attic insulation you often see moisture problems. Better to spend time and money on a tight building envelope and better insulation . Here in Zone 5, I actively campaign against RB installs on projects I am involved with.
That being said. the drawings mean nothing. If there is a TV antena, it will have a ground wire and lightning strikes to the antenna will never see the RB. Where the RB is laminated to the sheathing there is no path to ground as the gutter down spouts do not go to ground. Besides, the lighting is not striking the RB, it has a cover of insulating roofing and sheathing. Yes the nails have a covering of shingles.
As for the lab test, it bears little resemblance to actual building. I can set up lab experiments to imply most any desired conclusion, it you allow me to ignore some of the variables. Yes, I can put an electrical load through a thin Al strip and get it to set fire to the paper underneath, or even to melt the strip. How does this relate to an actual RB install?
This is in the same category as “Radient barrier technology, like used in the NASA programs”.
No arguments from me on our friends up north not using it or it is better to air-seal & insulate – I was just trying to point out that those that do install it, need to make sure it is installed properly & there are no open / exposed circuits