ENERGY EFFICIENCY AND RENEWABLE ENERGY

General considerations

Energy efficiency is a major concern and an essential component of green building. It has even become a major factor in its success. A green building must always be fitted with solutions that offer enhanced electrical energy management, reduce consumption and contribute to supplying quality energy. 

This efficiency can be materialised in a home through the use of occupancy detectors and full home automation systems. All these solutions help to manage and programme lighting, heating and other uses to optimise their use at a lower cost. In commercial buildings, solutions are multiplied to reduce energy use and contribute to reducing greenhouse gases, both in lighting management, office equipment management, security lighting, infrastructure measurement and surveillance. In such buildings, capacitor banks increase the efficiency of the installation and network analysers make it possible to measure the consumption and quality of the energy.

Renewable energy sources present the advantage of being available in unlimited quantities. Their use is a way of satisfying our energy needs while conserving the environment. The main forms of renewable energy are solar power, wind power, biomass power, geothermal power, hydraulic power, etc.

The energy produced by photovoltaic panels is an undeniable component of renewable energy production, which must satisfy the dual issue of integration into buildings and optimised production. Heavy investment in various clean energy technology projects around the world have been undertaken to improve the efficiency of renewable energies, to reinforce the economy, protect the environment and reduce our dependence on oil products.

Energy efficiency and green building

Waste

For the past 10 years, observers have complained about peaks of energy consumption due to air conditioning equipment. Among other factors, they point out unsuitable dimensions, non-existent or unsuitable cleaning and maintenance, the use of obsolete and energy-inefficient technologies. To stop energy waste, air conditioning systems are subject to regular inspections. In effect, a decree and law now require that owners have their units regularly inspected, every 5 years at least, by a certified technician. 

In France, this concerns decree 2010-349 of 31 March 2010 and the administrative order of 16 April 2010. These legal texts continue the enactment of the European Directive on Building Energy Performance in French law and the implementation of the Grenelle Environment round table recommendations. The aim is to end wasteful use of energy. Air-conditioning systems and reversible heat pumps with a rated cooling power above 12 kW are equipment for home comfort. Their energy use is not in proportion to actual needs, either because they are incorrectly dimensioned, or that they are not correctly maintained or managed. Cooling systems for computer rooms and industrial use are not concerned by these texts. Waste is not welcome in a green building.

Specific electricity

Specific electricity corresponds to that required for services that can only be provided through the use of electricity. Items that are not taken into account in specific electricity include hot water, heating and cooking, which can use other types of power. Specific electricity consumption has doubled over the past 20 years and this trend is likely to continue. Choosing energy-efficient appliances is therefore of great importance in a green building.

Efficient appliances will make significant savings on the specific electricity bill. For example, the savings generated by low energy lamps reduces costs by a factor of 4 compared to incandescent lamps. For cooling appliances, the difference in consumption between two different new machines can be anywhere from 1 to 3. Note also that a new appliance can consume up to six times less than an aged appliance.

Energy savings

By energy savings, we mean all economically interesting actions undertaken to reduce energy consumption, by for instance installing suitable equipment in electrical installations. The aim is also to consume energy in an optimal manner (e.g. recuperate heat lost in combustion gases or produce energy from waste). We should be aware that energy savings do not concern just electricity. Adopting some simple daily habits along with a judicious choice of equipment also enables us to control consumption of all other forms of energy (gas, heating fuel, etc.). In a green building, the main priority is to identify energy savings.

Some of the main measures that enable energy savings are:
•    Good thermal insulation of all exterior components (walls, windows, roof, etc.)
•    Eliminate thermal bridges and other energy leaks
•    Good airtight seal on the exterior building envelope
•    Reduction of thermal losses through ventilation
•    Efficiency of a reduced-inertia boiler
•    Optimised electricity management (reduction of installed power ratings, central management, use of lighting control equipment, etc.).

