Glazed units with warm edge

Until recently, aluminium spacer bars were generally used in double glazing.

However, with ever improving window frame and glazing heat conductivity coefficient values, aluminium bars were shown to be the weak point in glass unit construction.

Warm edge

Objectives

Aluminium has significantly greater heat conductivity than the remaining window components. The aluminium spacer bar around the edge of the pane is the last route of excessive heat penetration from the room to the exterior. This effect has been taken into account in the new approach to calculation of the coefficient U_w of the window and has been described with coefficient Psi (Ψ). The solution to this problem may be the application of a spacer bar – called warm edge*, executed from compound insulation material or fine steel.

Warm edge criterion according to EN ISO 10077-1

To the time of establishing clear criteria enabling the definition of the warm edge concept, many spacer bars in glass units were sold on the market, which were indeed warmer than aluminium bars however had incomparably worse properties than correct solutions. According to this bars with improved design standard parameters are those, in which the spacer bar fulfils the following inequality:

Σ (d_iλ_i) ≤ 0,007 W/K

where:

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 bars fulfill the raised criterion:

Types of bars	Value ∑ (d_i x λ_i) EN ISO 10077-1	Qualification assessment of spacer bar as “warm edge”
Aluminium	0,1120	negative
Stainless steel Chromatech	0,0052	positive
Chromatech Ultra	0,0026	positive
Termo TGI	0,0020	positive
Swisspacer Advance	0,0019	positive
Swisspacer Ultimate	0,00002	positive
Multitech	0,00002	positive

It should be emphasised that the actual effect of a thermal bridge on the edges of glass units mounted in windows depends on the type of spacer bar, heat insulation of the central part of the glass unit and the depth of the pane seating in profile and the coefficient of heat penetration U_f 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 in corners warm edges* on the market with aluminium spacer bars.

U_g	Construction of glazed units	Window Frame	Type of spacer bar	Psi factor
1,1	4/16/4T Ar	PVC	Aluminium	0,065³
0,7	4T/12/4/12/4T Ar	PVC	Aluminium	0,066³
1,1	4/16/4T Ar	PVC	Stainless steel – Chromatech	0,051¹
0,7	4T/12/4/12/4T Ar	PVC	Stainless steel – Chromatech	0,050¹
1,1	4/16/4T Ar	PVC	Termo – TGI	0,040¹
0,7	4T/12/4/12/4T Ar	PVC	Termo – TGI	0,038¹
1,1	4/16/4T Ar	PVC	Chromatech Ultra	0,039¹
0,7	4T/12/4/12/4T Ar	PVC	Chromatech Ultra	0,037¹
1,1	4/16/4T Ar	PVC	Swisspacer Advance	0,039¹
0,7	4T/12/4/12/4T Ar	PVC	Swisspacer Advance	0,037¹
1,1	4/16/4T Ar	PVC	Swisspacer Ultimate	0,032¹
0,7	4T/12/4/12/4T Ar	PVC	Swisspacer Ultimate	0,030¹
1,1	4/16/4T Ar	PVC	Multitech	0,031¹
0,7	4T/12/4/12/4T Ar	PVC	Multitech	0,030¹
1,1	4/16/4T Ar	Wood	Aluminium	0,071³
0,7	4T/12/4/12/4T Ar	Wood	Aluminium	0,076³
1,1	4/16/4T Ar	Wood	Stainless steel – Chromatech	0,053¹
0,7	4T/12/4/12/4T Ar	Wood	Stainless steel – Chromatech	0,054¹
1,1	4/16/4T Ar	Wood	Termo – TGI	0,040¹
0,7	4T/12/4/12/4T Ar	Wood	Termo – TGI	0,039¹
1,1	4/16/4T Ar	Wood	Chromatech Ultra	0,039¹
0,7	4T/12/4/12/4T Ar	Wood	Chromatech Ultra	0,038¹
1,1	4/16/4T Ar	Wood	Swisspacer Advance	0,039¹
0,7	4T/12/4/12/4T Ar	Wood	Swisspacer Advance	0,037¹
1,1	4/16/4T Ar	Wood	Swisspacer Ultimate	0,031¹
0,7	4T/12/4/12/4T Ar	Wood	Swisspacer Ultimate	0,029¹
1,1	4/16/4T Ar	Wood	Multitech	0,030¹
0,7	4T/12/4/12/4T Ar	Wood	Multitech	0,028¹
1,1	4/16/4T Ar	Aluminium	Aluminium	0,080²
0,7	4T/12/4/12/4T Ar	Aluminium	Aluminium	0,110²
1,1	4/16/4T Ar	Aluminium	Stainless steel – Chromatech	0,068¹
0,7	4T/12/4/12/4T Ar	Aluminium	Stainless steel – Chromatech	0,066¹
1,1	4/16/4T Ar	Aluminium	Termo – TGI	0,049¹
0,7	4T/12/4/12/4T Ar	Aluminium	Termo – TGI	0,044¹
1,1	4/16/4T Ar	Aluminium	Chromatech Ultra	0,048¹
0,7	4T/12/4/12/4T Ar	Aluminium	Chromatech Ultra	0,043¹
1,1	4/16/4T Ar	Aluminium	Swisspacer Advance	0,047¹
0,7	4T/12/4/12/4T Ar	Aluminium	Swisspacer Advance	0,042¹
1,1	4/16/4T Ar	Aluminium	Swisspacer Ultimate	0,036¹
0,7	4T/12/4/12/4T Ar	Aluminium	Swisspacer Ultimate	0,031¹
1,1	4/16/4T Ar	Aluminium	Multitech	0,035¹
0,7	4T/12/4/12/4T Ar	Aluminium	Multitech	0,030¹

