A cost efficient choice for home improvements
Double glazed French windows are popular for their cost efficiency and another term used for it is insulated glazing which means two to three sheets of glasses are fitted into a frame having air within its panes allowing insulation, hence the name insulated glazing.
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Aside from that, thicker glass panes do not necessarily mean it will keep the heat inside, In fact, modern low-glass units are even better for this job than older thick paned glass.
It is best to understand that energy efficiency is not the only factor that made double glazing cost efficient. The more durable windows you install for your home the longer you will enjoy the benefits of it.
That is why, the best choice for double glazing windows would not depend on the cost but on its durability, quality and style.