There are several factors that need to be considered when designing a shade structure. One of the most important aspects is the surrounding environment, which may include objects that could potentially cause damage to the structure or shade sail membrane, and impact the serviceable life of the material.

Knitted HDPE fabric from Gale Pacific can withstand climatic extremes across the globe. High Density Polyethylene (HDPE) shade fabric is a robust material with a broad service temperature; however, HDPE will begin to soften at 80°C and will melt when the temperature crosses 115°C.

What should you look for when installing shade structures utilising GALE’s knitted fabrics? Apart from obvious objects such as trees, vegetation and sharp objects, there are other elements that may not be as apparent at the outset – concentrated heat reflection sources, for instance.

Similar to how a magnifying glass reflects concentrated beams of sunlight directly onto a surface increasing its temperature, concentrated heat reflection from a number of sources on a shade sail can heat up the HDPE shade fabric, softening it and even melting it in extreme cases. Typically, these sources may include mirrors and polished metal surfaces, stainless steel slides and tables, metal signage or façades, and windows with reflective coatings (Low-E Glass).

Concentrated heat generated by reflected sunlight can result in temperatures much higher than direct sunlight; when these temperatures exceed 80°C, exposed materials such as shade fabrics can get damaged.


The damage caused by concentrated heat reflection is consistent with the appearance of melted plastic from alternate radiant sources of heat such as BBQs or outdoor heaters. Quite different from the effects of UV degradation, concentrated heat reflection can cause separation in the fabric with hard concentrated plastic around the outer area of the damaged area.

The damage will be localised on the shade fabric with minimal impact on the structural integrity of the adjoining area. However, the damage may appear to move along the surface of the fabric as the reflected heat follows the sun’s path over the course of the day.

Shade fabric

The impact of concentrated heat reflection is not common or isolated to HDPE shade fabric and is not covered by Gale Pacific’s warranty. The only way to prevent the possibility of future damage from this phenomenon is by giving due consideration to objects in the immediate environment when designing a shade structure.

Shade sail fabric

If damage due to concentrated heat reflection is detected during regular maintenance on your shade structure, it is important to identify the source of the heat and find a resolution prior to replacing the shade sail to avoid subsequent damage.