- A more insulating, inert and waterproof structure
- Positive points for concrete
- Ever larger joineries
- More efficient glazings
- An empty yet expensive
- Domestic hot water (DHW): recovering calories
- More tracks to follow
- Heating and ventilation: a winning duo
With the evolution of techniques and insulation materials, will we soon be able to do without heating? Not so sure... but solutions exist and reflection is progressing.
Due to the ever stricter requirements of thermal regulations (RT), the performance of homes has increased considerably in the new. Can we hope to do without heating?
For Jean-Louis Rasmus, product director at De Dietrich, the notion of heating is not about to disappear: "with the RT 2028 should emerge the NZEB *".
A more insulating, inert and waterproof structure
"These buildings, says Jean-Louis Rasmus, do not consume more energy (all uses combined) than they produce and constitute an intermediate stage between the passive houses and the BEPOS * which, they, produce more energy than they consume. But even they do not work without energy. So that their balance sheet is constantly positive, they must therefore consume very little ".
"In ten years the performance of insulators will have greatly improved again", says Alain Charpentier, market director of Recticel Insulation. "Which will therefore, equivalent heat resistance *, significantly reduce their thickness."
"Already today, he continues, polyurethane panels offer thermal performance up to twice as high at the same thickness ".
Tomorrow, products based on silica aerogels, also called Nanogels, may be five to eight times more efficient than traditional insulators... There remains the question of cost. It does not arise for vacuum insulation panels (PIV), but they have serious implementation constraints.
Positive points for concrete
In addition to the insulation of the envelope, many see the thermal inertia of materials as the key to multiple energy gains. Evidence for Michel Kratz, President of Euromac 2: "with all the devices in a house, plus passive solar gain - 30 m2 glazing in the South of the Loire equivalent to 10 kW of heating - the calories are already there. But not necessarily when we need it. Then there is the question of storage, which responds very well to the inertia of concrete ".
And David Poulain, director of marketing and communication for Rector Lesage, adds: "everyone knows the reversible floors: a principle that we can now combine, in the form of a predalle, to that of the radiant ceiling. use concrete for its inertia and enrich its use by integrating the circulation of fluids or energy in the form of technical sleeves freestanding, ready to assemble ".
A design that is no longer reserved for panels of wood frame constructions, even if it is limited for the moment to collective housing.
- These HD expanded polystyrene boulder blocks feature built-in reinforcement. They are implemented quickly but must be properly supported.
- Very good performance in 45 cm thick.
Ever larger joineries
With the RT 2012 appeared the consideration of solar contributions. And so, the need to increase daylight and enlarge glass surfaces. However, manufacturers have not waited for this text to work on this point: hidden openings have been around for quite some time. As for the profiles, they continue to thin and gain rigidity. "This is the case of PVC, some sliding bays now allow lengths up to 6.50 m" says Fabienne Riéra, marketing director of Veka.
- A double-opening carpentry offers excellent thermoacoustic performance. The interval separating the inner and outer openings can also easily incorporate a concealment device promoting the control of solar gain.
More efficient glazings
The limits seem however reached here also in terms of thickness. That's why this manufacturer is thinking about a system with two opening 70 mm superimposed on a single frame of 170 mm. The double window dates back to the 1930s but with today's products, we obtain a thermal transmittance Uw * of 0.52 W / m2.K. This gain is considerable compared to 0.76 W / m2.K a very good carpentry triple glazing today. The glass continues to evolve thanks to the applied treatments.
" After ensuring winter thermal comfort, then acoustic efficiency or burglary resistance and solar control, explains Valérie Vandermeulen from AGC, we can really talk now of multifunctional product ".
An empty yet expensive
Better still, the glass can be heated: Saint-Gobain Glass is in its second generation of radiant glazing. One of its faces is covered with an invisible and conductive metallic layer. It can therefore be traversed by an electric current (now supplied directly by the sector and no longer via a transformer), thus causing the glass to emit infrared rays, like any radiant panel.
Will all double glazing be assembled under vacuum? The vacuum being more insulating than the inert gases currently used... Only problem, the price that limits them for the moment to very specific applications such as classified buildings.
- At first glance, a vacuum insulation is hardly distinguishable from a traditional product.
- This is a plaque of silica powder amorphous pressed and wrapped with a metallized polyester film before evacuation.
