Can I Install Radiant Barrier Under The Shingles If I Re-Roof My Home?
Can I Install Radiant Barrier When I Have a New Roof Installed?
This is a VERY common question. People often think. "Hey, they are taking off my shingles, why don't we just lay radiant barrier foil out and then put the new shingles back on top? This would be a whole lot easier than stapling the foil inside the attic." STOP - IT WON'T WORK - IN FACT, IT WILL ACTUALLY WORK AGAINST YOU!! DO NOT DO THIS, AND RUN AWAY FROM ANY ROOFER WHO TELLS YOU OTHERWISE!!
Why Not?
It gets a little tricky, but I will explain it. Radiant Heat BY DEFINITION is heat that travels as RADIATION in waves ACROSS either a VOID (air gap) or VACUUM (Think SPACE, like the heat from the Sun reaching the Earth).
Radiant Barrier works in one of two ways: Either it REFLECTS the radiant heat (think of the foil covered sunscreen in your windshield) or it works off of EMISSIVITY which is the ability NOT to emit heat in the form of radiation. (think wrapping a potato to keep it hot).
NO Air Gap = Solid
If you take radiant barrier foil and "Sandwich" it between the shingles and roof felt, you have now created one solid assembly. Aluminum is a unique element, it is BOTH reflective and very conductive. This is why we cook with aluminum cookware because CONDUCTS heat so well. Here is good illustration most people can relate to: Have you ever picked up a hot potato that it wrapped with foil? It feels Super-Hot right? Why? When your skin touches the foil it creates direct path (NO air gap) for the heat to flow Potato=>Foil=>Skin and you feel the heat.
But My Roofer Said It Will Work
Ask the roofer if they have a good lawyer? I know of several cases where the roofer "installed" a radiant barrier in this manner. I often see products (sometimes including AtticFoil) incorrectly installed in this way to try to create a radiant barrier. They had NO defense since the laws of physics and the definition of radiant heat / radiant barrier apply to a roof too. They ended up settling the case since their lawyer said they had NO defense since you can't have a radiant barrier without radiant heat and you can't have radiant heat unless there is an airspace for radaint energy to travel across.
What About a "Raised" Roof, like Tile, Metal or Raised Metal Shingles?
Yes!! NOW we are talking!! Here is complete information on Installing Radiant Barrier Under A Tile or Metal Roof If you are going to have a roof like this installed then go for it! You HAVE the necessary air gap to make it work and the results are awesome. You can install the radiant barrier foil below the raised shingles either on top or below the battens. The easiest and best way is to run the foil out over the roofing felt, tack it down and then install the battens followed by shingles or metal roofing.
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| This is an example of a tile roof over a batten system. The battens create the necessary air space to make the system work. This is the same for concrete or slate shingles. The heat radiates toward the roof deck and 97% of the radiant energy is bounced back. This is a GREAT SYSTEM. This is also the best system to use on non-vented and sealed foam closed attics. | This is a stone-coated metal shingle. This was a re-roof job. After tearing off the old shingles, the roofing contractor installed roofing felt covered by perforated radiant barrier foil. Then wood battens were installed to attach the metal shingles. |
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| Installing the radiant barrier foil under a metal roof is quick and easy. Installers just roll it out and cut it with a knife. Use a few staples to hold in place, then install battens. Be careful to work so the sun won't reflect in your face, it can be blinding. Sunglasses are highly recommended. | This roof is complete and ready to attach the shingles. Our radiant barrier is so durable, you can take it on the roof and be rough with it. it won't tear and the foil can be exposed to sun or rain for a limited time without problems. |
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| This is a close up of the space (air gap) provided by using the metal shingle. The red shaded are is the "void" below the shingle. Most tile and metal roofs also provide the required air gap. | Adding a radiant barrier to your re-roof project is a smart idea. It adds minimal labor and cost. The increased energy savings can pay for itself usually the first year. |
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| This is an example of a tile roof over a batten system. The battens create the necessary air space to make the system work. This is the same for concrete or slate shingles. The heat radiates toward the roof deck and 97% of the radiant energy is bounced back. This is a GREAT SYSTEM. This is also the best system to use on non-vented and sealed foam closed attics. | Finished standing metal seam roof with radiant barrier installed below the metal roof. Considering the expense of metal roofs, it is a SMALL additional cost to install radiant barrier during the roofing installation. |