Monty G said:
If given the choice you should opt for the soft-coat rather then hard-coat. Soft-coats give lower U-values which means less heat transfer – less increasingly expensive warm-air going out the window. Additional advantages are better clarity – K glass can show ‘haze’ under certain conditions, lower heat-gain – important in sun-rooms and large south-facing windows, and significantly UV transmission – less fading of fabrics and wooden floors.
As is clear from the thread there is a lot of confusion about the different coatings. Hard-coats (such as Pilkington ‘K’) are medium performance coatings. The tin-oxide coating is applied to the semi-molten glass and is ‘baked’ on. This ‘hard’ coated glass can be handled pretty much like any other glass and the coating can even be exposed and (gently) cleaned. Soft-coatings, typically silver-oxide, are applied to cold glass in a vacuum sputtering chamber. The coating is much finer then the hard-coats and requires more delicate handling. This results in only a couple of Irish IGU suppliers being equipped to deal with it at the moment It has been commonly available in northern Europe and north America for more then a decade.
As a rule of thumb a well made double-glazed soft-coated window will have a better energy performance then an un-coated triple-glazed window.
Anybody buying windows should ask for the whole window U-value and not just the glazing alone. Ask for independent certification as the sales people generally don’t know much about this and have a tendency to make things up as they go along.
Monty - this is excellent info. It rolls up very succinctly what I have found
by digging around and getting the info piecemeal from the suppliers.
Wrights in Milltownpass were helpful and gave me a lot of info similar to
what you have mentioned here. The only trouble is that they are too far
to be practical to fit/supply our windows.
My dilemma is that the supplier with best reputation locally just do
K-glass or something akin to hard coat/low E with no argon fill.
The other option is a much larger outfit who I've heard questionable
info regarding the standards of their fitters. They definitely do
soft-coat/low E and argon fill but I'm wondering if I'd risk getting
them to do the job because there is nothing worse than paying for
a high spec window and having it poorly fitted and having the
damp course material around the cavity destroyed by potentially
sloppy fitters,etc. Do you know of a supplier who will fit in Mayo
who does soft coat low-E. Drop me a PM if you do ! thanks!!!
-ipxl