¹The data is given on the basis of the IFT Guideline WA-17/1
²The data according to guidelines EN ISO 10077 – 1:2007
³Data from the supplier aluminum spacer bar

DOWNLOAD PSI (Ψ) FACTOR DATASHEETS

Aluminium spacer bar – wood window frame

Aluminium spacer bar – PVC window frame

Chromatech spacer bar

Chromatech Ultra spacer bar

Termo TGI spacer bar

Swisspacer Advance spacer bar

Swisspacer Ultimate spacer bar

Multitech spacer bar

From the table above it is shown that the application of plastic or stainless steel warm spacer bars reduces Psi coefficient to 35% in relation to panes with aluminium spacer bar. The effect of this is an increase of window temperature from the side of the room on the contact of frame with glass unit. With the effect that permissible relative air moisture, which in given conditions forms water vapour may due to the application of “warm edges” 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 bar for U_g=1.1 4/16/4T Ar.

Test conditions	Type of window frame profile	Type of spacer bar	Temperature at edges of internal panes in glass unit [°C]	Δt the edge and in the middle of glass unitinternal pane [°K]	Moisture dew point at edge of internal pane [%]
External temperature 0°C internal temperature +20°C	Wood	Plastic	13,3	4,5	64,1
		Stainless steel	12,4	5,2	62,8
		Aluminium	10,8	6,8	55,7
	PCV	Plastic	13,2	4,7	64,3
		Stainless steel	12,5	5,3	62,3
		Aluminium	11,1	6,7	56,2

EXAMPLE OF CALCULATION OF U_w COEFFICIENT

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

U_w – coefficient of heat penetration of window [W/m²K]
A_f – surface of frame
U_f – coefficient of heat penetration [W/m²K]
A_g – glazed surface w [m²]
U_g – coefficient of heat penetration of pane [W/m²K]
L_g – 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 125 mm.

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 = 0,08 W/mK (aluminium)
Ψ_b = 0,051 W/mK (Chromatech)
Ψ_c = 0,044 W/mK (Termo TGI)
Ψ_d = 0,039 W/mK (Chromatech Ultra)
Ψ_e = 0,037 W/mK (Swisspacer Advance)
Ψ_f = 0,032 W/mK (Swisspacer Ultimate)
Ψ_g = 0,030 W/mK (Multitech)

