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Wooden window and French door u-values

With their unique textures, grain patterns, and natural sturdiness, wooden windows and French balcony doors are a popular favourite for new-builds and renovations alike. Here you will find the thermal u-values of our different wooden windows and French door profiles and the different timber types that they can be made from.

Also known as the heat transfer coefficient, u-values are measured in W/(m²k)  and define the amount of heat lost through the product each hour per square metre. The lower the value, the more energy-efficient the door or window and the less heat lost. Please scroll down to find the relevant u-value for the product's glazing, the Ug value, its Uf value for the frame, or the total Uw value.


Uw values profile Classic IV 68 and Rustikal IV 68

Spruce wood

Glass Ug value W/(m²k) Frame Uf value W/(m²k) Window Uw value insulating glass edge seal aluminium W/(m²k) Window Uw value insulating glass edge seal uPVC W/(m²k)
1.1 1.1 1.3 1.3
1.0 1.1 1.3 1.2
0.7 1.1 Not possible for this system. Not possible for this system.
0.6 1.1 Not possible for this system. Not possible for this system.
Table of Uw values for Classic IV 68 and Rustikal IV 68 profiles in spruce wood according to DIN EN ISO 10077-1, see comments 1) 2) 3)

Wood types pine, larch, meranti

Glass Ug value W/(m²k) Frame Uf value W/(m²k) Window Uw value insulating glass edge seal aluminium W/(m²k) Window Uw value insulating glass edge seal uPVC W/(m²k)
1.1 1.2 1.4 1.3
1.0 1.2 1.3 1.2
0.7 1.2 Not possible for this system. Not possible for this system.
0.6 1.2 Not possible for this system. Not possible for this system.
Table of Uw values for Classic IV 68 and Rustikal IV 68 profiles in pine, larch, meranti according to DIN EN ISO 10077-1, see comments 1) 2) 3)

Wood types oak, eucalyptus

Glass Ug value W/(m²k) Frame Uf value W/(m²k) Window Uw value insulating glass edge seal aluminium W/(m²k) Window Uw value insulating glass edge seal uPVC W/(m²k)
1.1 1.5 1.5 1.4
1.0 1.5 1.4 1.3
0.7 1.5 Not possible for this system. Not possible for this system.
0.6 1.5 Not possible for this system. Not possible for this system.
Table of Uw values for Classic IV 68 and Rustikal IV 68 profiles in oak, eucalyptus according to DIN EN ISO 10077-1, see comments 1) 2) 3)

Classic IV 68 - profile section

Rustikal IV 68 - profile section

Classic IV 78 and Rustikal IV 78

Uw values profile Classic IV 78 and Rustikal IV 78

Spruce wood

Glass Ug value W/(m²k) Frame Uf value W/(m²k) Window Uw value insulating glass edge seal aluminium W/(m²k) Window Uw value insulating glass edge seal uPVC W/(m²k)
1.1 1.1 1.3 1.2
1.0 1.1 1.2 1.1
0.7 1.1 1.0 0.9 (0.93)
0.6 1.1 1.0 (0.95) 0.9 (0.87)
Table of Uw values for Classic IV 78 and Rustikal IV 78 profiles in spruce wood according to DIN EN ISO 10077-1, see comments 1) 2) 3)

Wood types pine, larch, meranti

Glass Ug value W/(m²k) Frame Uf value W/(m²k) Window Uw value insulating glass edge seal aluminium W/(m²k) Window Uw value insulating glass edge seal uPVC W/(m²k)
1.1 1.2 1.3 1.2
1.0 1.2 1.2 1.2
0.7 1.2 1.1 1.0 (0.97)
0.6 1.2 1.0 (0.99) 0.9 (0.91)
Table of Uw values for Classic IV 78 and Rustikal IV 78 profiles in pine, larch, meranti according to DIN EN ISO 10077-1, see comments 1) 2) 3)

Wood types oak, eucalyptus

Glass Ug value W/(m²k) Frame Uf value W/(m²k) Window Uw value insulating glass edge seal aluminium W/(m²k) Window Uw value insulating glass edge seal uPVC W/(m²k)
1.1 1.5 1.4 1.3
1.0 1.5 1.3 1.2
0.7 1.5 1.2 1.1
0.6 1.5 1.1 1.0
Table of Uw values for Classic IV 78 and Rustikal IV 78 profiles in oak, eucalyptus according to DIN EN ISO 10077-1, see comments 1) 2) 3)

Classic IV 78 - profile section

Rustikal IV 78 - profile section

  1. Windows with a heat transfer coefficient of Ug < 1.9 W/m²K for the glazing may always be specified with the standard dimensions of 1.23 m x 1.48 m.
  2. According to DIN EN ISO 10077, Uw values < 1.0 W/m²K are shown with 2 decimal points.
  3. The Uw values given in brackets are not rounded and are for information purposes only.

On a window made of wood, the U w values are calculated using the individual U values of the window frame and glazing, as well as the heat loss at the edge of the glass. For the sake of comparison, a standard window size of 1230 x 1480 mm is usually used for the calculation, but it can generally be assumed that a larger window will result in a lower value.

A thermally separated edge seal along the insulating glass - the so-called "warm edge" - further improves the thermal insulation of the entire door.

The heat transfer coefficients of a window made of wood determine whether a window can be classified as suitable for passive houses. Energy savings not only protect the environment, they also make an immediate difference on your energy bill.

The difference between a Uw value of 3.5 and a value of 0.83 can make a difference of more than 1000 litres of heating oil per year for an area of 30 m².

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