Metal Roofs

This post began as an article about water conservation and water catchment systems. I still intend to write that post later, but in the process of researching water catchment systems I got sidetracked. Like any living system, a house is hard to separate into its parts. Once you start looking into one part, you can’t help but see the interconnections.

So, this post isn’t about water catchment systems, in fact it’s not even about water. This post is about roofs. Specifically, metal roofs and why I am a convert to this type of roofing.

In my research about the best roofs for water catchment systems, metal roofs kept showing up as the superior choice. That’s one reason why I became convinced that metal roofs are the preferred material . But it’s not even the best reason.

Water conservation can wait. You are going to want to know about metal roofs first.

Here are what I consider to be the reasons everyone should want a metal roof:

• Metal Roofs are Cooler (as in temperature, but they’re pretty hip as well)

The Department of Energy reports that buildings use 2/3 of all the electricity and 1/3 of all primary energy consumed in the country. The type of roofing on a structure can significantly impact the energy use of the building in terms of cooling and heating energy requirements. Reflective roofing can directly save up to 40% in energy costs. Cool roofs are those with radiative properties that reduce the surface temperature, minimize the amount of heat transferred into the living space, and reduce the heat released from the surface to the ambient air. The Florida Solar Energy Center (FSEC), after studying the cooling energy of identical size, unoccupied homes, concluded that a white painted metal roof could save the typical Florida homeowner 23% annually in their cooling energy costs, compared to a dark gray asphalt shingle roof.

In terms of style, the choices in metal roofing go beyond just white paint. The family of metal roofing contains unpainted natural metal surfaces, prepainted metal surfaces, and granular-coated metal surfaces. A recent technological improvement in the use of infrared reflective pigments allows for more solar radiation to be reflected even with darker colors. This advance is allowing for popular colors other than white to be considered cool roofing.

• Metal Roofs are Eligible for Incentives and Rebates

The 2009 Stimulus Package provides substantial tax credits to homeowners who make energy efficient updates to their home. One of the best ways to qualify for the credit is installation of a painted or coated Energy Star labeled metal roof. Homeowners installing qualified roofs in 2009 and 2010 may be eligible for a tax credit worth up to 30% of the materials cost up to $1500 per home.

• Metal Roofs Ease Urban Heat

Urban areas are prevalent with dark building materials, dark pavements and dark roofs that absorb solar radiation and become hot. In addition, the lower amount of vegetation in the urban areas, compared with the surrounding suburban areas, contributes to the warming. Because of this, urban temperatures are 6-12 degrees higher than the surrounding suburbs and rural areas. The higher air temperature increases smog and requires buildings to use more energy to keep cool. The Lawrence Berkeley National Laboratory conducted a computer simulation estimating the impact of reflectance and emittance on heating and cooling energy consumption and concluded that $750 million could be saved annually by the use of light-colored reflective roofs.

• Metal Roofs are Sustainable

In addition to its energy efficiency benefits, metal roofs are also incredibly environmentally friendly. Metal roofs are extremely durable over time. Metal roofing withstands harsh weather including high winds, hail, ice and snow loads. It can also withstand the wet/dry cycles that often destroy other materials. The durability of prepainted metal roofing is important since over time conventional roofs can become soiled by air pollutants, biological growth, and general degradation. These factors impact the reflectance values and therefore the energy costs of a building. Prepainted metal was found to retain almost 95% of its initial solar reflectance over three years of exposure. As a comparison, some membrane roofing products and white coatings showed a 40% and 25% drop in reflectance, respectively, over the same exposure period. Given the energy savings of metal roofs, and the projected life span of 30-50 years, metal roofs more than pay for themselves.

Metal roofs typically have a minimum of 25% recycled material and can be completely recycled when they are removed from a building. Compare that to typical roofing material that is often classified as hazardous waste when it is removed and routinely ends up in landfills.

The weight of a metal roof can be as little as 1/8 that of conventional roofing shingles. The lower weight, but higher strength, of a metal roof means that metal roofing can be installed over old roofing material without tear off and disposal. However, in my personal opinion, while it may be cost effective to install the metal roof over old roofing, I find it best just to start new and dispose of the old roof first.

• Metal Roofs are Cost Effective

Metal roofing material comes in a variety of styles and colors and therefore the price can vary anywhere from $1.50-$5.00 per linear foot and can be even higher for specialty systems. For example, there are metal panels, metal shingles, metal slate, metal shake, and metal tile roofing. I should make the caveat that, like other green home improvements, initially the total cost of material for a metal roof may be more than a shingle roof. However in my experience, installation is faster on a metal roof than a shingle roof and therefore labor costs are less expensive. Additionally, considering how long metal roofs last, the higher initial cost of the metal roof is more than made up for over time.

• Metal Roofs are Excellent for Water Catchment Systems

In terms of water catchment systems, metal roofs have the advantage as they have a slicker surface, so they don’t collect as much debris and dirt to be filtered. With other systems, you have to worry about grit, bird droppings, pathogens, toxins leached from the roof materials, and bacterial growth. In fact, a study by Oak Ridge National Laboratory found that metal roofing products resisted the growth of biomass which can lead to mold or fungus.

The only warning with metal roof catchment systems is to be careful of copper roofs. Copper is toxic and low pH rainwater will erode it a bit. If you are going to use the water for drinking, you should test it to make sure the copper level isn’t too high.

Given these benefits of metal roofing, I think you can see how I could get sidetracked. There are green technologies out there that apply new and complex solutions to difficult problems. However, I enjoy the beauty of a simple, traditional solution to creating a more environmentally friendly, comfortable home.

References

Kriner, S. “Architects Turn to Cool Metal Roofing in North America.” International Conference on Building Envelope Systems and Technologies

Oak Ridge National Laboratory. “Cool Metal Roofing: The Energy-Efficient Choice.” Buildings Technology Center

www.metalroofing.com/v2/content/guide/costs/energy-tax-incentive.cfm

Schneider, Jim. “Catch the Rain: Metal Roofs Provide an Ideal Platform for Rainwater Capture.” Metalmag, February 2010

www.bestbuymetals.com