Invest to reduce your bills (2ieme part)
Heat pumps: more and more attractive?
It is also possible to supply a central heating installation by floor or by radiators with a heat pump (PAC). These devices use the heat of the air or the ground (even low) to heat the water in the circuit. A heat pump uses electricity for its operation and is characterized by its coefficient of performance (COP), i.e. the ratio between the heating energy produced and the electrical energy consumed.
A COP of 3 means that 1 kWh of electricity provides 3 kWh of heating; in other words, that two thirds of your heating is free (excluding the initial investment). The most efficient heat pumps have a COP of around 4,6. For ground-water heat pumps, using heat from the ground by means of sensors buried at 1 or 1,50 m, “at least 1,50 m2 of land per m2 to be heated must be available, for example 180 m2 for sensors necessary for a house of 120 m2 ”, warns Gilles Walterspieler, of the company Viessmann, a manufacturer.
The initial investment represented by a heat pump is high: count, for a new house of 120 m2, around 18000 euros: at the heat pump (around 6 euros), you must add the heated floors (000 € / m65) and, for a ground-water model, the sensors (2 euros), plus their location in the field (3200 euros).
A tax credit of 50% on the CAP.
This bill is nonetheless reduced by a tax credit of 50% on the CAP (if its COP is at least 3), and 25% on sensors (from 2006), which puts the final score at Around 14200 euros (or 118 euros / m2). Long reserved for new constructions, the installation of a heat pump is now possible to replace an existing boiler, supplying heating by radiators (and not by heated floors). It is then necessary to invest in a “high temperature” pump (approximately 10000 euros, plus the sensors and earthworks).
These devices require advanced skills from the installer: "A Qualipac label should see the light of day in 2006, but in the meantime you must rely on word of mouth", notes Jean-Marie Carton.
Existing and new: play the solar card for hot water.
The boilers generally produce hot water instantaneously, which is more economical than a tank maintained at temperature (there is no heat loss) but less comfortable so two showers cannot be supplied simultaneously. It is then preferable to complete the boiler with a tank of reduced capacity, from 50 (wall-mounted boiler) to 100 liters (floor-mounted boiler), at an additional cost of 500 to 1000 euros, rather than ensuring the production of hot water by an independent electric balloon. Another choice, in the new as in the existing, the installation of a solar water heater, which can satisfy, according to the regions, from 50% to 70% of the needs in domestic hot water (DHW), in addition to your current installation.
For a family of four, it is necessary to provide 4 m2 5 m2 sensors and a ball of 300 liters, between 4500 euros and 5000 euros. In some cases, a subsidy from the Region or the Department will be deducted, and always a tax credit (50% from 2006). Depending on your region and the energy currently used to heat your water (electricity, oil or gas), the return time of this investment is from 10 to 15 years (7 to 10 years if energy prices increase further 50 %). Beware, solar water heaters arouse a strong craze, resulting in installation time that can be long, and installers tents to inflate prices.
The advantages of insulation from the outside.
With the choice of economical heating, the other way to reduce your energy bills is to insulate the building.
If you are building, opt for exterior insulation instead. walls, which protects the insulating material from bad weather (only the roof remaining insulated from the inside). "A polystyrene insulation can be covered with a simple coating, which is less expensive than a cladding", indicates Bruno Peuportier, researcher at the Ecole des mines de Paris. The cladding (steel, aluminum, wood, stone, etc.) remains necessary with an insulation such as glass wool. About twice as expensive as interior insulation, exterior insulation is more effective because it eliminates thermal bridges, which cause energy loss (for example, at the junction of floors and facades). Therefore, the exterior insulation will facilitate, in new construction, obtaining the level of performance required by RT 2005. It also avoids the presence of 15 to 20 cm of interior insulation, which can lose up to 4 or 5 m2 of living space, notes Marc Casamassima, from the Environment and Energy Management Agency (Ademe).
On the other hand, insulation from the outside. of an existing construction may come up against architectural and / or administrative constraints (it modifies the facade and it must therefore be the subject of a building permit) which could require you to insulate from the inside. As a priority, insulate the roof, or, in the event of lost attics, their floor: “We can use up to 30 cm of insulation in the attic. Beyond that, the gain is negligible ”, considers Alain Bornarel. Allow around 8 euros / m2, installation included, for 25 cm thick mineral wool.
Insulating the walls is more expensive - from 10 to 15 € / m2 for 10 cm of mineral wool, plus around 250 euros / m2 of finishes - and involves a significant building site. "This is why you can choose to only insulate poorly exposed walls, suggests Jean-Pierre Bosquet, president of Architectors, the heating savings to be expected from this work, and, consequently, their return time being difficult. to evaluate. »Prefer conventional insulation, glass wool and polystyrene, to more experimental materials such as hemp and linen, or thin insulation (10 mm), made up of an assembly of several layers of aluminum foil, these are more delicate to implement and are not subject to quality guarantees such as Acermi or DTU certification (unified technical documents) and technical advice from the Scientific and Technical Center for Building (CSTB).
Finally, only traditional insulators are entitled to the tax credit (40% from 2006), provided that the housing has been completed for more than 2 years.
Invest in quality double glazing.
Another source of heat loss is the windows. Instead of conventional double glazing (called 4-16-4, because it is made up of two clear panes of 4 mm spaced 16 mm apart), reinforced insulation glazing (VIR), also called "low emissivity". "With 0 ° C outside, it is 5 ° C next to a single-glazed window, from 11 to 12 ° C with classic double glazing, 16 ° C with a VIR, explains Martine Olivier, head of produced at Saint-Gobain Glass, and even around 17 ° C with an argon VIR. ”(Models where the space between panes is filled with argon, more insulating than air). For the price, a 100 x 135 cm double-leaf PVC window fitted with VIR plus argon double glazing costs 180 euros, compared to 140 euros for a classic model.
The additional cost is therefore minimal, whether in new construction or in existing ones (or a change of window costs 900 to 1000 euros per unit, additional work and labor included). In addition, in the existing, the price of VIR can be reduced by a tax credit (40% in 2006; homes over 2 years old). As with wall insulation, the size of the investment and the difficulty of estimating the resulting savings may lead to replacing only certain windows. Knowing that the most obvious gain is the comfort of the accommodation. In winter, the suppression of the feeling of cold felt near poorly insulated windows which often encourages the heating more than necessary. In summer, this reinforced insulation will prevent or limit the use of an air conditioner, which consumes electricity.