Triple glazing
A Triple Glazed Window as the name suggests consists of three panes of glass each
separated by an air gap. These air gaps provide the insulating layers which reduce
heat loss and prevent condensation. The effect of this additional layer is that
the Triple Glazed window is significantly better than double glazing. The energy
saving is increased as Triple Glazed Windows are considered to provide 60% better
insulation than a low-e argon filled double glazed pane. The radiation heat transfer
between the glass and the room is said to be 80% less.
At this moment in time, the use of Triple Glazing in the U.K is limited and the
fitting of it is considered by some to be 'overkill'. Not surprisingly it has found
greater use in colder climates particularly within the Scandinavian countries and
North America.
The cost of providing the additional panes of glass is in the order of 50 % more
than the cost of a double glazed unit. Having regard to the less cold weather conditions
in the UK it is perhaps necessary to ask whether the benefits achieved warrant the
additional expenditure involved. If you were to compare the financial savings accrued
from fitting triple glazing it is clear that despite obvious savings over and above
double glazing the savings are such that the additional expense could not be justified.
Substantial arguments have been put forward to justify triple glazing in the belief
that attaining a higher comfort level is the main benefit by maintaining a steady
temperature. Wolfgang Feist at a conference in Oxford produced a table showing what
the temperature differences were close to different forms of glazing when the internal
temperature is designed to maintain at around 21°C and the external temperature
drops to —5°C.
- next to a single glazed window, the adjacent temperature would be expected to be
around 1°C
- next to a double glazed window the adjacent temperature would be around 11°C
- next to a high specification low-e double glazed window, the adjacent temperature
would be 16°C
- whilst next to a triple glazed window, with a centre pane U value of just 0.65,
the temperature is 18°C.
We can see from these figures that there is an improving situation. These improvements
need to be judged against the relevant cost of the increased specification of each
system.
Where noise is a factor in considering the use of Triple glazing such as a building
situated near a busy road or under the flight path of a busy airport then the increased
expenditure may be justified as the level of noise is reduced significantly.
The thickness of the glass used is one of the key elements of the level of sound
insulation. Each thickness of glass will block out a different frequency, so a combination
of panes of different thickness is very effective at keeping noise out. This is
known as asymmetrical glazing. It should be mentioned that even the weight of the
glass plays a part since the compact mass reduces sounds.
A second key element is the size of the gap between the panes. The larger the gap,
the better the overall sound insulation effect. So by having a second gap, triple
glazing has a clear advantage over double glazing.
When considering the use of double or triple glazing therefore what should be borne
in mind is that Triple Glazing has obvious advantages over Double Glazing in terms
of energy efficiency. It has an even greater advantage when it comes to noise insulation.
However it is far more expensive and where financial considerations are crucial
there is an alternative namely secondary glazing which will provide an even greater
level of noise reduction because of the increased gap provided -at less cost
