The new lift and slide door “aluplast HST 85 mm” are unique in the market: they are available in three different variants, depending on the requirements for thermal insulation: from the basic version, through the standard version, to the premium version that meets the highest requirements for homes passive.


Since the beginning of this year, a new HST 85 mm door system has been available, which is on the one hand an answer to the expectations of creating larger window constructions, and on the other hand by design changes and, above all, the possibility of using larger glass packages up to 51 mm wide, allows you to achieve above-average properties in the field of thermal insulation. A novelty in this segment is the modular nature of the structure, which allows three optional configurations of the product, depending on the expected thermal parameters.

HST 85mm Basic version

HST 85mm Standard version

HST 85mm Premium version

Thanks to the freedom to choose different combinations of profiles in the part of the door lintel and in the threshold part, we have the possibility of choosing between three options: Basic, Standard and Premium, which are addressed to different groups of customers with different requirements regarding thermal insulation.

ThresholdAlu / PVCAlu / PVC with thermal breakPlastic GFK, filled with foam
Guide railAluAluPlastic GFK
Reinforced2x a steel pipe with a rectangular cross-sectionAluminum with thermal breakAluminum with thermal break

Changes in the construction of profiles allowed for a significant improvement in thermal permeability of profiles, which depending on the chosen option allows to obtain a weighted average value of heat transfer coefficient Uf = from 1.5 W (m2 * K) in the Basic version, through Uf = 1.3 W (m2 * K) in the Standard version up to Uf = 1.1 W (m2 * K) in the Premium version. Despite their huge size, HST doors remain an effective barrier against heat escape. 

The table below presents the values of Uw heat transfer coefficient for example HST doors (SCHEMA A) with dimensions of 4000 x 2300 mm glazed with a double chamber glass with a heat transfer coefficient for the middle part of the pane Ug = 0.5 W (m2 * K) and Ug = 0, 7 W (m2 * K) and values of linear heat transfer coefficient of thermal bridge at the interface between the pane and the frame Ψ = 0.04 W (m2 * K).

Examples of values of the heat transfer coefficient of the HST door with dimensions of 4000 × 2300 mm.

Uf (weighted average value for the reference dimension acc EN14351-1+A1)1,5 W(m2 * K)1,5 W(m2 * K)1,5 W(m2 * K)
Uw (4000×2300 mm), with the glass having a coefficient of Ug =0,5 W(m2 * K)0,82 W(m2 * K)0,78 W(m2 * K)0,71 W(m2 * K)
Uw (4000×2300 mm), with the glass having a coefficient of Ug =0,7 W(m2 * K)0,98 W(m2 * K)0,93 W(m2 * K)0,87 W(m2 * K)


An unquestionable advantage of this type of patio doors are conceivable structures with a total spread of up to 6 meters and maximum dimensions of the wings that reach 3000×2500 mm. Turning the large handle down, from the closed position, raises the wing by a few millimeters, releasing the pressure of the gaskets and the ability to move the wings freely.

HST balcony doors can be found in at least several different versions and arrangements of the wings and non-opened parts. The variety of constructions is one of the undeniable advantages of this solution. The most popular HST door variations are:

  • 2-casement– with one or both movable wings
  • 4-casement – with two middle or all moving wings

Specialized window fittings guarantee that the wings move freely and without any resistance against the unresolved parts of the structure. In this solution, the seal is realized by means of integrated gaskets, which guarantees high tightness. Appropriate tightness of the space between the moving wings of the HST door, when they remain in the closed position, is ensured by a special arrangement of overlapping taps equipped with a rebate gasket system.

The drawing below tells almost everything about the advantages of the HST door in shaping the usable and residential area. Being an alternative to sliding doors, classic balcony doors open very quickly into the living space, determining possible solutions related to the interior design of rooms. Despite the greater depth of the building from the classic balcony doors, it is the HST doors that leave freedom to use the surface.

If we add an unlimited amount of daylight to the rooms through the huge glazed surfaces of the wings and the elimination of any communication barriers through the low-threshold door design, what can you expect more from the balcony door. In one phrase: