How to carry out a successful energy renovation: a step-by-step guide

Why undertake energy renovation?
Energy renovation is a strategic investment for any homeowner. It offers many benefits that go far beyond the financial aspect. Let's take a closer look at the main reasons why you should undertake this type of work.
Reducing your energy bill
In France, heating is the biggest item of energy expenditure in a home, accounting for up to 60% of total energy costs. Good insulation of your building will considerably limit heat loss and therefore your energy consumption.
Thermal insulation plays a vital role in this reduction. For example, one extra degree of temperature is equivalent to 7-10% more consumption on your energy bill. So maintaining an average temperature of 19°C in your home is a good compromise between comfort and savings.
In addition to insulation, the installation of an efficient heating system or an intelligent thermostat also contributes to this reduction. This equipment allows you to rationalise your consumption by keeping your home at the right temperature, at the right time.
Improving thermal and acoustic comfort
A well-insulated house provides undeniable comfort in all seasons. Thermal insulation significantly enhances the quality of daily life by :
- Eliminating the feeling of cold near walls or windows in winter
- Keeping you cool in summer
- Eliminating unpleasant draughts
- Reducing humidity problems
At the same time, sound insulation plays an essential role in your well-being. Good sound insulation can reduce dissatisfaction with acoustics by more than 50%.
Insulation work can also create a healthier, more pleasant environment, with better regulation of humidity and improved indoor air quality.
Enhancing the value of your property
Investing in energy renovation considerably increases the value of your property. According to studies, energy renovation work adds between 2% and 11% to the sale price and between 1% and 5% to the rental price.
Even more impressive is the fact that properties rated A or B sell for twice as much as those rated F or G. On average, the price of a property increases by 5% for each letter of DPE gained.
The key stages in successful energy renovation
To achieve a successful energy renovation, it's essential to follow a methodical approach. Each stage helps to optimise your investment and maximise the effectiveness of the work. Let's take a look at the essential stages in transforming your home.
1. Carry out an energy audit
An energy audit is the essential starting point for any high-performance renovation. This in-depth diagnosis enables us to identify precisely the thermal weaknesses in your home. Unlike a simple DPE (Diagnostic de Performance Energétique), the energy audit offers a detailed analysis and personalised recommendations.
A full audit examines several aspects of your home:
- Insulation of walls, roof, floors and windows
- Heating and ventilation systems
- Domestic hot water production
- Consumption habits of occupants
To be reliable, this audit must be carried out by an RGE (Reconnu Garant de l'Environnement) certified professional.
2. Identify work priorities
Once the audit has been carried out, it is essential to establish a hierarchy for the work to be carried out. This is because some works generate more significant energy savings than others.
In order of effectiveness, the priorities are generally as follows:
- Roof insulation (up to 30% energy savings)
- Airtightness and ventilation (15 to 20% savings)
- Wall insulation (10-15% savings)
- Replacing windows (10-15% savings)
- Optimising the heating system (5 to 15% savings)
However, this prioritisation must be adapted to the specific condition of your home. For example, if your windows are particularly old, replacing them could become a priority, despite the theoretically lower energy savings.
3. Plan work in the right order
The order in which work is carried out has a major influence on its efficiency. Poor planning can lead to cost overruns or compromise final performance. A clear logic should therefore be followed.
Firstly, the insulation work must precede the sizing of the heating system. A well-insulated house needs less heating power. Installing an oversized boiler would be a waste of energy and money.
Secondly, external insulation should be carried out before internal insulation when both are required. This effectively eliminates thermal bridges.
In addition, ventilation renovation should be carried out at the same time as insulation work, to avoid damp problems. A house that is perfectly insulated but poorly ventilated can develop mould that is harmful to the health of the occupants and the durability of the building.
4. Choosing high-performance materials
The selection of materials is a crucial stage. Each component must be evaluated according to a number of criteria: thermal performance, environmental impact, durability and value for money.
For insulation, the lambda coefficient (λ) indicates the insulating capacity of the material - the lower it is, the better the insulation. Biobased materials such as wood fibre (λ = 0.038 to 0.042 W/m.K) or cellulose wadding (λ = 0.037 to 0.040 W/m.K) offer excellent performance while limiting environmental impact.
For windows, the Uw coefficient measures their overall thermal performance. For high-performance renovation, choose windows with a Uw value of less than 1.3 W/m².K, ideally with double or triple glazing depending on your climate zone.
As for heating systems, their efficiency is measured by their energy output. Air-water heat pumps have a COP (Coefficient of Performance) of 3 to 5, meaning that they produce 3 to 5 times more energy than they consume. Condensing boilers, with an efficiency of over 100%, are also an interesting option.
However, over and above theoretical performance, the quality of installation remains essential. An excellent material installed incorrectly will lose most of its effectiveness.
What work should be carried out to improve energy performance?
Improving the energy efficiency of a home involves several types of targeted work. The aim is to reduce heat loss while optimising energy production and management systems.
Roof, wall and floor insulation
Insulation is the cornerstone of effective energy renovation. The roof accounts for up to 30% of a home's heat loss, making it the absolute priority. The exterior walls, responsible for 20 to 25% of heat loss, come in second place. Finally, floors can account for 7 to 10% of energy loss.
For optimum results, insulate the roof first, then the cavity walls if your house has any. If this is not the case, insulation from the outside is preferable, unless there are specific planning constraints. As for floors, underfloor insulation is recommended if you have an accessible cellar or ventilated space.
Replacing windows
Windows are responsible for 10-15% of heat loss. Replacing them saves around 220 kWh per m² per year, or around €13.3 per m² per year for gas heating. New glazing offers much better performance: the inside temperature of double insulating glass reaches 17°C, compared with just 5.5°C for single glazing (at 0°C outside).
