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Heat losses through windows
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:
Planeparallel problem of heat transfer.
Geometry:
Given:
Temperature inside the room: T_{1} = +20 °C;
Temperature outside the room (ambient air): T_{2} = 32 °C.
Layer, material 
Layer thickness [m] 
Material density [kg/m^{3}] 
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 flux [W/m] through: 
Total [W/m] 
Wall 
Windows reveal 
Thermalconductive inclusions 
Monolayered brick wall 
22.5 (49%) 
17.1 (38%) 
5.9 (13%) 
45.5 
Multilayered modern construction 
5.0 (42%) 
4.3 (36%) 
2.5 (21%) 
11.8 
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Video.
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Reference
D.V.Kraynov, I.S.Safin, A.S.Ljubimcev, Calculation of additional heat loss through heatconducting inclusions (on the example of window reveal), Magazine of Civil Engineering, ¹6 (16), 2010.  p. 1722.