Portholes are a very popular glazing option for garage doors. We offer three standard sizes of porthole windows along with the possibility to make custom size and shape windows. Many customers are asking for front doors with porthole windows to match the garage door design or just because they like the round shape. However, U-value requirements for garage doors are much lower than for front doors.
Making portholes for garage doors do not require warm edge space bars or even double glazing. Meanwhile, thermal insulation requirements for front doors are totally different. All new construction products must match requirements for sustainability, passive house, safety, security, and many more specifications. Therefore, front door glazing is not ‘a piece of cake’.
Triple Safety Glazing
Triple safety glazing integrated into door leaf must have a good appearance and serve for a lifetime. That’s why almost all aluminium front door manufacturers offer different sizes but only rectangular windows. And only very few can offer front doors with the portholes.
As you know, the warm edge space bar is an essential part of the glazing. Glass panes are separated and fixed together into a single glazing block by using space bars. Straight bars are perfect for rectangular shape windows. When it comes to the round shape, we must bend the bar to copy the shape of the window. Of course, the diameter must be big enough not to break the space bar. Unfortunately, front doors are up to 1.3 metres wide and the porthole could be approx. 50-60 cm in diameter. Accordingly, 60 cm diameter is not enough to turn a straight space bar into a circle without damaging it.
There is another option – to convert the round shape into a regular octagon, decagon, or even dodecagon shapes. Consequently, the more corners and sides you have the more pieces of space bars you must combine into one. You can imagine having 8, 10, or even 12 obtuse angle corners instead of 4 right angle corners for a standard rectangular shape. However, the increasing number of connection and adhesion points raises the risk of glazing block failure. It can lose its airtightness which means a significant loss of thermal insulation and the emerging of fog inside glazing. Moreover, if you create many space bar connection corners the inside of the gazing won’t look pretty enough. Accordingly, for triple glazing, we need to put two space bars.
As a consequence, we went somewhere in between. Unfortunately, we can’t disclose all the technological tricks. Anyway, our customers can enjoy having front doors with triple glazed portholes or custom shape windows. Using this way we can offer front door designs also for old buildings to get an old image with modern technologies. Undoubtedly ‘old-good’ appearance combined with modern performance will increase the life quality and property value.