It is a scene we often find when we visit terraces that were enclosed years ago in Granada and Malaga: on a cold winter morning the aluminium frames are covered in droplets, the glass is fogged on the inside and a dark patch of mould is starting to appear in the corners. The owner enclosed the terrace to gain space, but hardly uses it: in winter it is cold and damp, and in summer it turns into an oven.
The cause is almost always the same: an enclosure built with aluminium profiles without a thermal break, what the trade calls a "cold series". In this article we explain what a thermal break is, why it prevents condensation and when it is worth choosing. It is the difference between simply covering a terrace and gaining an extra room in your home.
A thermal break is an insulating strip that separates the inner face of the profile from the outer face. The aluminium stops carrying cold or heat from outside to inside, and without that thermal shock there is no condensation.
Aluminium is an excellent material for windows and enclosures: it is strong, light and stable, and it allows slim frames and large panes of glass. But it has one characteristic worth understanding: it conducts temperature very well. If a solid aluminium profile touches the outside on one side and the inside on the other, the cold travels through the metal to the inner face with almost no loss.
That path through which temperature "leaks" is called a thermal bridge. In a cold-series window or enclosure, the whole profile acts as a bridge: in winter the inner face of the aluminium is almost as cold as the outer face, and in summer almost as hot.
The solution is simple in concept and precise in its engineering. The aluminium profile keeps the same shape, but it is split into two halves: one faces the outside and the other faces the inside. Between them sits an insulating strip, usually made of polyamide, which holds both halves together mechanically but does not let temperature through.
If we cut the profile and looked at it side-on, we would see something like this:
As a result, the inner face of the profile stays mild even when it is cold outside. The aluminium still provides its strength and its looks, but it no longer behaves like a radiator for the outdoors. It is the same principle used in the STRUGAL thermal break aluminium windows we install in homes, applied to a complete enclosure.
Condensation appears when warm, humid air touches a cold surface. As it cools, the air can no longer hold all its moisture and releases it as droplets on that surface. It is exactly what happens to a glass of cold water in summer.
In a cold-series enclosure, the cold surface is the frame itself and often the glass. Inside the enclosure people cook, dry clothes, breathe and keep plants: there is no shortage of moisture. When that air touches an ice-cold frame, condensation is inevitable. That is the familiar "sweating" enclosure.
With a thermal break, the inner face of the profile stays close to room temperature. Without a thermal shock between the air and the frame, there is no condensation. If the glass and the roof are insulated as well, the space behaves like the rest of the house.
Condensation runs down the frames and collects on the floor and in the tracks, causing stains and wear.
Repeated damp in corners, joints and walls encourages mould and leaves a musty smell that is hard to remove.
Whatever you heat in winter or cool in summer escapes through the frames. The room never feels comfortable.
In the end, the enclosed terrace becomes a storage room. The opposite of what you wanted when you enclosed it.
Not every enclosure needs a thermal break. The key is what you are going to use the space for. This comparison sums up the differences:
| Thermal break enclosure (glass room / veranda) | Cold-series enclosure | |
|---|---|---|
| Profile | Aluminium with thermal break | Aluminium without thermal break |
| Use | An extra room, liveable all year round | Covering an area: utility room, porch, large terrace |
| Comfort | Performs like the rest of the house | Not designed to match the home's temperature |
| Condensation | No condensation, no "sweating" | May condense on cold days |
| Roof | Insulated sandwich panel 50 to 80 mm thick, quiet in the rain | Varies with use |
| Typical uses | Extended living room, study, nursery, dining room | Utility room, drying area, entrance porch |
If you would like to see how we plan a complete glass room, with a technical survey and drawings, we explain it on our glass room page.
The cold series still has its place, and it does not always make sense to pay for performance you will not use. It may be enough when:
If, on the other hand, you plan to put in a sofa, a desk or a baby's cot, the answer is clear: you need a thermal break. We cover this in more detail, along with other options, in our guide to terrace enclosures.
An enclosure is a system, and its performance is set by its weakest element. A thermal break profile achieves little if the glass or the roof let the temperature escape.
A liveable enclosure uses double glazing with a cavity, often with low-emissivity or solar control coatings. In Andalusia solar control matters a great deal: the problem with many enclosed terraces is not the cold but the heat that comes in during summer. Choosing the right glass for the terrace's orientation is part of the technical survey.
The roof receives the most sun and is where most heat is lost in winter. In a thermal break enclosure we use an insulated sandwich panel 50 to 80 mm thick: it keeps out cold and heat and also dampens noise. Under a light roof without insulation, rain sounds like a drum; under an insulated panel, you barely hear it.
Junctions with the wall, the floor and the slab must be carefully sealed so that air and water find no way in. It is work you will not see, but it decides whether the enclosure performs.
A well-designed thermal break enclosure does more than prevent condensation: it reduces the home's energy losses and insulates against outside noise. It is the same logic we apply to windows, extended to a whole room.
Tecnisun is a two-person family business with more than 25 years in the trade: we started in 1999 in France, where the veranda is a long-standing tradition, and we have worked in Andalusia since 2011. For enclosure profiles we work with INSTALLUX, and we are official installers for STRUGAL, SAXUN and FAKRO.
You can see the full range of solutions we offer on our enclosures page.
Can a thermal break be added to an existing enclosure?
No. The thermal break is part of the profile itself, so it cannot be added later. If your current enclosure condenses, the solution is to replace the profiles; sometimes part of the structure or the roof can be reused, and we assess that during the technical survey.
Will a thermal break enclosure never condense?
Under normal use, a thermal break enclosure with good glass and an insulated roof does not condense on the frames. As with any room in the house, it is wise to ventilate if you generate a lot of moisture, for example when cooking or drying clothes indoors.
Does the thermal break make a difference in summer too?
Yes. The insulating strip blocks temperature in both directions: in summer it stops the heat of the outer profile from reaching the inside. Combined with solar control glass and an insulated roof, the space stays much cooler.
Do I need a permit to enclose my terrace?
It depends on the municipality, the type of enclosure and, in apartment buildings, the owners' association. An enclosure is a lightweight structure, but every case is different: we advise you on the paperwork your particular project needs.
Tell us about your space and how you would like to use it. The online quote is free and without obligation, based on your measurements and photos; the technical home visit has a cost, which we tell you before arranging it. You can also call us on +34 627 84 14 04.
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Free, no-obligation online quote with your measurements and photos. The technical home visit has a cost, which we tell you before arranging it.
