Haggini, Hi - couple of pointers, for the most part Northern European countries specify triple glazing but it's not cheap and Ireland is not per se a 'cold' country.
Low emissivity coating(s) applied to a window can increase the insulation factor as also argon gas (optimal spacing 1/2") separated by the pane(s) or better still the more expensive krypton gas having an optimal spacing of 3/8".
I don't know if you done the math or not but the pay off difference in a mild climate such as yours between double and triple glazing is negligible in terms of the energy expended and, all the more so if you add in low-e (emissivity coatings)
As spacings vary with type of gas so the window weight(s) need to be factored into the calculations with potential adverse impact on surrounding structural framework costs.
In summary, given Ireland's moderate climate triple glazing is very possibly not going to give you an ROI and it's probably best reserved for schools and hospitals where, it serves well as a noise pollution abatement solution derived from triple glazing's acoustical properties.
Hope it helps