Countering heat build-up in dark coloured PVCu?

Over the last decade, one of the largest growth areas in the PVCu windows market has been the demand for colour. Dark colours are dominating the market with blacks, black browns and numerous greys being the most popular. These darker shades are however inherently subject to excessive heat build-up from direct sunlight which can lead to significant performance issues if not properly countered.

Sunlight is composed of UV, visible and Infrared (IR) light. The IR light does not influence the tone of the colour, but (is the key component of light energy that is most readily?) (can be) absorbed by the object and converted into heat energy.

For an object to appear black it must absorb practically the entire spectrum of the sunlight, and it is this absorbed light energy which is converted in to heat energy. In contrast, white shades will reflect the majority of the sunlight, meaning far less heat energy is absorbed and a much lower level of heat build-up results.

The high levels of heat build-up in darker colour shades will cause significant issues if not addressed. The increased temperatures will result in the expansion of components which will lead to issues such as windows & doors becoming difficult to open or close on hot days and in extreme cases permanent warping damage can occur. Larger items that are not reinforced, such as window cills, are especially prone to this problem.

The heat build-up effect in darker colour shades exposed to direct sunlight can lead to surprisingly high temperature increases in the PVCu above the ambient air temperature. This can be as high as +40°C on a hot summer’s day in the UK at 30°C; meaning the surface temperature of a south facing window might reach ca. 70°C! This is alarmingly close to the melting temperature of PVC of >85°C+ and it is not surprising that permanent distortion can occur at these elevated temperatures.

Thankfully, there are ways in which build-up of heat from direct sunlight be countered so that it does not lead to these excessive temperatures. By using IR reflective pigmentation in the coloured surface finish of the PVCu, the IR light within the light spectrum is reflected and the majority of heat-build-up effect can be avoided without effecting the visible colour of the surface.

Berger-Zobel, the manufacturer of ProKolor’s ZP range, have developed product formulations in the ZP 2400 series that use IR-reflecting pigments to resist heat absorption into dark colours. The Berger-Zobel “Anti-heat Technology” is used as standard in all dark colour shades to ensure that the substrates painted with ZP2400 are not subject to the excessive heat build-up typically associated with darker colours.

For more information on the heat build up performance of the ZP 2400 series coatings please see the following article – ZP 2400: Impact of Anti Heat Technology on Heat Build Up of Dark Colours

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