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Green building – Zero energy home and economic aspects

Zero energy home



Buildings have a relatively long lifetime compared to consumer goods. The selection of green construction methods and materials therefore has an impact over a very long period of time. The choice of construction materials is important insofar that materials with very high thermal inertia must be selected, as they insulate efficiently against the cold in winter an heat in summer. Their environmental performance is also a determinant factor.

An environmental approach to construction always results in savings in terms of maintenance and operating costs. This approach does not forcibly entail additional initial investment. One of the following structural materials must be used to build a green building:

•    Cellular concrete: Load-bearing material offering thermal insulation, of mineral origin. It is durable, recyclable and produces no toxic discharges.
•    Clay bricks (honeycomb brick): Load-bearing clay material offering thermal insulation. Offers high acoustic performance and highly durable. Incurs overconsumption of grey energy in the manufacturing process.
•    Wooden frame: Load-bearing material (requires systematic addition of an insulating material) and CO2 absorbent. A renewable source available in large quantities.

Choice of energy

Here it is not a question of total energy independence from the electricity supplier but to produce as much energy as the building consumes on average over a given period of time.  The green building that produces as much energy as it consumes on an annual basis is equipped with passive solar power features such as south-facing windows.  Combined with solar panels, these systems concentrate the sun’s energy to produce electricity, heating or air conditioning.

In certain countries, solar rays captured by an average house, over a year, are sufficient to satisfy its energy needs and more. It is now possible to reduce the average energy consumption of a green building to zero by using solar power. In a green building, reduced energy consumption must be accompanied by the use of all energy efficiency measures possible.


For heating purposes, it is important to prioritise renewable energies, especially in new construction projects. In this respect, solar power, wood-energy and geothermal sources seem to be the most suitable. With plenty of solar power in a green building, we can propose hot water and a direct heated floor for heating.

Panneau solaire

These days solar water heating systems are extremely efficient, even if we can regret that the maximum yield is in summer when we need it least. This solar energy is free, clean and inexhaustible. It can cover a part of a green building’s heating needs. In this context we refer to combined solar systems. They can cover from 25% to 60% of annual needs in terms of heating.

The combined solar system is more complex to set up insofar that we need hot water all year round but heating is only needed for several months. Similarly, the temperature of water in the heating circuit is rather low (between 30°C and 50°C) while for hot water it is much hotter (between 45°C and 60°C). To remedy these difficulties, hydro-accumulation systems have been created. This system consists in stocking the heat produced by sensors in a buffer water tank, which we can tap into in the event of necessity. The energy required for heating is distributed around the building either by low temperature radiators or via direct-heated floors.

Paysage montagne arbre

Wood energy is a renewable energy that contributes to reducing the greenhouse effect and climate change. It recycles the carbon dioxide in the atmosphere which is then absorbed by forests. What is more, its constitutes and excellent method of valorising by-products and waste from the wood industry and participates in rational forest management, therefore to maintaining hydrological and climatic balances.

Geothermal power is also a renewable energy, environmentally-friendly and available on demand. Geothermal heating collects heat from the earth or water, in the case of a geothermal system on a water table, to transform it into useable heat in the green building, via a generator that supplies the heating system. Geothermal heating offers solutions that are suitable to most constructions.

The economic aspects of a green building

Cost of a green building

Usually, the ecological properties of a building are considered as an additional cost. In this vision of things, the construction of a green building is inevitably more expensive that a less eco-efficient solution, as it implies the use of high quality materials, high efficiency materials and a more complex work flow. The approach that consists in considering that the payment of a supplement is inevitable to make a project eco-sound is now fading away to allow more holistic designs and a global vision of project costs and benefits.

Today, research scientists, architects and owners observe that a program that is oriented to sustainable development from the outset may enable us to discover techniques that will bring environmental and social benefits without additional costs. For example, by simply orienting a building to exploit its windows and capture passive solar heat as much as possible, promoters and architects can create their designs with a mind to consume less energy, increase the sustainable development aspects and improve daylight penetration, which can increase employee productivity without incurring additional construction costs.