Renewable energy

Solar power systems

Solar energy is the source of the water cycle and of wind. The plant kingdom, on which the animal kingdom depends, also uses solar energy by transforming it into chemical energy through photosynthesis.
Apart from nuclear power, geothermal energy and tidal power, solar energy is the origin of all other energies on Earth. Solar energy is also inexhaustible on a human timescale and hugely abundant. It is estimated that the Earth receives from the sun about 10,000 times the total amount of energy consumed by all of humanity. Solar power capture technologies can be split into three categories: Solar photovoltaic, solar thermal and solar thermodynamic. The use of solar power is of tremendous importance in a green building.

Solar heating systems can be installed in all types of buildings. Using solar power to pre-heat outside air before it is allowed to enter a building can considerably reduce heating costs both in residential buildings and commercial constructions. Solar heating systems are especially efficient for large buildings such as hospitals, hangars, school and gyms, as well as multi-storey residential buildings. To make solar electricity available on a large scale, scientists and engineers around the world have been trying to develop a low-cost solar cell for many years. Such cells must be very efficient and easy to manufacture, with a high yield.

The vast majority of solar heating systems require the installation of solar walls. Such equipment can be installed on new or existing buildings. Solar walls require very little maintenance, feature no liquids or detachable parts other than the ventilators connected to the ventilation system. Moreover, solar walls can operate under cloudy conditions and at night time, even if their efficiency is much less. The ROI is two years due to the energy savings they produce.

Geothermal power

Geothermal energy is extracted from the ground for use in air conditioning, heating or transformation into electricity. Installing a geothermal heat pump system represents a major investment, but it enables users to make use of an inexhaustible source of energy that will provide 60 to 70% of the power required to heat a building. Geothermal systems can be installed on new houses or renovation projects. This technology can therefore considerably reduce the use of fossil fuels or electricity, which emit much more greenhouse gases and which are generally less financially interesting in the long term. Geothermal technologies are naturally included in green building parameters.

Geothermal systems present some major advantages. Effectively, underground heat is present everywhere on Earth. Geothermal energy comes from an almost continuous source that is not dependent on atmospheric conditions. The ease of extraction of this energy depends on the structure of the geological formations or the composition of the rock beds. This technology is split into two categories: Deep geothermal or near-surface geothermal energy.

Other energy sources

Alongside solar energy and geothermal energy, wind power is the third major source of green building energy. Today wind power is the least expensive clean energy to produce, which explains the strong enthusiasm for this technology. Current research could enable it to keep this comfortable head start for several years to come. Water or hydraulic power is mainly produced by the displacement or accumulation of fresh water or sea water. As it is everywhere, water plays an extremely important role in transporting the Earth’s energy.  

Biomass is generated by photosynthesis, where solar energy is stored by plants in the form of carbohydrates, as they use the carbon dioxide in the atmosphere. In a wide sense, the expression “biomass” refers to all living matter (the total mass of living matter). In terms of energy, biomass refers to all organic material that can become a source of energy in the form of biogas, biofuel or directly by combustion: Wood or organic agricultural or urban waste, etc. Biomass energy is used by the biogas, biofuel and wood industries.

The radiant system is a comfortable heating system. Radiant heating transfers heat directly from the floor to your body as well as heating the ambient air. Radiant heating systems produce uniform temperatures in all rooms or heated floor areas, in all seasons. Radiant heating is also a technique to prevent the transmission of dust and pollen, which are prevalent in warm air heating systems.

SUSTAINABLE MANAGEMENT

Sustainable water management

Water savings in a green building

The availability of fresh water has become a matter of increasing concern in a context where developed and developing countries are engaged in a race to obtain resources that are inexorably becoming scarcer. A green building must therefore be designed to use water efficiently. Managing waste water, irrigation water and rain water are also essential for a sustainable approach.

The use of mixer taps reduces water consumption as it is easier to control the temperature. Aerator tap fittings reduce the amount of water used without it being noticed during use. Waste through negligence is to be avoided. Even if repairing a leaking tap can be a chore, tens of millions of cubic metres of water are lost every year, just in France, because of inadequate seals on taps.

