Back to basics.

The idea of slim DGUs is - on the face of it - very attractive. The day someone invents a single sheet of transparent material to replace existing double-glazing will signal the end of a massive industry. However, until that day, double-glazing is a developed technology that looks simple but has a great deal of Technical Know-How behind it to make it work. Getting it wrong leads to tears, and there are more than fifty years of often-painful experience to look back on.

Let's start at the beginning:

The most important (and effective) bit of double-glazing is - by far - the second sheet of glass. Obvious enough, but the problems arise in keeping those two panes clean and dry for twenty- five years or more. Glass is not cheap, nor is the labour involved in fitting them, so prematurely failed DGUs are a disaster in every sense: For the customer: For the installer who has to replace them at his own expense, and may even be chased through the courts: For the reputation of the industry, which has a poor reputation at the best of times: and - not least - for mankind, now that the sheer COST of energy is understood. Glass is expensive stuff, made from molten sand, and perhaps coated with exotic and complex films. DON'T WASTE IT!