What to expect
| Typical duration | Roof 3–10 days · external wall system 2–4 weeks |
|---|---|
| Cost band | Figures live in the cost index |
| Permit required | External systems change appearance — controlled in designated settlements |
| Seasonal constraint | Year-round · best done alongside roof or render work |
Spend in this order
Owners frequently arrive with a plan to insulate the walls, which on this island is usually the third or fourth best use of the money.
- Roof. Largest solar gain surface, easiest to treat, biggest single comfort improvement. If the budget only covers one thing, this is the one.
- Shading. External shading over glazing stops solar gain before it enters the building. Internal blinds do not — by then the heat is already inside. Pergolas, deep reveals, shutters and planting are all cheaper than mechanical cooling.
- Glazing. Specification and orientation. A large west-facing pane is a heater from four o'clock in the afternoon.
- Cross-ventilation. Openings positioned so night air can actually move through the building purges the day's heat. This is free and it is designed in, not added.
- Walls. Worth doing, and it comes after the four above in return per euro on most properties here.
Thermal mass is already on your side
Traditional construction here — thick stone walls, vaults, and above all rock — has substantial thermal mass. It absorbs heat slowly through the day and releases it at night, which is exactly the right behaviour in this climate.
A cave house demonstrates the extreme case: surrounded by rock at a stable temperature, it stays remarkably cool through August with no cooling at all. That is not an argument against insulation everywhere, but it is an argument against wrapping a heavy traditional building in insulation without thinking, because doing so can cut it off from the mass that was doing the work.
External appearance in designated settlements
External wall insulation changes the thickness, the reveals and the finish of a building. In a designated traditional settlement that is a controlled change, and it may not be permitted in the form you want.
Internal insulation avoids the appearance question but reduces internal space, moves the dew point and needs careful moisture detailing on a traditional wall. Neither is automatically right — it depends on the wall, the settlement and how the building is used.
What this trade covers
- Roof and terrace insulation, integrated with the waterproofing build-up rather than bolted on afterwards.
- External wall insulation systems where the building and the settlement rules allow.
- Internal insulation with vapour-open detailing on traditional walls.
- Shading structures, pergolas and external shutters.
- Acoustic insulation, which matters more than owners expect in hotels and in party-wall properties in Fira.
- Coordination with the energy performance certificate where an upgrade is being documented.
Questions people actually ask
Will insulation make my house cooler in summer?
Roof insulation, yes, noticeably. Wall insulation on its own, less than people expect — because the heat is arriving mainly through the roof and through unshaded glazing. Shading is frequently the cheaper and more effective intervention.
Does a cave house need insulation?
Generally no. The surrounding rock provides remarkable thermal stability. The parts worth attention are the built face and any conventional structure attached to it, where the thermal performance is completely different from the excavated part.
Can I insulate the outside of a listed or protected building?
In a designated settlement, external wall insulation changes the appearance and is controlled. It may be refused. Internal insulation is usually the available route, with careful moisture detailing.
Will insulation cause damp?
It can, if the wrong system goes on a traditional wall. Insulating a wall that needs to dry outwards with an impermeable system moves the dew point and traps moisture. Vapour-open systems avoid this and cost more.
Is it worth insulating a property I only use in summer?
For a summer-use property, roof insulation and shading are worth it and heating-focused measures are not. The calculation is different again for a rental, where guest comfort in August is the entire product.