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TOPIC: Galvalume

ENERGY EFFICIENCY

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Would it be a waste of money to use a radiant-barrier decking (Tech-shield) under my bare galvalume standing seam roof (new construction)? Does the galvalume have any radiant-barrier properties on its own? Emmisivity values? How much heat is reflected? Etc. I would appreciate any input.
Guest User

6/8/2001
Your link to the Florida study using various roofing types only rates a "white metal" roof. Is it the color or does a metal roof in general provide a radiant barrier? I would be vary interested in the savings in energy (cooling) with all forms of metal roofing and particularly the shingle look alikes in a darker color. I also see nothing on ridge vents associated with metal roofing.
Guest User

6/10/2001
A great deal of research is ongoing concerning the efficiency of metal roofing. Florida Solar Energy Center does side-by-side tests every year comparing various types of roofing. One product they tested in 1999 was a white aluminum shake product. It performed extremely well. The following year, the same aluminum shake was tested in a brown color. It did not perform quite as well in the brown as it did the in white but it still did much better than dark standard shingles. In any roofing product, light colors and white will be the most effective at reflecting radiant heat. Metal roofing has the added benefit of staying fairly clean over time in most situations. Additionally, with the coatings used on metal roofs, fairly bright white colors are possible. However, particularly when you're looking at formed shake, shingle, and tile products, metal has an added benefit because of the airspace that is created between the metal roofing and the roof deck. This airspace will not conduct heat the way that direct contact between roofing and roof deck will. This is why the 2000 test I cited above showed good results even in a dark color. In 2001, the same laboratory is testing the same aluminum shake product using a new paint finish that has strong reflectance even in dark colors. It will be very interesting to compare this to the 1999 and 2000 results. For further energy data, contact the metal roofing manufacturer of your choice and they'll be glad to discuss data and experiences with their particular products. Todd Miller
Todd Miller
Isaiah Industries, Inc.

6/10/2001
Previous messages asked about ridge vent and radiant barriers on metal roofing. I too have those same questions in mind. Can we expect a Tech Expert's reply to those questions?
Guest User

6/12/2001
These are good questions. Sorry I got carried away and forgot to address them earlier! There are lots of studies showing the effectiveness of radiant barriers beneath standard roofing shingles. I am not aware of any specific studies into the effectiveness of radiant barriers with metal roofing but I can assume that they would further enhance the energy efficiency of the roofing. After all, they are just "more of a good thing" in that they behave somewhat similar to how metal roofing behaves. And, whereas there are sometimes concerns with the possible negative effect that radiant barriers can have on standard shingles, they will not affect the life of metal roofing. There is an MRA member who manufactures radiant barriers -- Environmentally Safe Products. Their website is www.low-e.com As for ridge vents ... good ventilation is important for all structures. Proper ventilation can help avoid excessive moisture and heat build-up in attics. It can also help avoid wintertime problems with ice and snow. Ridge vents are a very effective venting method, particularly when combined with soffit vents. The soffit vents serve as the intake and then air and moisture are exhausted out through the ridge vent. Most commonly available ridge vent systems can be used with most metal roofs. Some metal roofing manufacturers also manufacture matching ridge vent systems for use with their roofing products. From a personal standpoint, I would probably prefer to see a ridge vent system made from the same metal as the roof. There are several ridge vent systems available that are produced from polymers. However, I'd be a bit concerned that they wouldn't last as long as the roofing system itself. I hope that this answers your questions. Thanks for your interest! Todd Miller
Todd Miller
Isaiah Industries, Inc.

6/13/2001