Aluminium window systems deliver many advantages, mainly the need for minimal maintenance like painting, durability, rigidity and minimal variability in the size (like swelling from moisture or expansion from heat) which is the problem with Timber & PVC windows.
The most common window in Australia is the Aluminium Window, to the point that 94% of all windows installed are aluminium – “but” they come with a downside.
They are great conductors of energy into and out of your building like all windows. Be it your house or your Commercial Building/Office, the most effective way of reducing the Heat Gain and Or Loss in and out of your building is by improving your window performance.
In the image above, the window on the left “is” thermally broken and the thermal imagery shows the glass and frame are the same or similar temperature (= colours). Whereas the window on the right shows “isn’t” thermally broken and there is a large variance between the frame and glass temperatures as seen by the purple and blue colours compared with the yellow and orange colours.
Windows are the heart and soul of a building. They let us connect to the outdoors and partake in the great outdoors lifestyle, which we have become accustomed to, here in Australia. Though, without addressing the insulation of windows in our building, we run the risk of costing ourselves a lot of money in either heating for places like Victoria and Tasmania and the Southern parts of New South Wales and/or cooling for places like Queensland and the Northern Parts of New South Wales.
The simplest way to improve Aluminium Windows thermally is firstly
1. Double Glazing them (including a Warm Edge Spacer) and
2. Thermally Break them.
Thermally Broken Aluminium window systems deliver most importantly, improved thermal performance. The advantages of aluminium are maintained – such as the strength, durability and stability – yet the drawback of thermal conductivity is overcome. This makes thermally broken aluminium windows, an ideal solution for commercial building applications and residential projects, where you may want large and complex glazing applications, Thermally Broken is your solution.
But what exactly is a thermal break and how does it work?
Thermally broken windows improve energy efficiency by controlling the forms of heat transfer. Heat or thermal heat energy can be transferred through material in three manners:
- Conduction is simply the process where heat is transferred through materials that touch one another.
- Convection is where gasses or liquids circulate to transfer thermal energy.
- Radiation transfers heat energy at a distance through high-frequency waves such as visible light, ultraviolet light or microwaves.
Thermally broken window frames are insulated against heat and cold conduction. This is done by separating the outside metal parts from the inside with a material that reduces the amount of heat or cold transferred through the frames. This feature is known as the “thermal break”.
A thermal break is a non-metallic resin or plastic material installed in the metallic window frame that physically separates the interior part of the window from the exterior part. Hence the pathway for heat energy to be transferred or conducted through the window frame is “thermally broken”.
A thermally broken window can be described as one in which the frame and sash components (members) have been split into interior and exterior elements and joined using a less conductive material. The formal definition of a thermally broken “Member” from the National Fenestration Rating Council (NFRC) is as follows:
Thermally broken (TB) members: system members with a minimum of 5.30mm separation provided by a low-conductance material (where thermal conductivity (is) less than or equal to 0.5 W/m.K or open-air space between the interior and exterior surfaces. Such systems include members with exposed interior or exterior trim attached with clips and all skip/debridged systems.
Countless companies in Australia now offer a comprehensive range of thermally broken aluminium windows and doors. These systems are locally designed and tested to maximise thermal performance and usually meet and exceed the required performance criteria for energy efficiency. These window and door systems deliver up to between 30% & 40% better efficiency than comparable double-glazed aluminium windows or doors.
The basis of the problem is, that most people don’t understand the correlation of the window performance, to the wall performance in a building. U-Value is for Window Performance and R-Value is for Wall Performance. Here is a table that I prepared, that explains it a bit better.