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Wärmedurchlass

Wärmedurchlass is a term used in building physics to describe the transfer of thermal energy through a material or construction boundary caused by a temperature difference between its sides. It is a key concept for assessing the thermal performance of buildings.

The process encompasses conduction through solids, convection at air interfaces, and radiative heat exchange at surfaces.

Wärmedurchlass is used to evaluate insulation quality and energy efficiency of components such as walls, roofs,

The concept helps distinguish between the intrinsic insulating properties of materials (Wärmedämmung) and the overall heat

In
practice,
the
overall
heat
transfer
of
a
building
element
is
described
by
the
heat
flux
q"
(W/m^2)
and
the
overall
heat
transfer
coefficient
U
(W/(m^2
K)).
For
a
planar,
multilayer
element,
the
total
thermal
resistance
is
the
sum
of
the
resistances
of
each
layer
and
the
convective
resistances:
R_total
=
R_conv,in
+
sum(d_i/k_i)
+
R_conv,out.
The
relationship
between
U
and
R_total
is
U
=
1/R_total,
and
q"
=
U
ΔT.
windows,
and
doors,
and
to
calculate
energy
demands
or
certificates
for
buildings.
Calculation
methods
and
requirements
are
defined
in
standards
such
as
DIN
EN
ISO
6946
(overall
heat
transfer
coefficient)
and
DIN
EN
ISO
10211
(thermal
bridges).
In
German
practice,
U-values
are
a
central
parameter
in
energy
performance
regulations
and
building
codes.
transfer
of
a
assembled
element
(Wärmedurchlass),
which
depends
on
material
properties,
thicknesses,
and
boundary
conditions.