Thermostatic mixer taps can also generate savings. As water runs at a predetermined temperature, the water that is usually lost when adjusting a shower temperature is saved. An efficient and sustainable water-saving approach also depends on existing knowledge or projections of water use, tracing and preventing leaks. Replacing unsuitable equipment and using water-efficient devices, communicating and raising user awareness are also potential sources for water savings.

Recuperation and use of rain water

Rain water is an inexhaustible natural resource which has its place in the green building. Rain water is collected as it runs off a roof and is stored in a tank. Whether polluted or not, rain water is naturally slightly acidic (pH from 5 to 6), due to its carbon dioxide content, present in the atmosphere. This acidity means it should not be stored in plastic or metal containers. For domestic use, the ideal solution is a concrete or limestone tank that neutralises the natural acidity of rain water.

Rain water is only rarely recuperated and often only used for watering gardens. Its use should nonetheless be systematic both to unblock waste networks and to save on a resource that is becoming scarcer and is weighing on household budgets. A farmer’s common sense has always encouraged them to put a container under the gutter pipe to recuperate rain water. If optimised, rain water collection can enable homes to be autonomous in water use, without it being visible or visually un-aesthetic. 

In certain buildings, rain water is recuperated, treated and reused in applications that do not require potable water. This kind of solution helps reduce fresh water needs in the public network, while avoiding the propagation of pollutants by run-off. Other solutions are available, such as green roofs, which not only store rain water, but also provide a green oasis in an urban environment along with many other benefits.

Reduction of waste and toxic substances

A good green building design helps the occupants to reduce the quantity of waste generated. It also offers solutions such as composting bins, to reduce the volume of matter going to landfills. The green architect also aims to reduce waste in terms of energy, water and materials used for the construction. This considerable reduces the volume of waste sent for disposal during the construction phase. Green building avoids the systematic burial of materials retrieved from buildings at the end of their life by recycling and recuperating them. The extension of the useful lifetime of a structure also enables waste reduction.

The quality of interior air is an important factor in a green building. To do this, it must also seek to reduce volatile organic compounds (VOC) and other air impurities such as microbial contaminants. The ventilation systems must be well-designed to ensure suitable ventilation and air filtration, as well as to isolate certain activities (kitchens, dry-cleaning, etc.) from other applications. 

During design and construction, the choice of construction materials and interior finishing products is made to reduce the amount of toxic substances in the building. In effect, many construction materials and cleaning products emit toxic gases such as VOC and formaldehyde. These gases can have a negative impact on occupant health. By avoiding these products, we can increase the quality of the interior environment in a building.

CONSTRUCTION MATERIALS USED ON A GREEN BUILDING

Wooden structure

Wood occupies a primordial place in the green building approach. There are many different possibilities in terms of wooden structure. We can opt for walls with solid wood beams, wall with glued and laminated timber, and the wooden frame structure, which are suitable for an urban environment as from the outside they look identical to a conventional construction. The foundations of these constructions are made of concrete.

The benefits reside in the fact that wood is a clean material that generates neither radon nor static electricity. Wood protects itself naturally as it contains polyphenols of vegetal origin, which have a disinfectant effect. It is also an excellent thermal and hygrometric regulator, regulating ambient humidity like other green building construction materials.

One of its many benefits is its lightness. Wood also resists well to traction and compression along the axis of the tree from which it came. It offers high insulation properties, which enables the construction of thinner bearing walls. Wood offers good insulation both in winter and summer by naturally contributing to the thermal inertia necessary to keep warmth inside during the winter and maintain coolness in summer. It can significantly reduce heating consumption in winter.

The insulating load-bearing clay brick

Bricks are becoming more important in the green building approach. The insulating load-bearing clay brick (“monomur” brick) does not need insulating cladding on either the inside or the outside. It is a self-insulating material. The thermal insulation produced is in fact a combination of insulation and thermal inertia achieved by multiple air holes and extending the thermal path crossing the wall. As a resistant and durable heat regulation system and humidity barrier, the insulating clay brick displays admirable performance. Its efficiency is clearly demonstrated today through many tests and studies.

