Why choose Avenir Renovations?
Why the attic is the weak point of the house
Located just under the roof, the attic absorbs all temperature fluctuations. Without insulation, it allows heat to pass through in both directions.
Heat escapes from above in winter
Warm air rises. If the attic floor or slopes are not insulated, it escapes continuously and the boiler runs to compensate.
Insulating this point directly reduces consumption and relieves the heating system, which works less and wears out more slowly.
Rooms overheat in summer
Under a south-facing tiled or slate roof, the attic temperature rises very quickly. The rooms just below become uncomfortable during heatwaves.
A dense insulation material, such as wood fiber or cellulose wadding, slows down this heat and keeps the upper floor cooler by the end of the day.
A volume waiting for a project
Properly insulating today prepares for a future bedroom or office in the attic without having to start over. Even without planned fit-out, insulation limits condensation and protects the framework from temperature fluctuations.
Our attic insulation techniques in Leuven
The technique depends on the use of the attic, the framework, and the condition of the roofing.
Why entrust the insulation of your attic to Avenir Renovations?
The insulation of your attic requires expertise tailored to the characteristics of your roof. Avenir Renovations supports you with effective solutions and careful execution.
Access, condition of the framework, signs of moisture, presence or absence of an under-roofing, existing insulation: we check everything before proposing a solution. Insulation placed against a leaking roof only hides the problem.
- Mineral wools for a good performance-price ratio
- Cellulose wadding or wood fiber for summer comfort
- PIR panels when the available thickness is limited
The thicknesses aim for the performances expected today in Flanders, not the minimums of twenty years ago. Under a south-facing roof, dense insulations that slow down heat in the afternoon are preferred.
The insulation of a lost attic is done from the access hatch, without crossing the rooms with bulky materials. For slopes, the upstairs rooms are protected and waste is removed every evening.
How much does attic insulation cost in Leuven?
The chosen technique, surface area to be treated, access, and type of insulation affect the amount. Our attic insulation price simulator gives you a first estimate. Prices include VAT, with a 6% VAT for a home over ten years old.
| Type of work | Factors affecting the price | Indicative price including VAT |
| Blowing insulation on lost attic floor | Blown thickness, access through the hatch | 20 to 40 € / m² |
| Roll or panel insulation on floor | Number of layers, circulation path | 25 to 50 € / m² |
| Raised circulation floor | Area to keep accessible for storage | 30 to 60 € / m² |
| Slope insulation with vapor barrier and finish | Thickness, plate finish, roof windows | 60 to 110 € / m² |
| Installation of under-roofing from the inside | Condition of the rafters, access | 35 to 60 € / m² |
| Sarking (insulation only, excluding covering) | Thickness, scaffolding, edges to adapt | 120 to 200 € / m² |
| Removal of old or contaminated wool | Area, presence of droppings or moisture | 8 to 20 € / m² |
The visit starts in the attic: we measure the insulation in place, check the under-roofing and the condition of the rafters. The estimate follows with two or three options when several techniques are possible.
Example: for a terraced house in Wilsele with a lost attic of fifty square meters, blowing cellulose to a thickness of twenty-five centimeters with a small circulation path often costs between 1,200 and 2,300 euros including VAT.
Steps and grants for insulating an attic in Leuven in 2026
The Flemish grant for roof insulation
Insulating an attic, either through the floor or slopes, falls under the roof category of Mijn VerbouwPremie. Since March 2026, only owner-occupiers in income categories 3 and 4, the most modest, can still benefit from it. The insulation must meet the minimum required thermal resistance, which the technical sheets provided at the end of the project can prove.
VAT, loan, and renovation obligation
For other households, the VAT rate of 6% on a property over ten years old and Mijn VerbouwLening, available to categories 2 to 4, remain useful levers. For a house purchased with an E or F label, attic insulation is generally the first measure that improves the EPC certificate.
Rules for rental properties
The Flemish regulation on housing quality imposes a minimum roof insulation requirement on rental properties. For a landlord, insulating the attic is therefore not just a matter of comfort: it is also a condition for the property to remain compliant.
No permit required to insulate an attic
Insulating an attic floor or slopes from the inside does not require any permission. A sarking generally does not require a permit either, unless it significantly alters the appearance of the roof from the street or concerns a protected building.
Technical guidelines for properly insulating an attic
The thickness of insulation to consider
Today, we aim for a high thermal resistance, around 4.5 m²K/W or more for a roof or attic floor. Depending on the product, this often represents twenty to thirty centimeters of mineral wool or cellulose, slightly less with PIR panels.
Insulating an attic without under-roofing
Insulation is still possible, but the insulation must be protected from rain driven by the wind and dust. An under-roof membrane is installed from the inside, between the rafters, or a new one can be placed during a roof renovation.
A dust-free cellulose blowing in the house
The machine stays outside and the cellulose is blown into the attic through a pipe. The living spaces are not affected, and the intervention generally lasts a day.
Before blowing, we protect recessed lights and electrical boxes in the ceiling of the upper floor, and we mark the hatch to find the circulation path.
The ventilation of the insulated attic
If we insulate the floor, the attic remains cold and must remain slightly ventilated. If we insulate the slopes, the volume becomes part of the heated house and the housing ventilation takes over.
Frequently asked questions about attic insulation in Leuven
Is it better to insulate the attic floor or the roof?
If the attic is only used for storage, insulating the floor is quicker and cheaper, as the area is smaller. If you plan to convert it into a bedroom someday, insulate the slopes instead: you avoid paying twice.
How much savings does attic insulation bring?
In a terraced house where the attic was not insulated, heating consumption often decreases significantly from the first winter. The investment, amounting to a few thousand euros, is generally one of the quickest to recoup in a renovation.
Can you insulate an attic yourself in Flanders?
It is possible for a simple attic floor, but the Flemish grant and compliant work require careful implementation. Common mistakes include a discontinuous vapor barrier, unprotected lights, and insufficient thickness.
What to do with old fiberglass insulation?
If it is dry and clean, we leave it in place and add a layer on top. If it is compressed, damp, or soiled, we remove it before installing the new insulation.
An insulated attic, often in just one day
For a lost attic, the intervention takes one day, with no dust in the living spaces. For slopes to insulate, expect three to five days depending on the area.
Request your free diagnosis. We come to see your attic and you quickly know what solution is needed.
Agency Avenir
Rénovations
for Attic insulation in Leuven
An expert to take charge of your renovation projects and guarantee deadlines, budgets and quality of all services.
