Oxfordshire High Performance Renovation

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The Aluminium-clad Rationel FormaPlus is designed to suit a more traditional style of home, without compromising on the performance of a modern window. Despite being classical in appearance, FormaPlus windows can reach a low U value of 0.8 in triple glazing.

This building was originally a school house dating from the early 1900s. The classic looks of the FormaPlus were perfect to produce a maintenance free installation – only requiring washing.

One of the reasons why older windows, with multiple astragal bars on each window, are poorly insulated is because each bar separates two individual panes of glass. This creates many points where the unit must have additional seals. In contrast, each sash of these Rationel windows are a single sealed glass unit. To give the appearance of separate panes, spacer bars are inserted within the glass unit before the sealing process. Then the decorative bars are adhered to both sides.

On the other hand, it was decided that patio doors should not contain the same glazing bars. Since they are a more modern invention, there is not the same architectural background as a window with Georgian bars. By leaving the bars out, the customer enjoys a better view through the doors and the room benefits from more light.

Further thought went into the frames themselves: where fixed windows were manufactured to look identical to an opening sash in the same unit. From the outside, it is virtually impossible to tell the difference – giving the benefit of consistent and symmetrical frame widths throughout. Indeed, the presence of a handle on the inside is the only difference.

Bringing together all of these details with a matte 30% gloss paint finish and an installation featuring a combination of expanding foam and expending tape (for a seal that works with the building) meant we could maintain the classic aesthetic of a property whilst significantly enhancing its thermal performance.