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Main > Application > Sample problems

Heat losses through windows

Calculation of the heat insulation of the building walls is an important stage of the design process. Additional heat losses arise from the thermal conductive inclusions such as interfloor bridging, window slopes, balcony plates, brackets of the system of the insulation facing and the other essential elements of the facade.
It is necessary to calculate these losses for accurate determination of the overall thermal resistance value.

Problem type:
Plane-parallel problem of heat transfer.

Geometry:

window block model

Given:
Temperature inside the room: T1 = +20 °C;
Temperature outside the room (ambient air): T2 = -32 °C.

Layer, material

Layer
thickness

[m]

Material
density

[kg/m3]

Thermal
conductivity

W/(m·K)

Cement

0.015

1800

0.93

Brick wall

Brick

0.64

1800

0.81

Modern construction

Aerated concrete

0.3

400

0.15

Insulation Rockwool FACADE BATTS

0.13

145

0.048

Plaster

0.12

1800

0.81

Task:
Calculate additional heat losses per length through the window slope for the monolayered brick wall and for multilayered modern construction.

Results:
Temperature distribution in the wall.

heat losses of the window block

Heat flux [W/m] through:

Total [W/m]

Wall

Windows reveal

Thermal-conductive inclusions

Monolayered brick wall

22.5 (49%)

17.1 (38%)

5.9 (13%)

45.5

Multi-layered modern construction

5.0 (42%)

4.3 (36%)

2.5 (21%)

11.8

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Reference
D.V.Kraynov, I.S.Safin, A.S.Ljubimcev, Calculation of additional heat loss through heat-conducting inclusions (on the example of window reveal), Magazine of Civil Engineering, 6 (16), 2010. - p. 17-22.