What you are really comparing
For a house in Barcelona or on the coast there is no single best material. You compare the finished window at its real size on five points: frame, glass, opening type, resistance to salt air and sun, and installation. A weak link in any one of them cancels out the rest.
The most common mistake is choosing from a profile sample in a showroom. A 20 by 20 cm frame corner tells you nothing about how a 4-metre sliding door facing south onto the terrace will perform.
Frame material
Thermally broken aluminium handles large sizes and slim profiles, needs almost no maintenance and suits panoramic glazing. Quality depends on the width of the thermal break and the coating, so "aluminium" can mean very different things from one supplier to the next.
PVC insulates well at a moderate price, but on large sashes the profile gets bulky, and dark colours heat up badly in strong sun. For bedrooms and utility rooms it is a sensible choice; for the glass wall of the living room, less often.
Timber and timber-aluminium give a warm look inside and good insulation. Solid timber needs its finish renewed regularly on sunny elevations; the version with an external aluminium cladding solves that, at a higher price.
The glass matters as much as the frame
A good frame with basic double glazing gives you neither warmth in winter nor coolness in summer. In Catalonia the main enemy is the sun, so on south and west elevations you look at solar-control glass with a low-emissivity coating: it lets light through and cuts part of the heat. On the north side the priority is different: insulation.
Laminated glass is needed wherever there is a risk of impact or break-in: low windows, terrace doors, the ground floor. It also dampens noise noticeably better, which matters for a house near a road. Triple glazing rarely pays off on the coast; the money is usually better spent on solar control and external blinds or louvres.
Opening type and large openings
A tilt-and-turn window seals against the frame all the way round and is best at keeping out air and noise. A standard sliding system is more practical on a terrace, but its seal is weaker. A lift-and-slide system raises the sash to open and lowers it onto the gasket to close, so it comes close to hinged windows for airtightness. For large openings onto the pool it is the first option to consider.
A panoramic terrace door raises another issue: the threshold. A recessed track with no step looks great, but it needs proper drainage; otherwise, in driving rain, water from the terrace ends up in the living room. That is solved in the floor and terrace design, not when you order the window.
Sea air, sun and shutters
In Castelldefels, the Garraf or the Maresme, salt air quickly eats through a weak aluminium coating and cheap hardware. Ask the supplier whether the profile finish is rated for a marine environment and what the hinges, handles and fixings are made of. Stainless steel hardware costs more but pays for itself within a few seasons.
External roller shutters or louvres stop summer overheating better than any glass. The shutter box above the window is a known cold bridge and a way in for noise, so it is insulated or built into the wall at design stage. If the shutters are motorised, the cable goes in before the walls are closed.
Installation and how to compare offers
A high-grade window fixed with nothing but expanding foam, no sealing tapes and no sill will leak air and water around its edges. Ask how the window is fixed, whether there is a sub-frame (premarco), which tapes go inside and outside, and who is responsible for the junction with the facade and reveals.
To compare, ask two or three suppliers to price the same windows for your house: the same sizes, the same opening types, the same glass. The offer should give the thermal transmittance of the whole window, not just the profile, plus the glass build-up, hardware, colour and installation. After that, the price difference is visible line by line.
We select and install windows as part of house builds and renovations, as on the private house with a pool we delivered between 2022 and 2024. Each project has one person in charge and runs in Russian or Spanish.