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 and how they manage their consumption. Passive measures take time, require a holistic approach and can be very expensive. Active measures are less costly (or, indeed, cost-free), and deliver immediate gains.
Active Methods: Focus on the User
The originality of active measures is that the building's occupant is directly involved.1 This crucial role depends on three core elements:
- Measuring Consumption. The "smart" electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor... and gas meters being phased in in many countries can accurately identify different sources of consumption such as heating, hot water, air conditioning, lighting, and other household appliances. They enable electricity companies to fine-tune their plans and will make it easier to manage new usages, such as the integration of locally generated solar powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output..., and electric car charging. In France, eight million Linky electricity meters are to be fitted by the end of 2017. Rollout has also begun for the Gazpar gas meter, to be fitted at a rate of two million units per year, replacing the eleven million existing meters by 2023.
- 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. A European study found that energy consumption by refrigerators dropped by 25% between 2005 and 2015 and that heat pump driers account for 42% of tumble drier sales in Europe (but only 13% in France)2. 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 construction and upgrading heating systems in existing buildings3. In France, such rules are set out in the "RT" thermal regulations, which have been periodically updated since 1974. RT 20124 is currently applicable, pending publication of RT 2020.
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 RT 2012 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 system5. The French RT 2012 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., a 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.
Under RT 2020, new buildings will have to be energy-positive, meaning that they must produce more energy than they consume. The energy may be generated by solar panels, heat pumps, wood-burning stoves, thermodynamic water heaters, etc6.
(2) TopTen study (in French only)
(4) “Comprendre la RT 2012” (Understanding RT 2012) (in French only)
(6) Article by energy saving advice website “L’énergie tout compris” (in French only)