Metal roofing systems may be more expensive initially than a conventional asphalt roof but in terms of environmental benefits, a metal roof cannot be beaten.
Metal roofing is the choice for providing energy efficiency and all that cascades from it:
- Lower energy costs
- Lower energy usage
- Less waste
Metal roofs are gaining ground as more builders are embracing the green movement. More stringent building codes and tax credits are lifting metal to the top of the list of desirable roofing materials.
Let’s talk energy efficiency
The best reason for selecting a metal roof is the potential for extreme energy efficiency. Metal roofs save energy in multiple ways:
- Solar energy emissivity and reflectivity
- Accommodation for additional insulation
- Ease of installation of rooftop fixtures for other energy saving devices
- Decreased electric lighting needs
A light-colored metal roof can save building owners up to 40% of energy expenditures. Where white or light coatings on other roofing materials lost anywhere from 25% to 40% in initial reflectance over time, a white or light-colored coating on a metal roof retained most of the initial solar reflectance. If the metal was prepainted at the manufacturer, it could retain as much as 95%.
An unpainted metal roof can even outperform conventional asphalt shingles. Solar reflectance from an unpainted metal roof typically exceeds the federal EnergyStar requirement of 60%. Depending on the color of the metal or coating, reflectance can vary from 10%-75%. Compare that to the typical asphalt shingle, which has a reflectance of 5-25% regardless of color.
Reduced heating and cooling
High reflectance and emissivity plus additional insulation result in a building that is as much as 50 to 60 degrees cooler than one with a traditional roof.
Consider also that heating and cooling consumes around 30% of all energy costs for a building. Half of that loss is due to cooled or heated air escaping the roof. The best way to keep the environment stable without increasing HVAC use is to increase the amount of insulation beneath the roofing system.
Unfortunately, increasing the amount of insulation under a conventional roof often has the effect of causing the roofing materials to deteriorate more quickly. However, a metal roof can accommodate much more additional insulation without any problems.
Reduction in electricity usage
Skylights and other rooftop devices can help increase the amount of natural daylight within a structure. To decrease electric lighting without additional effort, you can install skylights with electronic lighting controls capable of turning off unneeded electric lights.
Savings can be as much as 35% to 55% of annual lighting energy usage adding up to 11 cents to 32 cents per square foot of savings depending on climate and building type.
Newer types of skylights are available that can collect three times as much light because they can capture the sun's rays both earlier and later than flat skylights. The new top-lighting is dome-shaped with prismatic embossing that refracts light into micro-beams, which transmit more light without glare, hot spots, or UV damage.
Fewer skylights are needed, reducing the number of roof penetrations by 30% and decreasing the chances of a leak.
Not only do the domed lights reduce electric lighting costs by up to 70% when integrated with electronic light controls, but you will also achieve a return on investment within three to five years.
Cool metal roofing makes a global impact
Cool metal roofs do more than saving the individual building owner on energy costs. If more buildings and homes have metal roofs installed, global benefits will follow in the form of:
- Climate change mitigation
- Urban heat island mitigation
- Smog reduction
- Healthier public
- Grid stability and peak energy savings
If less electricity is required on a daily basis, less power can be generated. Reduced power generation results in lower CO2 emissions from power plants. A study by the Lawrence Berkeley National Laboratory found that worldwide reflective roofing could produce a global cooling effect equivalent to offsetting 24 gigatons of CO2 over the lifetimes of the roofs.
That is a savings of over $600 billion.
Urban heat island effect
Heat within a city can be two to eight degrees warmer than the surrounding area. Dark roofs absorb energy from the sun during the day and release it at night as heat, preventing the air from cooling naturally.
With higher retained temperatures daytime heating increases along with the attendant increase in energy usage. If light colored, metal roofs replaced conventional asphalt; heat would be reflected back into the atmosphere immediately. Infrared light, in particular, would be re-emitted.
The Oak Ridge National Laboratory released a three-year study on the energy efficiency and service life of metal roofing systems. Using a solar spectrum reflectometer and an emission meter, the lab demonstrated the cool metal roof provided high solar reflectivity and high emissivity, both of which mitigated the urban heat island effect.
Smog is created when air pollutants undergo a photochemical reaction. These reactions increase as the heat increases. A reduced air temperature from cool roofing can decrease the rate of smog production.
Less smog means lower ambient air temperatures, also reducing the heat island effect.
Public health benefits
How much lower could the rates of asthma and heat stroke go if there were lower air temperatures and improved air quality? The rates of both have been on the increase over the past few decades.
Peak energy reduction and grid stability
If less air conditioning is needed during the day over a wide swath of buildings and homes, then electricity use will certainly go down. Stress on the electrical grid would be reduced and the amount of energy required at peak usage times would go down as well.
The result should be fewer blackouts and brownouts. Those who pay for energy based on the time of use would see lower bills.
You have already seen how a cool roof can reduce the need for air conditioning. It follows, then, that lower energy use will help lower the ambient temperature because the heat island effect is reduced.
Lower ambient temperatures further reduce the need for air conditioning during daytime hours, saving even more energy. CO2 emissions are reduced due to lower demand for electricity-generating power plants.
It becomes a cycle of green.
Need more reasons to go with a metal roof?
How about these?
- Metal roofs are durable, lasting two to three times longer than a conventional roof. There is less cracking and breaking and more resistance to high wind and impact. Therefore less maintenance is needed.
- Metal roofs are made of 40% or more recycled materials and are, themselves, 100% recyclable. In comparison, nearly 11 million tons of asphalt shingles are dumped into a landfill annually.
- Metal roofs are sustainable. They accommodate renewable energy devices such as solar panels and solar water heaters. They can generate electricity from thermal energy without roof penetrations.
The environmental benefits of metal roofing continue to grow every day as new construction turns to steel and other metals to top commercial buildings and private homes.
It has never been better, or easier, to be green.