Improving a building's energy efficiency can be achieved both through passive methods that enhance its intrinsic features, particularly at the time of design and construction, and active methods that depend on the user. These methods aim to manage equipment and electricity and heat flows more efficiently.
Passive methods take time, require a holistic approach and can be very expensive. Active methods are less costly, or indeed cost-free, and deliver immediate gains.
Active Methods: Focus on the User
The originality of active methods is that the building's occupant is directly involved.1 This crucial role depends on three core elements:
- Measuring Consumption. While traditionally, households had a central meter that gave them an overall reading of electrical consumption, the trend now is to break down a home's energy consumption into heating, domestic hot water, air conditioning, lighting, equipment, etc. In France, start-ups have been able to leverage the Linky meter to provide analytical systems and sub-metering of home energy costs. These tools ultimately enable users to identify possible savings.
- Regulating and Programing. Regulating heating serves to maintain room temperature at a desired level while taking into account changes in the outside temperature and free heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter... gains from the sun, electrical equipment, lighting, etc. Programing complements regulation by enabling the heating in each part of the house (bedrooms, living room, bathrooms) to be managed according to activities and hours of use. Programing also applies to lighting and to electronic equipment in standby mode.
- Changing User Behavior. Accepting to live with a degree less of indoor heat in the winter and a degree more in summer reduces consumption by 5% to 10% according to the French Environment and Energy Management Agency (ADEME). The choice of equipment also has a big impact. The 2013 generation of household appliances consumes 40% less on average than the 2000 generation. The energy consumption of refrigerators and freezers has actually been reduced by two-thirds over the same period, although the savings achieved have been offset by these appliances’ greater sophistication and more widespread use. Energy-saving light bulbs have cut consumption by 50% compared to incandescent bulbs, and LEDs will reduce consumption by 75% (see Close-up: In Our Daily Lives).
Accepting to live with a degree less of heat indoors in winter can result in energy savings of5% to 10%
Passive Methods: Renovation and Construction Standards
Improving the intrinsic features of the housing stock involves drafting stricter regulations for new construction2 and upgrading heating systems in existing buildings.3
Key paths being pursued today include:
- Situating buildings properly in relation to the sun, with a minimum amount of window area and careful management of sunlight. In addition to shade screens adaptable to building facades, manufacturers are working on electrochromic glazing that adjusts its tint to the amount of sunshine and the outside temperature.
- Managing the crucial combination of aeration and ventilation. For the first time in France, the RT2012 regulations impose an airtightness test to limit leakage as well as seepage. At the same time, the regulations stress the importance of efficient ventilation in order to avoid excess humidity and protect health. This means a double-flow controlled mechanical ventilation system that recovers the heat of the stale air extracted from the house and uses it to heat the incoming air from outside.
Ventilating a house is essential for reducing its heating needs.
- Ensuring effective thermal insulation, the essential first step before choosing a more efficient heating system.4 The French RT2012 regulations provide for the treatment of thermal bridges, or the continuity of insulation at the wall-floor junction in the case of interior insulation. Exterior thermal insulation, i.e., an insulating coat of polystyrenePolystyrene is a plastic with a wide range of uses, the most common being expanded polystyrene... covering critical areas like a second skin, is very energy efficient. The insulation is based on the design of more efficient materials with very small pore sizes, which prevent the movement of molecules. Phase-changing materials are also capable of storing the day's heat, by changing from solid to liquid, then releasing the heat in the evening by becoming solid again.