TMT Composite® (Thermal Modified Timber) is the concept of Lacuna’s advanced heat-treatment, which we use on beech for the folding windows. No chemicals whatsoever, only heat, is used in the treatment. Through the TMT® process the timber obtain durability class 1, as teak, and a humidity of about 5.5%, making the modified timber very suitable for folding windows, as dimensional stability is extremely important for an airtight product that should not need adjustment during changing weather conditions (moisture / drought).

The TMT Composite® also provides much better insulation, as the wood cannot absorb moisture like untreated wood. The result is a folding window that lasts for many, many years.

We can also supply European oak and FSC certified sapele mahogany, without TMT Composite® treatment, oiled in a number of color tints.

In line with our principles, we only use environmentally friendly, water-based and proven durable paints. You can choose from a large number of RAL and NCS colors.

For items that are not particularly exposed, no paint treatment is required the first 25-35 years.

For our oil-treated mahogany or oak products, we use cold-pressed linseed oil that seals the wood surface much better than water or turpentine-based oils.
Please note that oil-treated products should be re-treated at least three times in the first year after installation. This will saturate the wood and prevent drying cracks. Subsequently, depending on how much the parts are exposed to the weather, they should be re-treated twice a year. We can now also offer a transparent UV surface treatment for our Sapelli mahogany and oak products. The UV surface treatment is similar to painting and the elements do not need to be treated for the first many years.

Modern buildings often have dark frames externally. Here often a lighter, possibly white colour is chosen internally. We can paint our folding windows in two or three colour combinations – also if desired, for example, oiled mahogany combined with a white colour.

We can also paint several types of texture as well as a colourless paint – like varnish.

Some options are:
1. Combination of RAL 9005/9010
2. Combination of RAL 7016/9010
3. Mahogany, combined with 9010 and linseed oil
4. Mahogany, oiled with cold-pressed linseed oil
5. Mahogany, with cold-pressed black pigmented linseed oil
6. Oak, oiled with cold-pressed black pigmented linseed oil
7. Oak, oiled with cold-pressed linseed oil 

It is possible to choose if your window should open into or out of your home.

There are numerous options and combinations when it comes to the number of leaves and the location of the master leaf. In order to be able to fold the door, an odd number of door leaves are required. This means that on a door with an odd number of leaves, all leaves fold to the same side. If the door has an even number of leaves, these will be divided so that an odd number of leaves open to each side.

A few opening options are shown below, with varying number of leaves.

Most of our windows are supplied to facades where low-energy glass in either two or three layers is selected. However, our doors can be supplied with many other types of glass:

• Low energy
• Noise reduction
• Safety (Toughened and/or laminated glass)
• Solar control
• Self-cleaning
• Translucent glass types
• Glass with integrated blinds etc.

Unlike most other Scandinavian manufacturers of doors and windows, the glass in a Lacuna folding window is fitted from the inside. The glass beads are thus well protected inside, giving a number advantages: less maintenance, as there are no external joints, and greater security against burglary, as the glass beads cannot be removed by intruders.

The majority of our customers choose a folding window without glazing bars or fillings.
The wide window leaves, in a very thin frame, give a stylish and simple impression.

Lacuna manufactures several different types of glazing bars and transoms. Most of the customers who want glazing bars in their outward-opening folding door choose 25 mm moulded bars with what we also call farmhouse profile on the inside. This design is also available in widths of 19mm, 36mm and 42mm. For all widths, an internal softline profile is also available, which gives a simple and modern impression that matches the style of new buildings. All of our glazing bars are externally tenoned in the frame (not glued to the glass) and cannot fall off.

As an alternative to the traditional glazing bars, we also offer Helima bars. There are bars built in between the glass panes. Thus, there are no bars on the outside or inside of the door. Helima is price-attractive and has a great advantage when it comes to cleaning. The bars are available in several widths: 18mm, 26mm and 45mm.

If you want wider posts, we also make 55 mm, 75 mm and 110 mm horizontal transoms. These are continuous and thus divide the glass in the door. The transoms are, of course, completely integrated into the design of the frame.

We want the door including ironmongery to stay beautiful without corrotion for its entire life. We know that there are many different conditions that affect ironmongery. Particularly coastal areas can be a challenge for the stainless steel, so all parts are therefore treated with protective oil. Lacuna recommends regular maintenance and washing to keep the ironmongery and door clean. All hinges and handles are made of stainless steel and are available in black, white or steel.

Please read our maintenance guide.