It is difficult to say clearly which window will be the better solution. It is worth making your own calculations and analyzing potential benefits and losses. There is no doubt that 3-pane windows are already a standard in energy-saving houses.
The heating energy demand of this type of buildings is very small and does not exceed 70 Kwh / (m2 x year). To maintain optimal results you need to invest in windows with a low heat transfer coefficient. Normal, double glazing would contribute to a noticeable increase in energy demand. Therefore, in this case they are strongly advised against – triple glazing
It is also worth emphasizing that triple glazed windows may meet the requirements of passive houses (the annual energy demand of these buildings may not exceed 15 Kwh / (m2 x year)). Modern technological solutions make the heat transfer coefficient of windows very low. PVC windows dedicated to passive houses can be quite expensive, but in this case the purchase will be profitable. An investment in high-end products can pay back after a few years of using a well-insulated building. Therefore, we can assume that a 3-pane window will be a good solution in new, energy-saving construction.
Standard double-glazed windows do not achieve such good parameters as their three-glazed counterparts. However, they can be successfully installed in homes with standard heat demand. Older single-family homes are often poorly insulated. In their walls there are numerous thermal bridges that increase energy demand. In this case, the investment in very tight, triple glazed windows may prove to be not very profitable. Even the most airtight glazing unit will not significantly reduce the building’s energy requirements if most of the heat escapes through walls or floors.
Therefore, the less insulated our building, the less investment in triple glazed windows will be. In some cases, it will pay for itself after several years of use (or not at all). We can therefore conclude that for standardly insulated buildings, good quality double-glazed windows are all we need. However, we should avoid the cheapest windows, which have a high heat transfer coefficient. Poor quality of their execution can cause that the energy demand of the building will be additionally increased.
Does the type of frame matter?
Certainly yes. It is not only about the heat transfer coefficient (it can be very similar). Utility values will be equally important. Both triple glazed and double glazed windows can have wooden, aluminum or PVC frames.
Wooden windows – they look very elegant and decorate the facade of the building. They do not heat up, thanks to which the profile does not show size variation. However, they require maintenance at least every five years. The commercial offers also include wooden and aluminum windows. It is an interesting window woodwork with good thermal insulation properties. We can successfully use it with larger window openings.
PVC windows – they do not look as representative as their wooden counterparts. However, they are slightly cheaper, provide good thermal insulation parameters, and at the same time guarantee a long service life. This type of window joinery requires no maintenance, which is its obvious advantage. Better quality products can be purchased with wood-like veneer, which effectively imitates natural wood.
Aluminum windows – are not very popular due to the higher heat transfer coefficient in the frame. They are a solution dedicated to large window openings. Aluminum window joinery is not often used in single-family housing. Much more often it is used in public facilities.
An interesting fact is that the profitability of the entire project is affected by the specificity of heating our building. Three-pane windows will be particularly cost-effective wherever we use heating with electricity, liquid gas and heating oil. Saving on heating energy will fall if our building is equipped with natural gas, pellet or wood heating. The lowest level of savings will be achieved with eco-pea and hard coal boilers. Of course, all calculations depend on the energy demand of the building. That is why it is worth making your own individual savings calculations.