How much do you really save with roof insulation?
By Capital Talent Invest Team · Published 2026-04-15 · 6 min read
Insulating attics is one of the most mentioned interventions in energy efficiency, but how much do you really save in annual euros? Beyond the generic 30% percentages, here we analyse concrete IDAE data and real cases in Castile and León.
Official data: between 20% and 30%
According to IDAE (Spanish Institute for Energy Diversification and Saving), proper attic insulation allows reduction of 20-30% of total household energy consumption. This range reflects variability between homes.
To understand: between 25-30% of a home's heat escapes through a poorly insulated roof. It's the first energy loss pathway, ahead of walls and windows.
Conversion to euros: concrete annual savings
| Home type | Annual bill before | After insulation | Annual savings |
|---|---|---|---|
| Apartment 70 m² | €1,800 | €1,350 | €450 (25%) |
| Apartment 100 m² | €2,400 | €1,700 | €700 (29%) |
| House 120 m² | €3,200 | €2,200 | €1,000 (31%) |
| House 180 m² | €4,500 | €3,000 | €1,500 (33%) |
| Chalet 250 m² | €6,000 | €3,900 | €2,100 (35%) |
These figures are statistical averages. Over 10 years, accumulated savings range from €4,500 to €21,000 — for a homeowner contribution of €1.
Factors determining real savings
- Climate zone: in zone E (León, Burgos), absolute savings are higher. In Castile and León, most homes are in zones D and E.
- Previous insulation status: a totally uninsulated home sees spectacular savings.
- Heating system: oil or direct electric heating sees higher absolute savings.
Indirect benefits: comfort and valuation
- Stable thermal comfort throughout the home.
- Energy rating improvement usually by 1-2 letters.
- Property valuation: according to Spanish Housing Ministry, +8-12% on sale price.
- Carbon footprint reduction: up to 1.5 tonnes of CO₂/year avoided.
Real cases in Castile and León
- Pérez family, Valladolid (apartment 95 m²): gas bill before €2,150/year, after €1,520/year. Savings: €630/year (29%).
- Mr Antonio, Palencia (house 145 m²): combined bill before €3,600/year, after €2,340/year. Savings: €1,260/year (35%).
- Mrs Carmen, Salamanca (apartment 80 m²): bill before €1,900/year, after €1,460/year. Savings: €440/year (23%).
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