While green roofs, are becoming are becoming more common as veritable ecosystems, or sky gardens, the use of cool roofs which reflect 80% of solar energy back into the sky could be even more effective in reducing emissions.
Green roofs may support a simple carpet of self-sufficient groundcovers such as sedum or full-fledged gardens, parks, or farms. The soil and vegetation work as green heat-insulation, mediating building temperatures all year round: cooler in summer, warmer in winter. Because the electricity needed for heater and air-conditioner is reduced, greenhouse gas emissions and costs are curbed.
Cool roofs end with similar results in different ways. When solar energy hits a conventional roof on a 99° F in summertime, only 5 % of the solar energy is reflected back into the sky. The rest remains heating the building. A cool roof, in contrast, can reflect up to 80 % of the solar energy back into space, reducing the heat taken on by buildings and the overall heat absorbed by the cities (Drawdown).
Research undertaken by Drawdown, a project connecting researchers, scientists, and graduate students to present climate solutions, the global green roofs and cool roofs market was 42.5 billion square meters in 2014. This number will double to 85.7 billion by 2050.
By expanding the use of green roofs to cover 30 percent of roof space by 2050 and cool roofs to cover 60 percent of the building roofs, some 407 billion square feet of efficient roofing would be built globally. These efficient roofs could reduce carbon dioxide emissions by 800 megatons at a cost of $1.4 trillion, thirty-year savings of $988 billion, and lifetime savings of $3 trillion
A cool roof is a roofing system that is characterised by high solar reflectance and high infrared emittance and delivers cooling energy and financial savings, improved thermal comfort conditions, mitigates heat islands and reduces air pollution.
Α Cool Roof minimises solar heat gain keeping roof surfaces cooler under the sun. This is due to the materials used, which both reflect the solar radiation (solar reflectance) and release the absorbed heat (infrared emittance)
The EU itself is proposing action to implement an Action Plan to promote cool roofs technology in EU. The specific objectives are: to support policy development by transferring experience and improving understanding of the actual and potential contributions by cool roofs to heating and cooling consumption in the EU; to remove market barriers and simplify the procedures for cool roofs integration in construction and building’s stock; to change the behaviour of decision-makers and stakeholders so to improve acceptability of the cool roofs.
Results of an EU research project indicate a possible -40% in cooling effect and +10% heating impact -overall a 30% energy reduction. A further advantage is greater thermal comfort.
Cool Roofing products can be applied to all types of roofs including those of residential buildings,apartment blocks, industrial structures, commercial buildings, hospitals, and offices.
The “EU Cool Roofs Council” (EU CRC) has been established to promote cool roofs more widely.