Old houses have charm but often poor insulation. In Luxembourg, where winters are harsh, good insulation can reduce your energy bill by 40-60%. Here’s how to proceed, step by step.
Why insulate an old house?
Financial benefits
| Situation | Annual heating bill | After insulation |
|---|---|---|
| Uninsulated house | €3,000-4,500 | €1,200-1,800 |
| Annual savings | - | €1,800-2,700 |
| Return on investment | - | 5-8 years |
Available grants
In Luxembourg, you can fund up to 70% of insulation work through grants:
- PRIMe House
- Klimabonus
- Municipal grants
Initial assessment: The essential step
Before starting, have an energy audit carried out to identify:
- Main sources of heat loss
- Priority interventions
- Improvement potential
- Required budget
Cost: €500-1000 (partially subsidised)
Priority insulation areas
1. The roof (30% of heat loss)
Heat rises: insulating the roof is priority number one.
Available options:
| Technique | Average cost | Performance | Work time |
|---|---|---|---|
| Loft insulation (blown) | €20-40/m² | ★★★★★ | 1 day |
| Converted loft (roll) | €40-80/m² | ★★★★☆ | 2-3 days |
| Sarking (external) | €150-250/m² | ★★★★★ | 1-2 weeks |
Our recommendation: Start with loft insulation if possible (best value for money).
2. Walls (25% of heat loss)
Three main techniques:
Internal wall insulation (IWI)
- ✅ Cheaper (€50-100/m²)
- ✅ No façade changes
- ❌ Loss of living space
- ❌ Possible thermal bridges
External wall insulation (EWI)
- ✅ No loss of space
- ✅ Eliminates thermal bridges
- ✅ Includes rendering
- ❌ More expensive (€120-200/m²)
- ❌ Changes external appearance
Cavity wall insulation
- ✅ Quick and economical
- ✅ No visible changes
- ❌ Only if cavity walls exist
3. Windows and doors (15% of heat loss)
Priority: Replace single glazing with double or triple glazing.
| Type | Performance | Average cost/window |
|---|---|---|
| Standard double glazing | ★★★☆☆ | €300-500 |
| Enhanced double glazing | ★★★★☆ | €400-700 |
| Triple glazing | ★★★★★ | €600-1000 |
Tip: Seals and airtightness are as important as the glazing.
4. Floors (10% of heat loss)
Often overlooked, floors can be insulated:
- Ground floor: insulation under the floor
- Crawl space: insulation of crawl space walls
- Cellar: insulation of cellar ceiling
Respecting old buildings
Old houses have characteristics to respect:
Breathable materials
Choose breathable insulation (allows water vapour to pass):
- Wood fibre
- Cellulose wadding
- Hemp wool
- Expanded cork
❌ Avoid polystyrene on old walls (risk of condensation).
Ventilation
An insulated house must be well ventilated:
- Single-flow mechanical ventilation minimum
- Double-flow recommended (recovers 80% of heat)
Thermal bridges
Pay particular attention to:
- Wall/floor junctions
- Window surrounds
- Roller shutter boxes
Recommended work sequence
- Energy audit (understand priorities)
- Roof (maximum impact, simple work)
- Windows (immediate comfort)
- Walls (larger investment)
- Floor (if necessary)
- Ventilation (do last)
Budget and grants
Example for a 150m² house
| Item | Estimated cost | Grants (70%) | Remaining cost |
|---|---|---|---|
| Roof | €6,000 | €4,200 | €1,800 |
| Walls (EWI) | €25,000 | €17,500 | €7,500 |
| Windows (8) | €6,000 | €4,200 | €1,800 |
| Double-flow ventilation | €4,000 | €2,800 | €1,200 |
| TOTAL | €41,000 | €28,700 | €12,300 |
Return on investment: 5-6 years with energy savings.
Use professionals
Insulating an old house requires specific expertise. On tack.lu, find specialists who:
- Know techniques suited to old buildings
- Handle PRIMe House and Klimabonus applications
- Guarantee their work
Ready to insulate your house? Request your free quotes and find the best insulation specialists in Luxembourg.
