“Green building” to save energy

Green building consists in designing energy-efficient and environment-friendly buildings, thus combining energy intelligence with sustainable construction. Here is an overview of various design processes involved in green building.

Energy-efficient building

According to figures published by the French Ministry of Ecology, Energy and Sustainable Development on February 21st, 2013, the residential and tertiary sector accounts for 44% of final energy consumption, making it the largest potential source of directly achievable energy savings. To that end, two options are available: on the one hand, renovating existing buildings with a view to optimizing their energy efficiency, as provided for by the “Grenelle I” bill from August 3rd, 2009; on the other hand, building brand new sustainable infrastructure.

The US Environmental Protection Agency (EPA) defines green building, also known as green construction or sustainable building, as “the practice of creating structures and using processes that are environmentally responsible and resource-efficient throughout a building’s life-cycle” from construction to operation, maintenance and deconstruction.

The main goal of green construction is to ensure building energy efficiency through specific construction processes aimed at reducing a building’s energy consumption and improving its capacity to capture or even generate energy.

Reducing energy use through thermal efficiency

Heating is the largest source of energy consumption in buildings: it represents 66% of energy needs in the residential and tertiary sector, according to figures published by the French Ministry of Ecology in 2007. By way of comparison, hot water and cooking only account for 14% while specific electricity consumption (lighting, air-conditioning…) make up 20%. Good thermal insulation prevents heat loss and is therefore a simple and inexpensive way of cutting energy use. Thermal inertia can be achieved by using false ceiling panels, mineral wool or hemp insulation as well as double-glazing windows, thus mitigating the impact of outside temperature variations. Thermal bridges, also called cold bridges, i.e. leaks in the insulation layer, can be mitigated by external insulation, for instance an “insulating mantle” made out of bricks and polystyrene. Additionally, a ground heat exchanger can be used to heat or cool down the ventilated air by using the earth’s thermal inertia.

However, insulation is not the only energy-efficient solution. Taking advantage of sunlight is another way of reducing energy use related to heating and lighting. It can be achieved by designing buildings in ways that make them capture the most sunlight, which in turn can be used as heat. This passive solar energy can be captured mainly by thermally efficient windows facing the sun as well as heat-absorbing materials. Such solutions aiming at reducing heating-related energy use are part of so-called passive-energy housing, i.e. houses using less than 15kWh of primary energy per m² per annum for heating and less than 120 kWh per m² per annum for overall energy use.

Housing; Energy Efficiency; Energy Savings; Electricity Consumption; Photovoltaic

Energy-sufficient buildings

On top of passive solutions, green construction includes active ways of designing thermally efficient buildings; the goal is to enable buildings to generate their own energy.

Energy-sufficient buildings take advantage of their environment by using renewable energy sources. They can generate electricity and heat thanks to active solar energy, respectively using photovoltaic and thermal panels attached on the roof. Heat pumps are another means of generating heat, while wind turbines provide an extra-power input. Sigma Home, an advanced kind of energy-sufficient house equipped by Rexel, is a telling example of how a building can rely on various renewable energy sources. The Vauban and Rieselfeld neighbourhoods in Freiburg im Breisgau, Germany, feature sustainable housing at the scale of a city.

The long-term goal of green construction is to create positive-energy buildings (in French BEPOS for “bâtiment à énergie positive”) capable of generating more energy than they use. Anticipating future energy transition regulation, the NGO Effinergie developed in February 2013 the BEPOS standard for buildings whose use of non-renewable primary energy is inferior to the amount of renewable energy they produce.

For more information:

Bookmark and Share

About admin