Installing an efficient heating system
A properly sized adapted heating system is essential. The condensing boiler uses the heat from the steam produced by combustion, achieving an efficiency close to 100%. At the same time, regular servicing ensures efficiency: once a year for combustion boilers and every two years for heat pumps.
Adding solar panels or a solar water heater
Solar thermal energy offers an economical and environmentally-friendly solution. A solar water heater can cover 50 to 80% of your annual domestic hot water needs. For a family of four, 2 to 4 m² of collectors are sufficient, depending on the region. A combined system can also contribute to heating, reducing consumption by 20-50%.
Installing an intelligent thermostat
Installing a programmable thermostat can save 5-15% on heating bills. Intelligent, connected models can increase this saving to 30%. One degree less represents around 7% energy savings. The ideal temperatures are 19-20°C for the living rooms, 18°C for the kitchen and 16°C for the bedrooms.
Properly planned and carried out, these various works will transform your home into a comfortable, energy-efficient space, while enhancing the value of your property.
How do you budget for renovation work?
Effective budgeting is a crucial stage in any energy renovation project. A well thought-out financial plan will help you avoid unpleasant surprises and optimise your investments. Let's take a look at how to draw up a realistic, controlled budget.
Estimating costs according to the surface area and condition of the property
The cost of energy renovation varies considerably depending on a number of factors. On average, the price per m² is between €200 and €450. For an overall renovation, you should expect to spend an average of €40,000, with a general range of between €20,000 and €60,000.
The initial state of your home has a major influence on the budget required. Light renovation work (painting, cladding) costs between €80 and €350 per square metre, while major renovation work including electrical and plumbing work can cost between €900 and €1,400 per square metre. For work involving major structural work, you should expect to pay between €1,000 and €1,300 per square metre.
The size of the property also plays a paradoxical role: proportionally, it costs more to renovate a small area than a large one. This is because certain costs, such as transporting machinery and protecting the site, remain fixed regardless of the size of the property.
Allow a margin for the unexpected
Professionals recommend that you systematically add a margin of 10-20% to your initial budget to allow for unforeseen circumstances. This precaution is particularly important for complete or structural renovations.
There can be many surprises: discovery of structural problems, delays in the delivery of materials, or the need for additional work that was not initially planned. Without this safety margin, you risk having to interrupt the work or compromise on quality.
In practice, if this margin isn't used in full to deal with unforeseen circumstances, you can always invest it in better quality equipment or finishes. In this way, this financial reserve is never lost - it contributes either to the peace of mind on the building site, or to the final improvement of your home.
How can you finance your energy renovation?
In Belgium, there is a wide range of grants available to encourage energy-efficient home renovation. Each region offers its own schemes:
- In Wallonia, the RénovEnergie awards cover a wide range of work (insulation, heating, ventilation...) and can finance up to 70% of costs, depending on income. An energy audit is often required.
- In Brussels, the primes Renolution group together aid for renovation and energy saving. They cover insulation, heating systems, ventilation and even joinery, and can be combined with tax reductions.
- In Flanders, the MijnVerbouwPremie centralises support for insulation, heat pumps, glazing, etc. A 0% energy loan of up to €60,000 is also available for eligible households.
In addition, a reduced VAT rate of 6% applies to renovation work in homes over 10 years old, subject to conditions. Some local authorities also offer local grants or additional loans.
Investing in your energy future
Energy renovation is undeniably a strategic investment for any homeowner. We have seen how this work can not only considerably reduce your energy bills, but also improve your day-to-day comfort.
Every step counts in this process. The energy audit, the cornerstone of your project, will guide you towards the priority interventions. Effective insulation, modern windows and an efficient heating system together form the basis of a successful renovation.
At first sight, the budget required may seem substantial. However, the many financial aids available make this work much more accessible.
As well as the immediate financial savings, don't forget the significant increase in the value of your property. A property rated A or B sells for twice as much as one rated F or G. So your current investment is transformed into future profits.
Finally, the environmental dimension should not be overlooked. Every energy renovation contributes to reducing greenhouse gas emissions. Your individual action therefore contributes to the collective effort to make the transition to a greener future.
The key to success lies in meticulous planning and the use of qualified professionals. Take the time to study the different options, compare quotes and find out about the grants available. Your home deserves this transformation, which will combine comfort, savings and respect for the environment.
Start your energy renovation project now. The benefits, both personal and global, await you at the end of the road.
Q1. What are the main benefits of energy renovation?
Energy renovation can significantly reduce your energy bills, improve the thermal and acoustic comfort of your home, increase the value of your property and reduce your carbon footprint.Q2. What is the first important step in energy renovation?
The first crucial step is to carry out a full energy audit of your home. This audit, carried out by a certified professional, identifies the thermal weaknesses in your home and defines the priority work to be undertaken.Q3. What are the most effective works to improve energy performance?
The most effective works include insulating the roof, walls and floors, replacing windows, installing an efficient heating system, adding solar panels or a solar water heater, and installing a smart thermostat.Q4. How do you estimate the budget needed for an energy renovation?
The cost of an energy renovation generally varies between €200 and €450 per m². For an overall renovation, allow for an average budget of €40,000, with a range of between €20,000 and €60,000. We recommend adding a margin of 10-20% for unforeseen circumstances.Q5. What financial assistance is available for energy renovation?
In Belgium, each region offers assistance for energy renovation: grants for insulation, heating or ventilation, reduced VAT at 6%, and even zero-interest loans in Flanders. An energy audit is often required to qualify.