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Energy renovation: how to replace an old boiler?

Rising fuel prices have helped make energy-related spending one of the most important items for households. If the boiler is older than 15 years old or if it has not been well maintained, a change of equipment as part of energy retrofits can provide substantial savings while improving comfort. Major advances have been made by manufacturers over the last five years, and there are many ways to warm yourself more efficiently and more ecologically.

The useful efficiency of a boiler (or nominal efficiency) makes it possible to measure its efficiency: it corresponds to a ratio between the power consumed and the power returned. It is considered that when it is less than 75%, it is time to change equipment. This measure must be carried out by a professional heating engineer. A number of indicators should alert you to the status of the installation. This is the case, in particular, if we can no longer find the appropriate spare parts maintenance or if its fuel consumption becomes excessive (ie if, under equivalent conditions, it consistently consumes more than one year to the other) then no doubt, it's time to say goodbye to this old gas or oil boiler.
To fully benefit from the new system, it is imperative to ensure that the overall insulation of the home is performing well. If this is not the case, there will be no economic benefit from this new system.

The condensing gas boiler

The installation of a gas condensing boiler can make it possible to achieve 35% energy saving compared to a traditional boiler. Its principle is simple: the thermal fluid of the installation benefits from a free supply of calories thanks to the condensation of the steam of the fumes released by the combustion of the gas. The operation is carried out in a heat exchanger-condenser which takes care of recovering the calories and evacuating the condensates.
If the house is more than two years old and if it is a principal residence, it is possible to benefit from a tax credit (in 2018). In some cases, it is also necessary to take into account the renewal of the pipes and radiators (so that they are adapted to the new system) and a possible change of casing for the flue.

The wood or pellet boiler

Although the price of wood has increased significantly in recent years, it remains a cheap fuel whose energy efficiency is interesting. It is a significant competitor of gas in individual heating that can save up to 30% on energy bills. There are two types of wood boilers.

Log boilers and pellet boilers.
Both have the advantage of quickly heating the house, but the log boiler must be manually powered and therefore requires attention and a more sustained presence.

Pellet boilers
They can be powered automatically and a good adjustment of the equipment will achieve a long and economical burning time.
The price of a pellet boiler is higher than that of a log boiler, but state aid (tax credit, energy bonus or ANAH aid) or regional subsidies and the resulting savings will allow to make this facility profitable in about ten years.

The proximity of a wood processing area or a forest environment should be decisive criteria for this type of solution. By visiting the website of the National Forest Office or the Espace Info Energy website, it is possible to locate the nearest wood processing site. It will also take into account the space needed to store logs or pellets.

The heat pump

The heat pump (or heat pump) is not strictly speaking a boiler since it does not operate on the basis of combustion. It is nonetheless an interesting and very economical alternative that goes up to divide by three or four the amount of the bills. Its operation is based on capturing the calories contained in the outside air of the house to heat the water in the central heating system. It can be integrated into an existing gas boiler or oil boiler installation to complete it and lower the amount of the bill. The savings it allows are such that it is an initial investment quickly amortized.
If the heat pump as a rule produces more heat than is needed to make the central heating work properly, the winter temperatures do not surprisingly increase its consumption and lower its efficiency. Here again, the State may encourage the execution of works in the form of aid (tax credit, energy bonus or ANAH assistance).

Electric boilers

Under certain conditions, the electric boiler can be an interesting alternative. This is particularly the case when one can not benefit from a connection to natural gas, or when there is no storage space for wood or pellets. It takes a minimal place and therefore fits easily in studios or apartments. With good radiators, it is an effective solution, but the impact on electricity bills can quickly be a deterrent!

Hybrid or mixed solutions

Before deciding on the replacement of an old boiler, consider also the possibility of combining the energy sources with a hybrid boiler (especially with cogeneration) or mixed (by completing, for example, the installation with photovoltaic panels). A thermodynamic water heater or solar powered appliance saves on sanitary water production.

On the same topic

  • Questions answers
    • Questions on the interest of pellet boilers
    • Gas diagnosis of a boiler deemed non-compliant
    • How to improve the diffusion of heat in a house?
    • How to choose a reversible PAC?
    • Can we associate a gas boiler in CAP relief?
    • How to heat by geothermal energy?
    • How to change your boiler?
  • DIY tips
    • Why install a reversible heat pump
    • Benefit from aids for energetic renovation in 2018
    • Central heating: different types of boilers
    • The different types of auxiliary heating
    • The different types of electric heating
    • Installation of a central heating radiator
    • Wood heating: efficiency and heat production
    • Determine the origin of a central heating malfunction
    • Heat pump (PAC): aerothermal

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