Thermal Breaks in Windows

Written by danielle hill
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Thermal Breaks in Windows
Windows with thermal breaks offer improved insulation properties. (Jupiterimages/Goodshoot/Getty Images)

An excellent means of improving a window's insulating ability is with a thermal break, a small gap that separates the window frame into distinct interior and exterior pieces. Thermal breaks can offer improved insulation properties to wood, fibreglass or metal frame windows. The thermal break itself consists of a non-conductive material, such as plastic.

Thermal Breaks in Aluminum Frames

Aluminium-framed windows frequently have thermal breaks to counteract their relatively high heat conduction. Not only do regular aluminium frames permit excessive heat transfer, but they can cause a high degree of condensation, which can damage paint, curtains or trim mouldings. Nonetheless, aluminium frames are a popular material, as they offer several advantages over traditional materials such as wood. Aluminium frames require relatively little maintenance. They are strong and lightweight and they resist weathering. Aluminium frames may have thermal breaks made of stainless steel or of man-made materials. These thermal breaks can reduce aluminium framed windows' "U-factor," a measure of the window's overall heat loss. Thermal breaks make aluminium frames a viable option even in the coldest climates, where their high rate of heat transfer would otherwise make them an unsuitable building material.

Edge Spacer Thermal Breaks

In double or triple-glazed windows, where individual panes of glass are divided by a cushion of air or other gases, thermal breaks may also contribute to improved overall insulation. In these cases, a thermal break lines the edges of the glass panes, avoiding the problem of a "weakest link" effect, where the efficiency of the double-glazing would be compromised. Edge spacers may use a less conductive metal, such as stainless steel, or a thermoplastic compound which contains desiccant materials to reduce condensation problems. A third option uses silicone foam with desiccant, bonded to the glass with an adhesive material.

Thermal Breaks in Rolled Steel Frames

An older style of window frame uses rolled steel instead of aluminium or wood, particularly for industrial or urban applications. When installing new windows in historical buildings, renovators may opt to use modern versions of rolled steel windows, reproducing the original pane arrangements and sizes, as well as materials, to achieve an historically accurate effect. These modern rolled steel frames often feature energy-efficient design advances such as thermal breaks. Given the extremely thin profile of a rolled steel window frame, and its relatively high heat loss, when compared with double-paned windows, for example, the insulating improvement offered by thermal breaks is highly advantageous for retaining indoor heat.

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