In addition to all these benefits, the insulating clay brick also offers a technology that simplifies its deployment, respects all construction regulations and makes this material a future concept that is increasingly appreciated by builders. It presents a highly reassuring safety rating. In the event of flooding, the characteristics of the insulating clay brick remain intact after drying out, which is not the case with interior insulation. Without additional insulation, the insulating clay brick is totally non-combustible. It emits no toxic gases in the event of fire. Insulating clay brick elements can easily be used to build buildings that must comply with seismic protection regulations.

The clay brick is a natural temperature controller that retains its properties throughout its lifetime. In winter, the brick absorbs heat from the heating system and redistributes it gradually by radiation, reducing energy consumption by about 10% whatever the source. In summer, it naturally regulates the temperature and retains the coolness offered by nocturnal ventilation all day long, due to its excellent thermal inertia, but on condition that heat is not permitted to enter during the daytime by opening the windows.

Cellular concrete

Cellular concrete, sometimes referred to as aerated concrete, is a lightweight concrete that is very interesting for green building. It is a combination of water, siliceous sand, cement, lime and air. The lime reacts in contact with the aluminium powder present to 0.05%, emitting hydrogen gas to create the air bubbles. After hardening, the material is fairly light with a density of 400 Kg/m3 as it contains thousands of trapped air bubbles (up to 80% of its volume), and offers excellent thermal characteristics. Also, the expansion agent produced by recycling after chemical bonding with the lime, forms non-toxic calcium aluminates. 

The materials used in its manufacture make it an eco-material as it respects the environment. It is 100% recyclable and can be used to cover rubble without risk of polluting soils.  Cellular concrete offers a high thermal inertia and enables efficient correction of thermal bridges. It also offers exceptional resistance to fire, in excess of 6 hours. Soundproofing taken into account in the HEQ approach is 49 dB.

The sound-damping performance of these blocks satisfies the most stringent requirements of acoustic regulations in effect for exterior walls. Cellular concrete is a natural mineral, non-combustible material. It offers remarkable protection against fire and its frequent use in industry and buildings requiring such protection is highly appreciated. A wall built of cellular concrete is water tight and can breathe. It is a real humidity regulator: It softens dry air by releasing gas and absorbs excessive humidity in a damp atmosphere. It therefore creates a healthy, pleasant atmosphere throughout the home. 

A major benefit of cellular concrete and what sets it apart from other materials is how it controls interior temperatures through thermal inertia. The thermal inertia of this material guarantees high attenuation of external temperature variations. It has an excellent capacity to accumulate heat and return it. This can help reduce the amount of time heating is used in half-season and can even offer natural temperature control in summer.

The Euromac2 structure

This construction system comprises two insulating cladding walls made of high density expanded polystyrene, joined by two metal spacers that are reinforced in their lateral parts by flat metal bands. Then concrete is poured inside the cladding up to a height of 3.6 metres in one go. This wall system is totally seismic-protected and has a variable width of 0.25 m to 0.45 m, with excellent acoustic and thermal insulation properties. 

Aside its exceptional thermal insulation properties, it offers excellent acoustic insulation and a fire-retardant effect from 90 to 120 minutes, depending on the thickness of the wall. It naturally insulates the outside from the inside, eliminating all thermal bridges and offering full protection to the construction. This type of construction method can be used for high buildings (up to 10 storeys) and underground basements.

With its reinforced insulation concept for all exterior walls and the slow inertia of its walls, Euromac2 (walls, floors, roofs) is particularly effective for BBC (low energy) buildings (Effinergie, Minergie and passive house certificates) and suitable for green building projects.

GREEN BUILDING – Ecological construction
GREEN BUILDING – Components
GREEN BUILDING – Environment and climate
GREEN BUILDING – Certifications
SUSTAINABLE DEVELOPMENT AND THE ENVIRONMENTAL FOOTPRINT
GREEN BUILDING – Green installations
GREEN BUILDING – Eco-technologies and practices
GREEN BUILDING – Zero energy home and economic aspects