Why insulating from the outside is the best choice
When renovating, insulation is key. It not only lowers your energy bills but also improves comfort. The important question is how to insulate.
-
Façade insulation: insulating from the inside causes loss of space and forces you to redo the entire interior finishing. Insulating in the cavity wall is rarely a good solution: often there is too little space, or the cavity is clogged with cement remains. External insulation is therefore the best choice: energy-efficient, durable and visually appealing.
-
Roof insulation: again, the best method is external insulation, using the sarking principle. The old roof covering is removed and insulation boards are placed on top of the structure. This creates a continuous insulation layer without thermal bridges and avoids additional interior finishing. Moreover, internal insulation may hide asbestos in the underroof – something you can eliminate with external insulation.
Subsidies make a difference
Today, investments in façade and roof insulation, windows and doors, or asbestos removal are eligible for attractive subsidies. Renovating truly pays off. You can read more about this in our article on renovation subsidies 2025.
Façade renovation: price ranges
The cost of façade renovation depends on the surface area, accessibility, number of windows and doors, and the chosen finish.
- Crepi with insulation: €120 – €150/m² (for façades from 100 m²).
- Spray cork with insulation: around €30/m² more than plaster.
- Brick slips or wood with insulation: at least twice as expensive as plaster. But it strongly depends on the chosen brick slip or type of wood.
- Brick motif (alternative to brick slips): price range between plaster and spray cork.
👉 Good to know: insulation thickness barely affects the price. For example, there is hardly any price difference between 10 or 12 cm of insulation.
Roof renovation: price ranges
Roof costs vary depending on the type, size and finish.
- Pitched roof insulation + concrete roof tiles: from €200/m² (simple roof of at least 100 m², excluding removal of the old roofing and old insulation).
- Flat roof insulation and waterproofing: about €150/m² (for simple roofs starting from 100 m²). Unit prices rise quickly for smaller roofs or those with skylights and corners.
- Luxury finishes (slates, etc.): significantly more expensive than concrete tiles.
Windows and doors: price ranges
Here too, the price depends on material, glazing and options.
- Material: PVC is the cheapest, followed by aluminium and then wood.
- Glazing: triple glazing costs more than double glazing but insulates better.
- Extras: ventilation, concealed hinges or roller shutters increase the price.
The more windows or doors you replace, the lower the unit cost.
Don’t forget extra costs
Besides the visible works, there are additional costs to consider:
- Installation of scaffolding
- Permits
- Waste containers and demolition works
- New rainwater downpipes, gutters, roof overhang cladding
- Window sills, plinths or roof edge finishes
- Extending electricity, relocating a lamp or other façade elements
A total renovation is always tailor-made, with the final cost depending on your choices and the size of the project.
At Cleys, we provide a personalised quotation and take care of the complete finishing.
Ready for a clear price estimate?
Would you like to know how much your total renovation will cost? Request a free quote from Cleys. Together we’ll assess your home, calculate the possibilities and prepare a proposal tailored to your needs.
