Insulation in a Mediterranean climate
In a Mediterranean climate the priority is keeping solar radiation out rather than insulating against cold, so external shading of the openings delivers more per euro invested than any other measure.
gelisted editorial team · Updated 15 August 2026
The short version
- Glazed openings account for the largest summer heat gain.
- External shading is far more effective than internal blinds.
- Insulating the roof makes the biggest difference on a top floor.
- An energy certificate is compulsory to sell or let.
Traditional island architecture had this solved: thick walls, small openings and solid shutters. Recent construction forgot it, and air conditioning now compensates.
The right order of measures
First, solar shading of the openings, because a pane of glass receives far more energy per square metre in summer than a wall does. Second, the roof, which on a top floor is the surface most punished by the sun. Third, improving the joinery with thermal break frames and solar control glass. And last, the facade, the most expensive measure and the one that returns least in this climate.
| Measure | Indicative cost | Priority |
|---|---|---|
| Awning or external shutter | 150 to 600 € per opening | very high |
| Solar control glass | 300 to 800 € per opening | high |
| Roof insulation | 40 to 90 € per m² | high on a top floor |
| Thermal break joinery | 400 to 1,200 € per opening | medium |
| External wall insulation | 80 to 160 € per m² | medium |
| Cross ventilation at night | 0 € | very high |
| Planting for shade on the south facade | variable | high |
Why external shading wins
An internal curtain or blind stops the radiation after it has passed through the glass and entered the room, so the heat stays inside. An awning, an external shutter or a solid shutter stops it before it reaches the glass. That difference in position separates an effective measure from a decorative one, and it explains why traditional shutters remain the best solution in the catalogue.
The measure that costs nothing
Cross ventilation at night. Opening opposite windows between 23:00 and 08:00, when the outside temperature falls, discharges the heat stored in the building fabric and lets the day start several degrees lower. In homes with stone or marés walls, which carry substantial thermal mass, that cycle works especially well and cuts the hours of air conditioning needed the following afternoon.
Closing everything by day and ventilating by night reverses the usual habit and is exactly what traditional architecture did.
The energy certificate
It is compulsory to sell or let a home and must be handed to the buyer or tenant, with its rating shown in the advertisement. It costs 80 € to 250 € depending on floor area and its usual validity is 10 years. Beyond the formality, the report lists prioritised improvement recommendations, and in a Mediterranean climate those recommendations usually match the order set out here.
Frequently asked
+Which measure delivers most in this climate?
External solar shading of the openings, which stops radiation before it passes through the glass.
+Do internal curtains help?
Far less. They stop the radiation once the heat has already entered the room.
+What does roof insulation cost?
Forty to ninety euros a square metre, and it is a priority on a top floor.
+What can I do for free?
Cross ventilation at night between 23:00 and 08:00, closing the openings during the day.
+Is the energy certificate compulsory?
Yes to sell or let. It costs 80 € to 250 € and is usually valid for 10 years.
Sources
- 1Boletín Oficial del Estado, BOE (August 2026)
- 2Govern de les Illes Balears, Govern de les Illes Balears (August 2026)