gdzie:
d_i - thickness of partition material
λ_i - television of conductivity of material in W/mK

Example :
2(d1λ1) + (d2λ2) ≤ 0,007 W/K                  

The table below shows how particular types of frames fulfill the raised criterion:

It should be emphasised that the actual effect of a thermal bridge on the edges of combined panes mounted in windows depends on the type of distance frame, heat insulation of the central part of the combined pane and the depth of the pane seating in profile and the coefficient of heat penetration Uf of profile. Together with the increase in seating depth of the pane the proportion of heat loss of windows through the edge is reduced and minimises the possibility of the occurrence of water vapour.

The table presented below compares the coefficient Psi of the most popular bent corners warm distance frames* on the market with aluminium frames. This data is given on the basis of the IFT Rosenheim WA-08/1 guidelines drawn up on the basis of research conducted in 2008.
 

From the table above it is shown that the application of plastic or stainless steel warm frames reduces Psi coefficient to 30% in relation to panes with aluminium frames. The effect of this is an increase of window temperature from the side of the room on the contact of frame with combined pane.

With the effect that permissible relative air moisture, which in given conditions forms water vapour may due to the application of "warm frames" be higher by approx. 10-15% and shall not cause occurrence of water vapour condensation. The permissible external minimal temperature is also reduced, at which water vapour condenses on pane surfaces.


The table below presents an example of temperature breakdown on window surface from room side of various types of distance frame for Top-Glas Ug=1.1 4/16/4T Ar
 

Example of calculation of coefficient of heat penetration of window Uw.

Method of calculating coefficient of heat penetration of window Uw, in which the influence of the connection of the frame with the pane is taken into account is indicated in Standard PN-EN ISO 10077 in the form of the following formula:
 

Uw - coefficient of heat penetration of window [W/m²K]
Af - surface of frame
Uf - coefficient of heat penetration [W/m²K]
Ag - glazed surface w [m²]
Ug - coefficient of heat penetration of pane [W/m²K]
Lg - circumference [m] (edge of glass)
Ψ - Linear heat penetration of window [W/mK]

In order to introduce the above formula we present a calculation example for a single window O32 of dimensions 535 x 1435 mm. The window is executed from the three-cell PCV profile strip of a complete width of frame and window of 125mm.

For calculation the following assumptions are accepted:

A_f = 0,43 m²
U_f = 1,2 W/m²K
A_g = 0,3377 m²
U_g = 1,1 W/m²K
L_g = 2,94 m
Ψ_a = 0,06 W/mK (aluminium frame)
Ψ_b = 0,041 W/mK (Thermix TX.N)
Ψ_c = 0,044 W/mK (Termo TGI)
Ψ_d = 0,051 W/mK (Chromatech)
Ψ_e = 0,051 W/mK (Chromatech Plus)
Ψ_f = 0,041 W/mK (Chromatech Ultra)

Window with aluminium frame (a):
Uw,a = 1,39 

Window with Thermix TX.N frame (b):
Uw,b = 1,31 

Window with Termo TGI frame (c):
Uw,c = 1,32 

Window with Chromatech frame (d):
Uw,d = 1,35

Window with Chromatech Plus frame (e):
Uw,e = 1,35

Window with Chromatech Ultra frame (f):
Uw,f = 1,31

The results received indicate that the coefficient Uw of a window with a warm frame is improved correspondingly in relation to a window with an aluminium frame of:

• 6.1% for Thermix TX.N frame and Chromatech Ultra frame
• 5.3% for Termo TGI
• 2.9% for Chromatech Plus frame and Chromatech

Benefits summary

Making the choice of warm distance frames, included in the product range, we are concentrating on:

• ensuring long-term correct tightness of combined panes due to bend frames at corners,
• maximising savings of heat energy losses through reduction of thermal bridge connecting frame with pane,
• limiting the risk of water vapour condensation on edges of panes inside the room,
• problem free mounting of decorative window dividers.

Range offered

» see colours offered for warm spacerbars


Particular characteristics of frames offered

Distance frames offered by Press-Glas, besides the joint characteristics, depending on the requirements of clients, may be differentiated by other traits:

• Chromatech Plus and Chromatech frames are typified by higher tightness than plastic frames with stainless steel foil,
• Among the offered plastic frames Thermix TX.N and Chromatech Ultra has the best heat insulation and the greatest rigidity,
• steel frames possess the optimal coefficient of linear extension, which amounts to 9x10-6K-1. For comparison with the coefficient of glass this amounts to 12x10-6K-1. Thus steel and glass possess very similar coefficients of linear extension, which in practice results in minimal stress at the glass-distance frame border, and in consequence minimal frame bulging, caused by heating of combined panes. For example: combined pane of length 200 cm produced in temperature +20 ^oC been subjected to heating to temperature +80 ^oC shows the following linear extension:
  * glass – 1.08 mm/m;
  * stainless steel distance frame – 1.44 mm/m;
  * aluminium distance frame – 2.88 mm/m!!!
  Whereas between glass and a steel frame the difference in linear extension amounts to 0.36 mm, in the instance of the difference between glass and an aluminium frame, linear extension amounts to 1.8 mm. In connection with this, the application of a steel distance frame has a five times lower stress value at sealing edges of the panes in comparison with an aluminium frame.