The design shown below is a true DIY double-glazed window. It can be built and maintained by a person of modest skill; and at minimal cost. If someone breaks the glass, it can be replaced with readily available glass sheets from a home-supply store. If it begins to collect moisture, the seals can be replaced and new desiccant can be added.
One often-mentioned disadvantage of an air-gap (instead of noble-gas filled) double-glazed window is the convective loss due to air circulating around in between the sheets of glass. Other gases may lower the convective losses due to higher mass, which leads to slower diffusion. However, I think that most older windows have long since lost whatever special gas filling they may have once had. Air-filled windows have the advantage that a normal person can replace glass and replenish desiccant without any special equipment.
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