A highly reflective roof can make your home more comfortable, and save you thousands of dollars in air conditioning over its lifetime; new metal white roofing is one of the best choices to provide it.
New metal roofing materials - namely anodized aluminum and galvanized steel products - are much better than older bare metal products or common shingle and tile roofing materials at providing reflectivity.
Light-colored metal roofing has an important advantage over other traditional roofing materials, in hot climates: it cools faster at night…
There are very few roofing materials able to match with new metal products in terms of reflectivity (see, for a technical review: enduse.lbl.gov) or durability.
Light colored metal roofing is still the best choice for energy efficiency; new darker colors, with special treatments, have good “reflectance” but white and light colors are better.
Pros and cons
Reflective roofing materials should both reflect and release solar heat.
The SRI index (Solar Reflectance Index) provides a rating system on a 0 to 100 scale (the higher the SRI the best).
Dark asphalt shingles SRI: 1-5%;
White asphalt shingles SRI: 20-25%;
White metal roofs SRI: 70-80%;
White clay tile SRI: 70%.
Metal roofing products can be made from recycled materials, and you should prefer them.
They are indistinguishable from other metal roofs in their reflectivity (around 80%, in a 0-100% scale) or in their durability and low maintenance.
Modern metal roofs are very strong and durable; they can withstand severe winds, and other extreme weather conditions. They are among the most durable and strong types of roofs on the market. They can now be shaped to look like common asphalt shingles and wooden shakes.
Metal roofs will not increase the likelihood of lightning striking, and issues as higher noise or rust and denting are myths or problems that can be solved by today’s technology. Rusting – a problem that still affects the owners of older metal roofs – is no longer a problem with new galvanized and anodized products.
The only "problem" with metal roofing is that it is a lot more expensive than other traditional options. Metal roof prices vary a lot, but expect prices between $350 and $1,000 per 100 square feet, that is, often twice the price of common asphalt shingle systems...
Manufacturers and brands
The Energy Star list of energy-efficient roofing products is a good starting point to look for manufacturers. You can take a look at it, here (PDF).
To find a installer, in North America, you may use the NRCA (National Roofing Contractors Association) search tool.