- The whole, protected by an extruded polystyrene facing, offers a coefficient of thermal conductivity of 0.0052 W / m.K.
Domestic hot water (DHW): recovering calories
The heating becomes accessory, remains the question of the domestic hot water (ECS). Where will the calories come from to heat the water? Several types of high-performance equipment already exist: some use gas, others electricity. Some have matured while others are developing... As explained Jean-Christophe Visier, Director Energy-Environment at CSTB: "The conventional condensing boiler can hardly progress technically, but its price has become competitive.Inversely, the thermodynamic water heater will probably evolve strongly in the coming years.As the hybrid boiler".
Combining gas and electricity, it is in the form of an air-water heat pump integrated in a condensing boiler. It is a new product: its market is still embryonic.
- Thanks to a special exchanger, some floor elements can recover some of the calories contained in the water discharged by a shower. They are then used to preheat the arrival of water to the balloon.
More tracks to follow
The next step will be fuel cell cogeneration which manufacturers have been working on for years. This equipment transforms the energy released by a chemical reaction (which turns water into hydrogen) to produce electricity. It also has the advantage of recovering the calories released.
Stored in a buffer tank, they are then used to supplement the production of domestic hot water. A fuel cell would be able to save up to 40% of energy and significantly reduce CO2. But like any innovative solution, it is still expensive.
Another track, the domestic micro-cogeneration (MCHP). It is a system of small electric power (less than 36 kW), still stammering in France but which nevertheless offers a very high efficiency, of the order of 95 \%, or more if it is associated with a boiler 3rd generation condensing unit with Stirling type external combustion engine (slightly less with an internal combustion engine for CO2 more important). Micro-CHP, in addition to generating electricity, would reduce the primary energy requirement by 25% and CO2 up to 50% compared to separate production of heat and electricity.
Disadvantage: "With this technology, the kilowatts are longer to produce, so you have to store more and increase the volume of the buffer tanks", recalls Jean-Louis Rasmus.
The house without heating is not for tomorrow, but maybe for the day after tomorrow...
- In a micro-cogenerator, the calories provided by a condensing boiler are partly used to dilate helium. Cooled externally, it starts moving and actuates the piston of a Stirling engine.
- The latter in turn drives an alternator that produces electricity.
Heating and ventilation: a winning duo
In the context of a more energy-efficient habitat, ventilation plays a key role.
Thus, the dual flow VMCs reduce the heating requirements: the calories from the expelled air are recovered and transmitted to the fresh air filtered from the outside. The 3-in-1 versions are also capable of producing domestic hot water, and the 4-in-1 are able to cool the indoor air.
" With unparalleled flexibility "emphasizes Cécile Folachier, business manager thermal comfort at Aldes, a real plus." With rapid and brutal weather events, and in addition ever increasing demands of comfort, it is necessary to have a system that is as responsive as possible "she adds.
It's out of the question to bet on the inertia of the hydraulics, instead of the aerodynamics and its reaction time divided by 20. " Less expensive and less complex to implement, this type of installation is also less bulky. An asset again, when the price per square meter is high "she concludes.
The opinion of the expert *
" In the new and well-done renovation, energy consumption related to heating is no longer dominant. The stake is rather the electrical consumption: that of the equipments ensuring the production of sanitary hot water, the ventilation, the refreshment... Without forgetting the household appliances and the various apparatuses which surround us. "
Jean-Christophe Visier, Director Energy-Environment at CSTB (Scientific and Technical Center for Building).
- BEPOS: buildings with positive energy.
- Conductivity (lambda λ): this coefficient reflects the ability of a material to transmit heat. It is evaluated in watts per meter of thickness for a degree Celsius or Kelvin (W / m° C or W / m.K) of difference between the faces of the material. To be insulating (according to standard NF P 75-303), it must have a lambda at most equal to 0.065 W / m.K.
- NZEB (net-zero energy building): building with zero energy balance.
- R (thermal resistance): ratio between the thickness (e) of a material and its conductivity (λ) according to the formula, R = e / λ. The higher the result, the more insulating material.
- CAP: heat pump.
- Uw (thermal insulation coefficient): measures the heat loss of the chassis + glazing unit. The weaker it is, the more the joinery is insulating.