Energy Balance of Coated Double Glazings

Dr. Norbert Wruk

Coated double glazing units are a very common
and cost effective way to reduce the energy
consumption of commercial and residential
buildings. Gas filling additionally improves their
thermal performance.
However, it is often disregarded, especially in resi-dential
applications, that the window is the only
ele- ment in the building which is also able to gain
en- ergy. Due to the high transmittance for solar
radia- tion, a properly designed window is able to
compen- sate for the heat losses. Even at high
latitudes con- siderable energy gains can be
made, at least for south facing windows. On the
other hand, the total solar heat transmittance can
be reduced to a com- fortable level, if required.
Therefore, not the product exhibiting the lowest U-value
or the lowest TSHT but the product offering
the best balance between heat loss and solar
energy gain for a given application is the most
appropriate.
In medium term, architecture will change in order
to minimise the energy demand for heating and
cool- ing of buildings by making optimum use of
the solar energy, which is collected through the
window free of charge.

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