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Mobile solar shading in building construction

November 1st, 2011 / By: / Awnings & Shades, Sustainability

The European Solar-Shading Organization is working to gain recognition for the merits of mobile solar shading in building construction.

A couple of months ago, the fuel bill at my nearby Shell filling station here in Brussels hit the 100 (euro) mark for the first time. In dollars, that’s around $140. And, yes, that was for one car only, a relatively modest 2-liter Audi. With regular gasoline at 1.55 euro per liter, this translates into about 8 dollars per gallon. This crossed my mind when I read the editor’s ‘Forethought’ column in the August issue, touching on the subject of lower air conditioning costs by using awnings, and suggesting that Europe is, or has been, more energy-conscious than the United States. Judging by the costs of gasoline, that’s not surprising.

The U.S. encourages but does not, in many cases, require energy efficiency, the editor noted when she invited me to submit an article. Well, here’s that first difference: Europe does require it, at least in some areas. The 27-member European Union is managed on a daily basis by the European Commission and controlled by the European Parliament, with the European Council (basically the heads of states and their Ministers) as the third—and most powerful—body. Aware that for too long we have been careless with our scarce energy sources, the European Commission launched its Climate and Energy Package in 2007, agreeing on the “20-20-20” targets for the year 2020: 20 percent reduction in greenhouse gas emissions, 20 percent share of renewable energy, and 20 percent less energy use. This cannot be done without improving energy efficiency, and as the largest energy user and the most potent carbon emitter, the built environment takes center stage. Just like in the U.S., it burns away more than 40 percent of all primary energy. Europe’s 200 million+ buildings occupy billions of square meters of floor surface and have an enormous effect on the environment, given their very long life cycle. Their potential for saving energy is colossal—and mobile shade systems are part of that solution.

Recasting energy performance

In 2002, the European Commission issued the Energy Performance of Buildings Directive (EPBD). A directive is a legislative act which member states then implement, taking into account national circumstances; when finished, it has legal force. Member states normally have three years to accomplish the directive. Among the original EPBD’s objectives were (1) the requirement to develop a method to calculate the integrated energy performance of buildings, (2) minimum efficiency requirements for new construction and major renovations over 1000 sq.m., and (3) energy certification of buildings. Due in 2006, the implementation has, to say the least, been hesitant. Some member states have dragged their feet, while the construction sector itself is “critically fragmented with significant inertia to change,” as an Intelligent Energy Europe publication cautiously states.

A revision of the EPBD was published last June, maintaining the original principles, clarifying and streamlining a number of provisions, extending their scope and strengthening certain requirements. Renewed emphasis was placed on the exemplary role of the public sector in promoting energy efficiency.

The “recast EPBD” will apply to all buildings and renovations, irrespective of size. The most surprising new requirement is this: by the end of 2020, every new construction must be “nearly zero energy,” while for the public sector this is compulsory even by the end of 2018. Moreover, for all existing buildings that undergo renovation, minimum energy performance requirements must be set at building, system and component level—which mainly applies to the building envelope. The minimum energy performance levels required for new buildings (until 2020) and for refurbishment must be benchmarked to achieve “cost-optimal levels.” Packages of measures will be considered cost-optimal when they lead to the lowest cost during the full life cycle of the building, including not just the initial investment cost, but also maintenance, operating and disposal costs.

The role of solar shading

A European directive will not promote specific technologies. But in the recast EPBD, solar shading is mentioned several times. Recital 9 deals with the characteristics that “play an increasingly important role“ in energy performance, such as “heating and air-conditioning installations, renewable sources, passive heating and cooling elements, shading, indoor air quality, adequate natural light and design of the building.” Recital 25 states that “recent years have seen a rise in the number of air-conditioning systems in European countries. This creates considerable problems at peak load times … Priority should be given to strategies which enhance the thermal performance of buildings during the summer period. To that end, there should be focus on measures which avoid overheating, such as shading and sufficient thermal capacity in the building construction.”

At the European Solar-Shading Organization (ES-SO), we have been working hard to gain recognition for the merits of mobile solar shading in the energy efficiency debate—not only by repeating the no-brainer that reducing the heat load on a building cuts the need for artificial cooling, but also by demonstrating that an automated mobile system can bring in welcome heat in the winter and contribute to our quest for renewable energy. Better use of free, natural daylight and avoidance of glare are additional benefits of properly designed and automated solar shading.

To harvest all these gains, both external and internal solar shading (roller blinds, shades, roller shutters, retractable awnings, etc.) should be considered. Retractable awnings in particular have gained a lot of extra attention as more and more European countries have adopted a “no smoking” policy for restaurants, cafés and bars. There is a growing market for outside terraces, covered by awnings and equipped with patio heaters (and ashtrays). “Al fresco dining” has been the new buzzword on restaurant menus, and the industry has responded with exciting new products and concepts.

There is a wide choice of fabrics available, and manufacturers have understood that it is not just the color and the weaving pattern that count, but also its technical capabilities, expressed in the g-value (or the shading coefficient) and the values of transmittance and reflectance, indicating how well the fabric performs in its role to limit solar heat gain. Building simulation computer programs such as Energy+ by Berkeley Lab, WIS (Window Information System) and TRNSYS or Parasol (Lund University) can help put a number on the amount of energy saved, even if that’s a bit more difficult for a retractable awning than for example, a roller blind which covers the whole surface of the window. It’s essential that these solar shading products are no longer just considered as accessories to the home or the office building, but as a part of a package of robust energy-efficiency measures.

Roadmap for renovation

As recently as September 20, the European Commission adopted its “Roadmap to a Resource Efficient Europe.” Among other subjects, it focuses on the existing building stock and raises the target for refurbishment to 2 percent per year, from a current estimate of 1 percent. Even at that higher rate, it will take 50 years to finish the job! Most of our time is spent living and working in buildings, and we expect them to be comfortable, practical, safe, healthy, energy-efficient, beautiful and sustainable—all at the same time. For existing buildings, this is a tall order, but the potential is huge. Existing houses and commercial buildings often show an annual energy use of 250 kWh/m2, and sometimes a lot more. Today’s readily available construction techniques allow for numbers well below 100 kWh/m2, with recent or soon-to-come regulations in France, Germany and Switzerland (to name only a few) requiring numbers at 50 or below for new buildings. The 2020 horizon for “nearly zero-energy building” is just around the corner.

That’s an opportunity that the awnings and shading industry may not miss. The recast EPBD will offer a sizeable market potential, provided we can see the writing on the wall. Simulation programs are available to help forecast the energy-saving effect of shading solutions. Several scientific case studies about on-site measurements and real energy consumption figures are on record or being assembled, proving the academic world’s interest in the effects of solar shading. It would be highly surprising if the U.S. were spared the energy scarcity situation and the tough choices on power generation that Europe is now facing. The industry must prepare to make a positive contribution to this societal problem, and join in its own growth as it happens.

Dick P. Dolmans is secretary general of ES-SO, and worked for many years for Hunter Douglas and in the building materials industry. He holds a degree in nuclear chemical engineering and a Master of Arts in economics, and has published many articles on the subject of solar shading and European building legislation.

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