still a worthwhile investment.

As an additional note, it is worth checking where windows using inert or noble gas are manufactured. If you live at high altitude and install a model that was constructed near sea level, there is a much-increased risk of the window seals failing and allowing the gas to escape.

Different windows for different facings

If you're building a passive solar home, you don't want to keep all the sun's heat out. So why would you need low-e windows? Because they can work the other way around.

For locations where heat gain is a real problem, such as east- or west-facing windows in areas where the sun is hot early or late in the day, low-e windows can help keep out the extra heat while still providing plenty of light.

For south- and north-facing windows, low-e glazing works as well, but needs to be on the inner pane instead of the outer one. This way, the windows allow heat and light to enter but the low-e coating helps retain the accumulated warmth inside the building and provide extra insulation.

Remember to put the low-e glazing on the right side of the window: on the outside pane to keep heat out and on the inside pane to keep heat in!