Window with aluminium spacer bar (a):
U_w,a = 1,46

Window with Chromatech spacer bar (c):
U_w,b = 1,35

Window with Termo TGI spacer bar (b):
U_w,c = 1,32

Window with Chromatech Ultra spacer bar (d):
U_w,d = 1,31

Window with Swisspacer Advance spacer bar (e):
U_w,e = 1,30

Window with Swisspacer Ultimate spacer bar (f):
U_w,f = 1,28

Window with Multitech spacer bar (g):
U_w,g = 1,27

The results received indicate that the coefficient U_w of a window with a warm edge is improved correspondingly in relation to a window with an aluminium spacer bar of:

7,6% for Chromatech bar

10,0% for Termo TGI bar

10,3% for Chromatech Ultra bar

11,0 % for Swisspacer Advance bar

12,3 % for Swisspacer Ultimate bar

13,0 % for Multitech bar

Range offered

Standard offer

Type of spacer bar	Colour	Widths
Termo TGI	RAL grey 7035, 7040; brown 8003, 8016; black 9005; white 9016;	8, 10, 12, 14, 15, 16, 18, 20, 22, 24
Stainless steel Chromatech	natural	8, 10, 12, 14, 15, 16, 18, 20
Chromatech Ultra	RAL grey 7035, 7040; brown 8003, 8016; black 9004; white 9016;	8, 10, 12, 14, 16 18, 20, 22, 24
Swisspacer Advance	RAL light grey 7035; light brown 8003; black 9005; white 9016;	10, 12, 14, 15, 16, 18, 20
Swisspacer Ultimate	RAL light grey 7035; black 9005;	10, 12, 14, 16, 18
MULTITECH	light grey; black;	10, 12, 14, 16, 18

Offer avalaible for request with Sales Department

Type of spacer bar	Colour	Widths
Stainless steel Chromatech	black 9005	8, 10, 12, 14, 15, 16, 18, 20
Swisspacer Advance	RAL light grey 7035; light brown 8003; black 9005; white 9016;	8, 11, 22, 24, 27
Swisspacer Advance	RAL titanium (grey 9023); dark brown 8014; sulfuric 1016; yellow-green 6018; beige-brown 1011; pastel yellow 1034; grassy 6010; sapphire 5003; iridescent green 6026; brown-green 7013; beige 1001; ivory 1015; red-brown 8012;	8, 10, 11, 12, 14, 15, 16, 18, 20, 22, 24, 27
Swisspacer Ultimate	RAL light grey 7035; black 9005;	8, 11, 15, 20, 22, 24, 27, 32, 36
Swisspacer Ultimate	RAL titanium (grey 9023); white 9016; sapphire 5003; light brown 8003; dark brown 8014; sulfuric 1016; yellow-green 6018; iridescent green 6026; brown-green 7013; beige 1001; beige-brown 1011; pastel yellow 1034; grassy 6010; ivory 1015; red-brown 8012;	8, 10, 11, 12, 14, 15, 16, 18, 20, 22, 24, 27, 32, 36
MULTITECH	light grey; black;	8, 15, 20, 22, 24
MULTITECH	dark grey; white;	8, 10, 12, 14, 15, 16, 18, 20, 22, 24

Gallery of warm edges colours: Stainless steel Chromatech, Chromatech Ultra, Termo TGI and Multitech

Gallery of Swisspacer warm edges colours

Download application and watch gallery of warm edges on your mobile

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ADVANTAGES

Reduction of the linear heat leakage bridge on the edges of the glass unit

The properties of thermally insulated glass are also influenced by the linear heat conductivity on the edges. Up to now aluminium spacerbars have been commonly used, which are essential elements of glass units, but they have proved to be poor elements in making double glazed glass units. Aluminium is a much better carrier of heat than the remaining parts of the window construction, so the aluminium spacerbar is the final exit point for heat to move from the interior to the external area. The solution to this problem is to apply a spacerbar known as “ a warm edge”, which is made from highly insulating material or precious steel.

limitazione della presenza di vapore acqueo sui bordi interni del vetro (con l'utilizzo del distanziale)

Limitation of condensation of the edges of the glass unit

The solution to this problem is to apply the spacerbar known as “the warm edge”, which is made of highly insulating material or precious steel. The application of the warm edge improves the thermal insulation along the edges, which in turn increases the temperature in this area and reduces the risk of temporary water vapour condensation.