A green building can even help the owner eliminate expenditure from the outset. The choice of cooling equipment is a good example. In this way, if heat losses on an eco-construction project are reduced to a minimum through efficient lighting and the building envelope is eco-efficient, the building will need a much smaller cooling capacity. This can therefore avoid having to install an additional cooling system and can even reduce the project budget significantly.

The benefits of a green building


The construction of a green building may generate only few additional costs, even none, but that is not due to spontaneous generation. The required evolution in processes to design and construct a building with an integrated approach requires a great deal of effort and must be perceived as having sufficient added value to be adopted by the industry. Rightfully so, owners and promoters wish not only to be assured that a green building will not cost them much more, but they also wish to be sure that it will produce substantial benefits that will justify their efforts.

Of course, one of the benefits of a green building is to be able to use it as a showcase for public relations. People interacting with companies and organisations now expect to see a certain degree of environmental action. A green building conveys a physical and permanent message on a company’s commitment in terms of stewardship and environmental responsibility.

Concerns due to climate change encourage governments to enact laws that impose measures to reduce carbon emissions. Similarly, shareholders are increasingly demanding that businesses manage their environmental and carbon footprints responsibly, as well as anticipating the risks of climate change to which they are exposed. The construction of a green building can help owners to comply with these requirements.

These advantages help demonstrate the value of a building, but do not always suffice to motivate an owner to adopt an eco-construction approach. As with any financial decision, the return on investment is crucial. However, in many cases, eco-construction is a byword for energy savings and potentially significant savings can help the owner to cross the eco-construction line.

When a green building is designed to optimise efficiency and reduce the use of resources to a minimum, it must produce a lower energy bill. It is commonplace that the energy bill be half as much as that for a building built according to minimum standards. This bill will drop even further when on-site generation of renewable energies is included in the project.

Nonetheless, these energy savings generally benefit the building occupants and not the architect or the entrepreneur. To alter this erroneous perception of the cost/benefit ratio, recent studies have attempted to quantify the value (for the owner) of a green building, using measurements done by the whole property sector. Below are some of the conclusions drawn by this study:

•    Ecological buildings sell at a higher price. McGraw Hill measured the price premium on the sale of Energy Star buildings and obtained a result of 12%. Another study estimated the price premium on LEED-certified buildings at 31%.
•    Rents on ecological buildings are higher. By comparing lease contracts on Energy Star buildings with those on non-Energy Star buildings, researchers at Maastricht University observed that rents on eco-efficient buildings were 3.5% higher than others.
•    Ecological buildings are more attractive for occupants. The same study revealed an occupancy rate 6% higher for Energy Star-certified buildings.

Given that available data is increasing and that building owners are succeeding in assessing the benefits of a green building more effectively, an increasing number of projects will follow this path. As part of a new integrated design approach, it is possible to reduce the additional cost of ecological buildings to a negligible level. What is more, the benefits are increasingly visible and tangible. The two variables of this equation are progressively but inevitably leading us towards an era of construction of sustainable buildings. Real estate professionals have realised this and the increase in eco-buildings will results in more sustainable urban habitats all over the world.

By ensuring the continued improvement of the methods of selecting construction locations, design processes, construction methods, operating methods and modernisation techniques, political leaders should support the green building approach. The application of leading edge eco-efficient techniques may generate enormous reductions in the demand for fossil fuels and in greenhouse gas emissions. Design and construction best practices can also assist in resolving environmental problems related to the exhaustion of natural resources, the elimination of waste and the pollution of the air, water and soils. The growing “ecologisation” of the building industry may help to improve human health and prosperity.

In March 2011, the Fukushima accident in Japan was a stark reminder to us all that electricity production involves risks. In light of the environmental limitations and the increasing scarcity of non-renewable resources, the green building approach must pursue its development. This type of eco-construction is not an alternative, but rather the only way of meeting the environmental challenges that we face.
Fortunately, to do this, we can count on the environmental commitment and the continued development of solutions offering maximum energy efficiency, from such organisations as the Legrand group.

Copyright protected by articles L.111-1 and L. 123-1 of the French Intellectual Property Code.

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