Lift and slide doors
HST 85 mm

The new aluplast HST 85 mm lift and slide doors are unique on the market: they are available in two different variants, depending on the requirements for thermal insulation: in the basic version and in the premium version, which meets the highest requirements for passive houses.


From the beginning of 2015, a new HST 85 mm door system has been available, which is, on the one hand, a response to the expectations of creating ever larger window structures, and on the other hand, through structural changes, and above all, the possibility of using wider glazing units with a width of up to 51 mm, allows to obtain above-average properties in terms of thermal insulation. A novelty in this segment is the modular nature of the structure, which enables any three product configurations, depending on the expected thermal parameters.

Thanks to the freedom to choose various combinations of profiles in the lintel part of the door and in the threshold part, we can choose between two options: Basic and Premium, which are addressed to different groups of recipients with different requirements regarding thermal insulation.

Changes in the structure of sections allowed for a significant improvement in the thermal transmittance of profiles, which, depending on the selected option, allows to obtain a weighted average value of the heat transfer coefficient Uf = from 1.5 W (m2 * K) in the Basic version to Uf = 1.1 W (m2 * K) in the Premium version. Despite its enormous size, HST doors remain an effective barrier against heat leakage.

The table below presents the values ​​of the heat transfer coefficient Uw for an exemplary HST door (SCHEME A) with dimensions of 4000 x 2300 mm, glazed with a two-chamber glass with a heat transfer coefficient for the central part of the glass Ug = 0.5 W (m2 * K) and Ug = 0, 7 W (m2 * K) and the value of the linear heat transfer coefficient of the thermal bridge at the junction of the glass pane with the frame Ψ = 0.04 W (m2 * K)


The undoubted advantage of this type of patio door are structures with a total span of up to 6 meters and the maximum dimensions of the wings, which reach the value of 3000x2500mm. By turning the large handle down from the closed position, the sash is raised a few millimeters, the pressure of the seals is released and the sashes can be moved freely.

HST balcony doors can have at least several different versions and arrangements of wings and non-opening parts. The variety of structures is one of the undeniable advantages of this solution. The most popular HST door diagrams are:

  • 2-section – with one or both movable leaves
  • 4-section – with two middle or all movable wings


Specialized window fittings ensure that the sashes slide freely and without the slightest resistance in relation to each other or in relation to the non-opening parts of the structure. In this solution, the sealing is realized by means of integrated seals, which guarantees high tightness. Adequate tightness of the space between the moving HST door leaves when they remain in the closed position is ensured by a special system of overlapping catches equipped with a system of rebate gaskets.

The figure below shows almost everything about the advantages of HST doors in shaping the usable and living space. As an alternative to sliding doors, classic balcony doors, after opening the sashes, go very deep into the living space, determining various possible solutions related to interior design. Despite the greater installation depth than classic balcony doors, it is the HST door that leaves more freedom in managing the surface.

If we add to this an unlimited amount of daylight reaching the rooms through the huge glazed surfaces of the sashes and the elimination of possible communication barriers through the low-threshold door structure, then what can you expect more from a balcony door?

In one word:


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