The most popular solution is adding some insulation and retrofitting a new roof membrane over the top. This is were roof insulation Flute Fillers play an important role. Not only do they add R-value to the system but they can transition a flat surface for a new roof retrofit system. I typically see flute filler level with the top of the ribs/seams and one additional layer on top of that smoothly bridging the top of the ribs/seams. The question is can this system be improved upon?
The one area of thermal weakness in this system is where the original metal roof has seams (connection point of the two pieces of metal roof) that allow heat loss at those points. By installing only one layer of insulation over these seams, it allows for the potential of thermal loss at these junctures were the insulation joints meet these metal roof seams. This thermal loss could cause condensation and stress the membrane disproportionately causing future issues.
Some may say, there is insulation under the metal roof system already, those joints don't leak heat. Really? Take an infrared camera and scan that metal roof and look at the seams, you might be surprised what you find.
There are two solutions to fix this potential problem with retrofitting over a metal roof. The first solution is to add another layer of insulation and offset the joints. The second solution is to use Plymouth Foams RetroDeck™ with a cover board. This system has a built in seam offset. No roofing system is perfect, but eliminating as many potential problems can help a roof system last longer creating better value for our customers.